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Effects of chemical composition on drawability and mechanical properties of magnesium alloy wires
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Procedia Manufacturing 15 (2018) 341–348 Procedia Manufacturing 00 (2017) 000–000 www.elsevier.com/locate/procedia
17th International Conference on Metal Forming, Metal Forming 2018, 16-19 September 2018, 17th International Conference on MetalToyohashi, Forming, Metal Japan Forming 2018, 16-19 September 2018, Toyohashi, Japan
Effects of chemical composition on drawability and mechanical Effects of chemical composition on drawability and mechanical Manufacturing Engineering Society International Conference 2017, MESIC 2017, 28-30 June properties magnesium 2017, of Vigo (Pontevedra), alloy Spain wires properties of magnesium alloy wires Vladimir Stefanov Hristov*, Kazunari Yoshida
Vladimir Stefanov Hristov*, Kazunari Yoshida 4.0: Trade-off Costing modelsTokai forUniversity, capacity optimization in Industry 4-1-1 Kitakaname, Hiratsuka, Kanagawa, 259-1292, Japan Tokai University, 4-1-1 Kitakaname, Hiratsuka, Kanagawa, 259-1292, Japan between used capacity and operational efficiency Abstract Abstract A. Santanaa, P. Afonsoa,*, A. Zaninb, R. Wernkeb In recent years, in the manufacturing sector, magnesium is becoming very highly used material for the manufacturing of wires for a University Minho, 4800-058 Guimarães, Portugal In recentpurposes, years, in the magnesium is becoming very highly used for the manufacturing of wires for various but manufacturing due to its low sector, strength a vastof variety of magnesium alloys are material being implemented instead. This research b 89809-000 Chapecó, SC, Brazil various but of due to its low strengthUnochapecó, aof vast variety of magnesium alloys are being implemented instead. This research focuses purposes, on the effect chemical components alloying elements in magnesium alloys wires, considering the workability for focuses the effect of chemical of alloying elements incomparing magnesiumthem alloys wires, considering the workability cold wireondrawing of the materials components and their mechanical properties and to similarly drawn magnesium wires. for cold wire drawing of the materials and their mechanical properties and comparing them to similarly drawn magnesium wires. © 2018 The Authors. Published by Elsevier B.V. Abstract © 2018 The Authors. Published by Elsevier B.V. © 2018 The under Authors. Published by Elsevier B.V. committee of the 17th International Conference on Metal Forming. Peer-review responsibility of the the scientific scientific Peer-review under responsibility of committee of the 17th International Conference on Metal Forming. Peer-review under responsibility of the scientific committee of the 17th International Conference on Metal Forming.
Under the concept of "Industry 4.0", production processes will be pushed to be increasingly interconnected, Keywords: Wire Drawing; Magnesium Alloys; Chemical Composition; Drawing Limit information on Magnesium a real timeAlloys; basisChemical and, necessarily, more Keywords: Wirebased Drawing; Composition;much Drawing Limitefficient. In this context, capacity optimization goes beyond the traditional aim of capacity maximization, contributing also for organization’s profitability and value. Indeed, lean management and continuous improvement approaches suggest capacity optimization instead of 1. Introduction 1. Introduction maximization. The study of capacity optimization and costing models is an important research topic that deserves contributions practical and ratio theoretical perspectives. This1/3 paper and discusses mathematical Magnesiumfrom is aboth highthe strength/weight material with a density thatpresents of aluminium and 1/4a that of iron. It is a management high material with a density 1/3 and that TDABC). of aluminium and 1/4model that of It hasMagnesium a for good number of strength/weight positivebased attributes like good weldability, electroconductivity and biocompatibility, but model capacity onratio different costing models (ABC A generic hasiron. been has a good of positive attributes like and good weldability, electroconductivity and magnesium biocompatibility, unfortunately it was has used low strength, which hinders itstouse for strategies manufacturing. of the wires but are developed andnumber to analyze idle capacity design towardsMost the maximization of organization’s unfortunately it has low strength, whicharehinders its high use for manufacturing. Most and of the are produced wire drawing, andmaximization the wires requested strength andis high ductility to withstand breaking of wire value. Thebytrade-off capacity vs operational efficiency highlighted it ismagnesium shown thatwires capacity produced by wire drawing, and the wires are requested high strength and high ductility to withstand breaking of wire caused by vibrations and repeated bending [1]. But for many applications of magnesium wires, the material low optimization might hide operational inefficiency. caused by vibrations and repeated bending But for many applications magnesium wires, material low strength is Authors. insufficient, that is why usage different magnesium alloys is of recommended, also tothe further increase © 2017 The Published by Elsevier B.V.of[1]. strength is insufficient, that is why usage of different magnesium alloys is recommended, also to further increase their toughness cold wire drawing process committee is proposed. Peer-review underaresponsibility of the scientific of the Manufacturing Engineering Society International Conference their In toughness a cold wire drawing process is proposed.of different alloying elements in the magnesium alloys, six this study, to examine the possible usefulness 2017. In this study, examine possible of different alloying the magnesium alloys, and six different alloy wiretotypes were the selected, theyusefulness were processed to their drawingelements limit byinusing cold wire drawing Keywords: Cost Models; ABC; TDABC; Capacity Management; Idle Capacity; Operational Efficiency different alloy wire types were selected, they were processed to their drawing limit by using cold wire drawing and their mechanical properties and drawability assessed. their mechanical properties and drawability assessed. 1. Introduction * Corresponding author. Tel.: +81-463-56-1211; fax: +81-463-50-2086. The cost of idle capacity is a fundamental information for companies and their management of extreme importance * E-mail Corresponding Tel.: +81-463-56-1211; fax: +81-463-50-2086. address:author. [email protected] in modern production systems. In general, it is defined as unused capacity or production potential and can be measured E-mail address: [email protected] in several ways: tons of production, available 2351-9789 © 2018 The Authors. Published by Elsevier B.V.hours of manufacturing, etc. The management of the idle capacity 2351-9789 © 2018 The Authors. by Elsevier B.V. Peer-review under responsibility thefax: scientific committee * Paulo Afonso. Tel.: +351 253 Published 510of 761; +351 253 604 741 of the 17th International Conference on Metal Forming. Peer-review [email protected] responsibility of the scientific committee of the 17th International Conference on Metal Forming. E-mail address: 2351-9789 © 2017 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the scientific committee of the Manufacturing Engineering Society International Conference 2017. 2351-9789 © 2018 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the scientific committee of the 17th International Conference on Metal Forming. 10.1016/j.promfg.2018.07.228
Vladimir Stefanov Hristov et al. / Procedia Manufacturing 15 (2018) 341–348 Vladimir Stefanov Hristov/ Procedia Manufacturing 00 (2018) 000–000
342 2
1.1. Staging of experiment First, the materials used for this study were selected and their chemical composition is shown in Table 1. They Table 1. Chemical composition of tested magnesium alloys. [%]
Mg
Al
Zn
Mn
Cu
Ni
AZ31
Bal.
3.5
1.3
0.2
0.05
0.1
AZ61
Bal.
5.87
0.75
0.39
0
0.01
AZ91
Bal.
9.3
0.35
0.13
0.1
0.03
AM60
Bal.
6
0.1
0.35
0.01
0
AZX912 AMX602
Bal. Bal.
9.22 6.01
0.6 0.01
0.31 0.26
0.05 0
0.01 0
Table 2. Pass schedule of wire drawing process. Pass
Diameter [mm]
R/P [%]
Rt [%]
0 1 2 3 4 5 6 7 8
2.4 2.33 2.22 2.09 1.98 1.87 1.78 1.69 1.60
0 5.7 9.2 11.4 10.2 10.8 9.4 9.9 10.4
0 5.7 14.4 24.2 31.9 39.2 45 50.4 55.6
D1 2 𝑅𝑅𝑅𝑅/𝑃𝑃𝑃𝑃 = �1 − � � � × 100[%] D0
Dn 2 𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅 = �1 − � � � × 100[%] D0
(1)
(2)
Fig. 1. Diagram of wiredrawing process.
were chosen due to the distinct levels of aluminium, zinc and calcium in the alloys, which can be used to establish a relation between these elements and the changes in mechanical properties of the magnesium alloys. 1.2. Die angle Selection of the proper die angle is crucial for the success of any wiredrawing operation. Based on the fact that frictional work increases with small of the die angles and redundant work and the possibility of occurrence of
Vladimir Stefanov Hristov et al. / Procedia Manufacturing 15 (2018) 341–348 Vladimir Stefanov Hristov/ Procedia Manufacturing 00 (2018) 000–000
343 3
surface cracks (Fig. 2), a number of FEM analysis have confirmed that a balance between frictional and redundant work can be achieved through proper selection of the angle. The results are illustrated in Fig. 2. Considering that for this study the drawing speed was selected at 500 mm/min and the reduction per pass [R/P] is 10% and a resin lubricant AGP-H8, the most acceptable die half-angle is between 5 and 6 degrees and for our research it was decided to be a tungsten carbide die with half-angle at α=6⁰.
Fig. 2. Optimum die angle for wire drawing by FEM.
2.
Results and Discussion
In this section the experiments and methodology used to determine a relation between the chemical component and mechanical properties of the magnesium alloy wires are examined. 2.1. Mechanical properties of annealed tested materials First, the annealed magnesium alloy mother wires (diameter 2.4 mm) were tested using tensile test, in order to examine their mechanical properties prior to processing, the results are shown in Fig. 3 and Table 3. Table 3. Tensile strength and breaking strain by tensile test of mother wires. Tensile Strength [MPa]
Breaking Strain ε
Pure Mg
184.6
0.132
AZ31
316.4
0.198
AZ61
372.3
0.181
AZ91
391.7
0.093
AM60
373.7
0.175
AZX912
307.4
0.124
AMX602
317.8
0.159
344 4
Vladimir Stefanov Hristov et al. / Procedia Manufacturing 15 (2018) 341–348 Vladimir Stefanov Hristov/ Procedia Manufacturing 00 (2018) 000–000
Following this, the six magnesium alloy wires were drawn to their drawing limit and compared to the drawing of pure magnesium wires. Even though pure magnesium has the best ductility/strength ratio, all of the magnesium alloy wires have a higher tensile strength.
Breaking Strain Fig. 3. Tensile test of mother wires.
2.2. Effect of chemical components on drawability of magnesium alloy wires In Fig. 4, it can be seen that with the increase of aluminium content in the alloy, the drawing limit of the wires also lowers proportionally. After that, tensile test was conducted on the wires for each pass in order to examine the increase of strength and decrease of ductility of the wires during the drawing process.
Breaking Point Drawing Limit Feasible Wire
Fig. 4. Drawing limit of various magnesium alloy wires.
5 345
Vladimir Stefanov Hristov/ Procedia Manufacturing 00 (2018) 000–000 Vladimir Stefanov Hristov et al. / Procedia Manufacturing 15 (2018) 341–348
3 pass drawn wire
4 pass drawn wire
2 pass drawn wire 1 pass drawn wire
5 pass drawn wire
Annealed Mother Wire
Fig. 5. Stress/Strain curve of AZ31 for all passes.
2.3. Mechanical properties of drawn magnesium alloy wires From the stress/strain curve of AZ31 in Fig. 5, the gradual increase of tensile strength and decrease of the breaking strain of after cold drawing, can be observed, also the last passes before the drawing limit, there is a maximum of tensile strength that cannot be passed which is about 20% for AZ31. Tensile strength and breaking strain can be seen in Table 4, increase of tensile strength and decrease of ductility is gradual with all materials, with an increase of tensile strength between 5 - 22% from the mother wire. Analysis of the relationship of chemical components and the mechanical properties of the materials is a goal of this research, that is why several graphs were built to explain these factors. In Fig. 6, maximum tensile strength and the drawing limit were compared for the different amount of aluminium in the magnesium alloy wires. It can noticeable that the gradual increase of aluminium also gradually increases the maximum tensile strength of the wires and proportionally decreases the ductility, for the wires AZ91 and AMX602 and AZX902, the increase is lower, due to the low drawing limit. When we observe the drawing limit of the drawn wires, aluminium content also noticeably decreases the maximum number of passes before breaking, especially in the cases of AZ31, AZ61 and AZ91, in the other wires cases, the trend still keeps true, even though it varies due to the other elements present in the wires. Zinc contents also has small relation to the mechanical properties, by increasing ductility with its increase, but the tensile strength of the material declines. Table 4. Tensile strength and breaking strain of drawn wires for every pass. Pass
1
2
3
4
5
6
TS[MPa]
ε
TS
ε
TS
ε
TS
ε
TS
ε
TS
ε
AZ31
336
0.062
376
0.042
403
0.041
408
0.02
401
0.018
381
0.017
AZ61
361
0.06
420
0.034
425
0.022
468
0.027
275
0.017
AZ91
370
0.028
427
0.02
327
0.017
AM60
352
0.047
403
0.031
411
0.029
413
0.021
296
0.014
AZX912
299
0.064
341
0.035
378
0.023
324
0.013
AMX602
366
0.037
370
0.027
373
0.022
6 346
Vladimir Stefanov Hristov/ Procedia Manufacturing 00 (2018) 000–000 Vladimir Stefanov Hristov et al. / Procedia Manufacturing 15 (2018) 341–348
(a) Maximum Tensile Strength vs Al content AZ61 AZ31
400
0.07
AM60
AZ91
0.06
AMX602
350
0.05 0.04
300
200
0.03
Pure Mg
250 0
0.02 2
4 6 Al content in wires
8
10
Pure Mg
10
0.08
AZX912
0.01
Number of passes before break
450
(b) Drawing Limit vs Al content
0.09
Breaking Strain
Maximum Tensile Strength
500
64
8 AZ31
6
AZ61
AZX912 AM60
4 AMX602
31 24
2 0
45 39
AZ91
0
2
4 6 Al content in wires
8
10
Fig. 6. Relation between aluminium content and mechanical properties for drawn magnesium alloy wires: ■ Pure Mg, AZ31, AZ61, AZ91, ▲ AM60, ⅹ AZX912, ◊AMX602.
Furthermore, when following the tensile strength and elongation of the wires for every pass, there is a noticeable trend of increase of strength with a proportional decrease of the breaking strain of the materials. In Fig. 7, the trend can be seen, and also it is noticeable that towards the last passes of the drawing, the mechanical properties of the wires decline in both tensile strength and ductility. (a) AZ31
(b) 408
401
0.05
0.042
360
0.04
0.033 336
340
0.03 0.017
0.02
320 300
381
376
380
316 0
60
468
450
0.06
400
420
0.01
0.07
425
0.06
372
350
0.05
361
300
0.034
250
0.029
200 0.02
0.018 20 40 Total reduction [%]
0.08
500
0.06 Breaking strain
Tensile strength
400
AZ61
0.04
275
0.03
0.027 0.017
0.02 0.01
150 100
Breaking strain
403
0.062
0.07
Tensile strength
420
0
20 40 Total reduction[%]
60
0
Fig. 7. Tensile strength and breaking strain in every pass of the cold drawing process for AZ31 and AZ61.
2.4. Surface and cracks observation by microscope and SEM The decrease of ductility in the final passes of the magnesium alloy wires is a significant problem. That is why the surface area of the wires and was observed by SEM, the surface was also observed after polishing the wire and observing the closest area to the surface. As seen from the pictures in Fig. 8, the surface area seen from the inside of the wires has a significant number of cracks and defects. They appear due to the increase of hardness on the surface of the wires and the accumulation of shearing stress. That is why even though, the drawing limit of the wires is set between 3 and 6 passes, the last useable wire is at least one pass before the breaking point.
50µm Vladimir Stefanov HristovProcedia et al. / Procedia Manufacturing (2018) 341–348 Vladimir Stefanov Hristov/ Manufacturing 00 (2018)15000–000
AZ91
AM60
Crack
3477
Cracks
50µm
50µm
50µm Fig. 8. Surface cracks of drawn AZ91 and AM60 wires at 3rd pass.
After Scanning Electron Microscopy on the surfaces of the annealed mother wires and the drawn wires at 2.09 mm, the cold wire drawing seems to preserve the wire surface of the drawn wires. Mother wire
AZ31
Mother wire
AZ61
2.09mm
AM60
50µm
Mother wire
2.09mm
2.09mm
AZX912
500µm
Mother wire
AMX602 2.09mm
2.09mm
500µm
AZ91
500µm
500µm
Mother wire
Mother wire
2.09mm
500µm
500µm
Fig. 9. SEM images of drawn wire surface of magnesium alloy wires.
3.
Conclusion
After drawing six different magnesium alloy wires, by using cold wire drawing to their drawing limit and examining their mechanical properties, the following conclusions have been drawn:
Vladimir Stefanov Hristov et al. / Procedia Manufacturing 15 (2018) 341–348 Vladimir Stefanov Hristov/ Procedia Manufacturing 00 (2018) 000–000
348 8
1) By using 10% reduction per pass, a tungsten carbide die with a die half-angle α=6⁰, it was possible to draw, six different magnesium alloy wires, from a starting diameter of 2.4 to a total reduction between 30-45% by cold wire drawing. 2) Testing the drawn wires, proved was possible to build a graph following the increase of tensile strength in comparison to decrease of ductility which can be used for each of the examined wires. 3) After comparing the results of the testing between the different wires, the aluminium content of the magnesium alloy wires proves vital to the mechanical properties of the drawn wires, a relation could be established between tensile strength, breaking strain, drawing limit and the chemical composition of the material. 4) Examining the increase of tensile strength in the drawn wires for every pass a reciprocal relation can be establish with the decrease of maximum breaking strain for the same pass, there is also a significant decrease in mechanical properties towards the finishing pass. 5) When observing the area surface of the wires with a microscope, appearance of cracks and defects can be confirmed, which leads to drop in mechanical properties close to the finishing pass, also SEM images show that despite this, the drawn magnesium alloy wires up to the 3rd pass retain surface similar to the annealed mother wire Acknowledgement We would like to express our gratitude to Nito Seiko Co. and Kinomoto Shinsen Co. in Japan, for providing the testing materials and proving helpful during the process of our work. References [1] K. Yoshida, K Doi, Improvement of ductility of aluminum drawn wire by alternate drawing, Interwire 2013, (2014) 77–79. [2] K. Yoshida, Cold drawing of magnesium alloy wire and fabrication of micro screws, Steel Grips 2 Suppl. Metal Forming, (2004) 199–201. [3] K. Lange, Drawing and Ironing, In Handbook of Metalforming, McGraw-Hill Book Company, New York, (1985) 14–27. [4] K. Yoshida, Basis of plastic working, Sangyo-Tosho Publishing, (1988) 66. [5] E. Ayman, K. Katsuyoshi, I. Hisashi, U. Junko, K. Masahi, Mechanical characteristics of hot extruded non-combustible magnesium alloy using water atomized powder, JWRI, 37 (2008) 2. [6] GondaMetal - http://gondametal.co.jp/product_mag/material_kenzai/pdf/flame_retardance.pdf
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Procedia Manufacturing 00 (2018) 000–000 Available online atatwww.sciencedirect.com Available www.sciencedirect.com Procedia online Manufacturing 00 (2018) 000–000
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Procedia Manufacturing 15 (2018) 341–348 Procedia Manufacturing 00 (2017) 000–000 www.elsevier.com/locate/procedia
17th International Conference on Metal Forming, Metal Forming 2018, 16-19 September 2018, 17th International Conference on MetalToyohashi, Forming, Metal Japan Forming 2018, 16-19 September 2018, Toyohashi, Japan
Effects of chemical composition on drawability and mechanical Effects of chemical composition on drawability and mechanical Manufacturing Engineering Society International Conference 2017, MESIC 2017, 28-30 June properties magnesium 2017, of Vigo (Pontevedra), alloy Spain wires properties of magnesium alloy wires Vladimir Stefanov Hristov*, Kazunari Yoshida
Vladimir Stefanov Hristov*, Kazunari Yoshida 4.0: Trade-off Costing modelsTokai forUniversity, capacity optimization in Industry 4-1-1 Kitakaname, Hiratsuka, Kanagawa, 259-1292, Japan Tokai University, 4-1-1 Kitakaname, Hiratsuka, Kanagawa, 259-1292, Japan between used capacity and operational efficiency Abstract Abstract A. Santanaa, P. Afonsoa,*, A. Zaninb, R. Wernkeb In recent years, in the manufacturing sector, magnesium is becoming very highly used material for the manufacturing of wires for a University Minho, 4800-058 Guimarães, Portugal In recentpurposes, years, in the magnesium is becoming very highly used for the manufacturing of wires for various but manufacturing due to its low sector, strength a vastof variety of magnesium alloys are material being implemented instead. This research b 89809-000 Chapecó, SC, Brazil various but of due to its low strengthUnochapecó, aof vast variety of magnesium alloys are being implemented instead. This research focuses purposes, on the effect chemical components alloying elements in magnesium alloys wires, considering the workability for focuses the effect of chemical of alloying elements incomparing magnesiumthem alloys wires, considering the workability cold wireondrawing of the materials components and their mechanical properties and to similarly drawn magnesium wires. for cold wire drawing of the materials and their mechanical properties and comparing them to similarly drawn magnesium wires. © 2018 The Authors. Published by Elsevier B.V. Abstract © 2018 The Authors. Published by Elsevier B.V. © 2018 The under Authors. Published by Elsevier B.V. committee of the 17th International Conference on Metal Forming. Peer-review responsibility of the the scientific scientific Peer-review under responsibility of committee of the 17th International Conference on Metal Forming. Peer-review under responsibility of the scientific committee of the 17th International Conference on Metal Forming.
Under the concept of "Industry 4.0", production processes will be pushed to be increasingly interconnected, Keywords: Wire Drawing; Magnesium Alloys; Chemical Composition; Drawing Limit information on Magnesium a real timeAlloys; basisChemical and, necessarily, more Keywords: Wirebased Drawing; Composition;much Drawing Limitefficient. In this context, capacity optimization goes beyond the traditional aim of capacity maximization, contributing also for organization’s profitability and value. Indeed, lean management and continuous improvement approaches suggest capacity optimization instead of 1. Introduction 1. Introduction maximization. The study of capacity optimization and costing models is an important research topic that deserves contributions practical and ratio theoretical perspectives. This1/3 paper and discusses mathematical Magnesiumfrom is aboth highthe strength/weight material with a density thatpresents of aluminium and 1/4a that of iron. It is a management high material with a density 1/3 and that TDABC). of aluminium and 1/4model that of It hasMagnesium a for good number of strength/weight positivebased attributes like good weldability, electroconductivity and biocompatibility, but model capacity onratio different costing models (ABC A generic hasiron. been has a good of positive attributes like and good weldability, electroconductivity and magnesium biocompatibility, unfortunately it was has used low strength, which hinders itstouse for strategies manufacturing. of the wires but are developed andnumber to analyze idle capacity design towardsMost the maximization of organization’s unfortunately it has low strength, whicharehinders its high use for manufacturing. Most and of the are produced wire drawing, andmaximization the wires requested strength andis high ductility to withstand breaking of wire value. Thebytrade-off capacity vs operational efficiency highlighted it ismagnesium shown thatwires capacity produced by wire drawing, and the wires are requested high strength and high ductility to withstand breaking of wire caused by vibrations and repeated bending [1]. But for many applications of magnesium wires, the material low optimization might hide operational inefficiency. caused by vibrations and repeated bending But for many applications magnesium wires, material low strength is Authors. insufficient, that is why usage different magnesium alloys is of recommended, also tothe further increase © 2017 The Published by Elsevier B.V.of[1]. strength is insufficient, that is why usage of different magnesium alloys is recommended, also to further increase their toughness cold wire drawing process committee is proposed. Peer-review underaresponsibility of the scientific of the Manufacturing Engineering Society International Conference their In toughness a cold wire drawing process is proposed.of different alloying elements in the magnesium alloys, six this study, to examine the possible usefulness 2017. In this study, examine possible of different alloying the magnesium alloys, and six different alloy wiretotypes were the selected, theyusefulness were processed to their drawingelements limit byinusing cold wire drawing Keywords: Cost Models; ABC; TDABC; Capacity Management; Idle Capacity; Operational Efficiency different alloy wire types were selected, they were processed to their drawing limit by using cold wire drawing and their mechanical properties and drawability assessed. their mechanical properties and drawability assessed. 1. Introduction * Corresponding author. Tel.: +81-463-56-1211; fax: +81-463-50-2086. The cost of idle capacity is a fundamental information for companies and their management of extreme importance * E-mail Corresponding Tel.: +81-463-56-1211; fax: +81-463-50-2086. address:author. [email protected] in modern production systems. In general, it is defined as unused capacity or production potential and can be measured E-mail address: [email protected] in several ways: tons of production, available 2351-9789 © 2018 The Authors. Published by Elsevier B.V.hours of manufacturing, etc. The management of the idle capacity 2351-9789 © 2018 The Authors. by Elsevier B.V. Peer-review under responsibility thefax: scientific committee * Paulo Afonso. Tel.: +351 253 Published 510of 761; +351 253 604 741 of the 17th International Conference on Metal Forming. Peer-review [email protected] responsibility of the scientific committee of the 17th International Conference on Metal Forming. E-mail address: 2351-9789 © 2017 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the scientific committee of the Manufacturing Engineering Society International Conference 2017. 2351-9789 © 2018 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the scientific committee of the 17th International Conference on Metal Forming. 10.1016/j.promfg.2018.07.228
Vladimir Stefanov Hristov et al. / Procedia Manufacturing 15 (2018) 341–348 Vladimir Stefanov Hristov/ Procedia Manufacturing 00 (2018) 000–000
342 2
1.1. Staging of experiment First, the materials used for this study were selected and their chemical composition is shown in Table 1. They Table 1. Chemical composition of tested magnesium alloys. [%]
Mg
Al
Zn
Mn
Cu
Ni
AZ31
Bal.
3.5
1.3
0.2
0.05
0.1
AZ61
Bal.
5.87
0.75
0.39
0
0.01
AZ91
Bal.
9.3
0.35
0.13
0.1
0.03
AM60
Bal.
6
0.1
0.35
0.01
0
AZX912 AMX602
Bal. Bal.
9.22 6.01
0.6 0.01
0.31 0.26
0.05 0
0.01 0
Table 2. Pass schedule of wire drawing process. Pass
Diameter [mm]
R/P [%]
Rt [%]
0 1 2 3 4 5 6 7 8
2.4 2.33 2.22 2.09 1.98 1.87 1.78 1.69 1.60
0 5.7 9.2 11.4 10.2 10.8 9.4 9.9 10.4
0 5.7 14.4 24.2 31.9 39.2 45 50.4 55.6
D1 2 𝑅𝑅𝑅𝑅/𝑃𝑃𝑃𝑃 = �1 − � � � × 100[%] D0
Dn 2 𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅 = �1 − � � � × 100[%] D0
(1)
(2)
Fig. 1. Diagram of wiredrawing process.
were chosen due to the distinct levels of aluminium, zinc and calcium in the alloys, which can be used to establish a relation between these elements and the changes in mechanical properties of the magnesium alloys. 1.2. Die angle Selection of the proper die angle is crucial for the success of any wiredrawing operation. Based on the fact that frictional work increases with small of the die angles and redundant work and the possibility of occurrence of
Vladimir Stefanov Hristov et al. / Procedia Manufacturing 15 (2018) 341–348 Vladimir Stefanov Hristov/ Procedia Manufacturing 00 (2018) 000–000
343 3
surface cracks (Fig. 2), a number of FEM analysis have confirmed that a balance between frictional and redundant work can be achieved through proper selection of the angle. The results are illustrated in Fig. 2. Considering that for this study the drawing speed was selected at 500 mm/min and the reduction per pass [R/P] is 10% and a resin lubricant AGP-H8, the most acceptable die half-angle is between 5 and 6 degrees and for our research it was decided to be a tungsten carbide die with half-angle at α=6⁰.
Fig. 2. Optimum die angle for wire drawing by FEM.
2.
Results and Discussion
In this section the experiments and methodology used to determine a relation between the chemical component and mechanical properties of the magnesium alloy wires are examined. 2.1. Mechanical properties of annealed tested materials First, the annealed magnesium alloy mother wires (diameter 2.4 mm) were tested using tensile test, in order to examine their mechanical properties prior to processing, the results are shown in Fig. 3 and Table 3. Table 3. Tensile strength and breaking strain by tensile test of mother wires. Tensile Strength [MPa]
Breaking Strain ε
Pure Mg
184.6
0.132
AZ31
316.4
0.198
AZ61
372.3
0.181
AZ91
391.7
0.093
AM60
373.7
0.175
AZX912
307.4
0.124
AMX602
317.8
0.159
344 4
Vladimir Stefanov Hristov et al. / Procedia Manufacturing 15 (2018) 341–348 Vladimir Stefanov Hristov/ Procedia Manufacturing 00 (2018) 000–000
Following this, the six magnesium alloy wires were drawn to their drawing limit and compared to the drawing of pure magnesium wires. Even though pure magnesium has the best ductility/strength ratio, all of the magnesium alloy wires have a higher tensile strength.
Breaking Strain Fig. 3. Tensile test of mother wires.
2.2. Effect of chemical components on drawability of magnesium alloy wires In Fig. 4, it can be seen that with the increase of aluminium content in the alloy, the drawing limit of the wires also lowers proportionally. After that, tensile test was conducted on the wires for each pass in order to examine the increase of strength and decrease of ductility of the wires during the drawing process.
Breaking Point Drawing Limit Feasible Wire
Fig. 4. Drawing limit of various magnesium alloy wires.
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Vladimir Stefanov Hristov/ Procedia Manufacturing 00 (2018) 000–000 Vladimir Stefanov Hristov et al. / Procedia Manufacturing 15 (2018) 341–348
3 pass drawn wire
4 pass drawn wire
2 pass drawn wire 1 pass drawn wire
5 pass drawn wire
Annealed Mother Wire
Fig. 5. Stress/Strain curve of AZ31 for all passes.
2.3. Mechanical properties of drawn magnesium alloy wires From the stress/strain curve of AZ31 in Fig. 5, the gradual increase of tensile strength and decrease of the breaking strain of after cold drawing, can be observed, also the last passes before the drawing limit, there is a maximum of tensile strength that cannot be passed which is about 20% for AZ31. Tensile strength and breaking strain can be seen in Table 4, increase of tensile strength and decrease of ductility is gradual with all materials, with an increase of tensile strength between 5 - 22% from the mother wire. Analysis of the relationship of chemical components and the mechanical properties of the materials is a goal of this research, that is why several graphs were built to explain these factors. In Fig. 6, maximum tensile strength and the drawing limit were compared for the different amount of aluminium in the magnesium alloy wires. It can noticeable that the gradual increase of aluminium also gradually increases the maximum tensile strength of the wires and proportionally decreases the ductility, for the wires AZ91 and AMX602 and AZX902, the increase is lower, due to the low drawing limit. When we observe the drawing limit of the drawn wires, aluminium content also noticeably decreases the maximum number of passes before breaking, especially in the cases of AZ31, AZ61 and AZ91, in the other wires cases, the trend still keeps true, even though it varies due to the other elements present in the wires. Zinc contents also has small relation to the mechanical properties, by increasing ductility with its increase, but the tensile strength of the material declines. Table 4. Tensile strength and breaking strain of drawn wires for every pass. Pass
1
2
3
4
5
6
TS[MPa]
ε
TS
ε
TS
ε
TS
ε
TS
ε
TS
ε
AZ31
336
0.062
376
0.042
403
0.041
408
0.02
401
0.018
381
0.017
AZ61
361
0.06
420
0.034
425
0.022
468
0.027
275
0.017
AZ91
370
0.028
427
0.02
327
0.017
AM60
352
0.047
403
0.031
411
0.029
413
0.021
296
0.014
AZX912
299
0.064
341
0.035
378
0.023
324
0.013
AMX602
366
0.037
370
0.027
373
0.022
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Vladimir Stefanov Hristov/ Procedia Manufacturing 00 (2018) 000–000 Vladimir Stefanov Hristov et al. / Procedia Manufacturing 15 (2018) 341–348
(a) Maximum Tensile Strength vs Al content AZ61 AZ31
400
0.07
AM60
AZ91
0.06
AMX602
350
0.05 0.04
300
200
0.03
Pure Mg
250 0
0.02 2
4 6 Al content in wires
8
10
Pure Mg
10
0.08
AZX912
0.01
Number of passes before break
450
(b) Drawing Limit vs Al content
0.09
Breaking Strain
Maximum Tensile Strength
500
64
8 AZ31
6
AZ61
AZX912 AM60
4 AMX602
31 24
2 0
45 39
AZ91
0
2
4 6 Al content in wires
8
10
Fig. 6. Relation between aluminium content and mechanical properties for drawn magnesium alloy wires: ■ Pure Mg, AZ31, AZ61, AZ91, ▲ AM60, ⅹ AZX912, ◊AMX602.
Furthermore, when following the tensile strength and elongation of the wires for every pass, there is a noticeable trend of increase of strength with a proportional decrease of the breaking strain of the materials. In Fig. 7, the trend can be seen, and also it is noticeable that towards the last passes of the drawing, the mechanical properties of the wires decline in both tensile strength and ductility. (a) AZ31
(b) 408
401
0.05
0.042
360
0.04
0.033 336
340
0.03 0.017
0.02
320 300
381
376
380
316 0
60
468
450
0.06
400
420
0.01
0.07
425
0.06
372
350
0.05
361
300
0.034
250
0.029
200 0.02
0.018 20 40 Total reduction [%]
0.08
500
0.06 Breaking strain
Tensile strength
400
AZ61
0.04
275
0.03
0.027 0.017
0.02 0.01
150 100
Breaking strain
403
0.062
0.07
Tensile strength
420
0
20 40 Total reduction[%]
60
0
Fig. 7. Tensile strength and breaking strain in every pass of the cold drawing process for AZ31 and AZ61.
2.4. Surface and cracks observation by microscope and SEM The decrease of ductility in the final passes of the magnesium alloy wires is a significant problem. That is why the surface area of the wires and was observed by SEM, the surface was also observed after polishing the wire and observing the closest area to the surface. As seen from the pictures in Fig. 8, the surface area seen from the inside of the wires has a significant number of cracks and defects. They appear due to the increase of hardness on the surface of the wires and the accumulation of shearing stress. That is why even though, the drawing limit of the wires is set between 3 and 6 passes, the last useable wire is at least one pass before the breaking point.
50µm Vladimir Stefanov HristovProcedia et al. / Procedia Manufacturing (2018) 341–348 Vladimir Stefanov Hristov/ Manufacturing 00 (2018)15000–000
AZ91
AM60
Crack
3477
Cracks
50µm
50µm
50µm Fig. 8. Surface cracks of drawn AZ91 and AM60 wires at 3rd pass.
After Scanning Electron Microscopy on the surfaces of the annealed mother wires and the drawn wires at 2.09 mm, the cold wire drawing seems to preserve the wire surface of the drawn wires. Mother wire
AZ31
Mother wire
AZ61
2.09mm
AM60
50µm
Mother wire
2.09mm
2.09mm
AZX912
500µm
Mother wire
AMX602 2.09mm
2.09mm
500µm
AZ91
500µm
500µm
Mother wire
Mother wire
2.09mm
500µm
500µm
Fig. 9. SEM images of drawn wire surface of magnesium alloy wires.
3.
Conclusion
After drawing six different magnesium alloy wires, by using cold wire drawing to their drawing limit and examining their mechanical properties, the following conclusions have been drawn:
Vladimir Stefanov Hristov et al. / Procedia Manufacturing 15 (2018) 341–348 Vladimir Stefanov Hristov/ Procedia Manufacturing 00 (2018) 000–000
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1) By using 10% reduction per pass, a tungsten carbide die with a die half-angle α=6⁰, it was possible to draw, six different magnesium alloy wires, from a starting diameter of 2.4 to a total reduction between 30-45% by cold wire drawing. 2) Testing the drawn wires, proved was possible to build a graph following the increase of tensile strength in comparison to decrease of ductility which can be used for each of the examined wires. 3) After comparing the results of the testing between the different wires, the aluminium content of the magnesium alloy wires proves vital to the mechanical properties of the drawn wires, a relation could be established between tensile strength, breaking strain, drawing limit and the chemical composition of the material. 4) Examining the increase of tensile strength in the drawn wires for every pass a reciprocal relation can be establish with the decrease of maximum breaking strain for the same pass, there is also a significant decrease in mechanical properties towards the finishing pass. 5) When observing the area surface of the wires with a microscope, appearance of cracks and defects can be confirmed, which leads to drop in mechanical properties close to the finishing pass, also SEM images show that despite this, the drawn magnesium alloy wires up to the 3rd pass retain surface similar to the annealed mother wire Acknowledgement We would like to express our gratitude to Nito Seiko Co. and Kinomoto Shinsen Co. in Japan, for providing the testing materials and proving helpful during the process of our work. References [1] K. Yoshida, K Doi, Improvement of ductility of aluminum drawn wire by alternate drawing, Interwire 2013, (2014) 77–79. [2] K. Yoshida, Cold drawing of magnesium alloy wire and fabrication of micro screws, Steel Grips 2 Suppl. Metal Forming, (2004) 199–201. [3] K. Lange, Drawing and Ironing, In Handbook of Metalforming, McGraw-Hill Book Company, New York, (1985) 14–27. [4] K. Yoshida, Basis of plastic working, Sangyo-Tosho Publishing, (1988) 66. [5] E. Ayman, K. Katsuyoshi, I. Hisashi, U. Junko, K. Masahi, Mechanical characteristics of hot extruded non-combustible magnesium alloy using water atomized powder, JWRI, 37 (2008) 2. [6] GondaMetal - http://gondametal.co.jp/product_mag/material_kenzai/pdf/flame_retardance.pdf