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Effect Of Warm Rolling On Microstructure, Porosity And Hardness Of Spray Formed LM25 Alloy
Available online at www.sciencedirect.com
ScienceDirect Materials Today: Proceedings 18 (2019) 3910–3915
www.materialstoday.com/proceedings
ICMPC-2019
Effect Of Warm Rolling On Microstructure, Porosity And Hardness Of Spray Formed LM25 Alloy B.V.R. Reddya, S.R. Maityb, K.M. Pandeyc a
Department of Mechanical Engineering, National Institute of Technology, Silchar, Assam, India-788010
Abstract
LM25 alloy was obtained by the consolidated spray forming method. By using power saw the central portion was cut down into 20mmX20mm and then warm rolled with 20%,40%, 60% and 80 % at 1000c.Samples were prepared as per standards to see the microstructure by using the optical microscope. The results show that fine microstructure was observed in LM25 spray deposited Al alloy after warm rolling process due to the expediting cooling and freezing rate of spray deposit. Porosity and Mechanical properties of the warm rolled LM 25 substrate was improved than the spray casted and cold rolled. © 2019 Published by Elsevier Ltd. Selection and peer-review under responsibility of the 9th International Conference of Materials Processing and Characterization, ICMPC-2019
Keywords: Spray forming; Warm rolling; Microstructure; Porosity; Hardness Introduction In electronic devices, video tape recorder cylinders, valve spring retainers, air conditioning compressor parts and shipping applications Al-Si is widely used because of their tremendous properties like stiffness, tribology, low weight to high strength [1], resist to corrosion, minimum thermal expansion and easily castable [2]. Spray forming is one of the prominent technique to produce aggregated preform in the single step to achieve grain refinement and homogeneous mixing of Al-Si alloy. Where as in case of other casting methods like Ingot method, rheocasting method, stir casting and powder metallurgy [3] etc.
* Corresponding author. E-mail address: [email protected] 2214-7853 © 2019 Published by Elsevier Ltd. Selection and peer-review under responsibility of the 9th International Conference of Materials Processing and Characterization, ICMPC-2019
B.V.R .Reddy et al./ Materials Today: Proceedings 18 (2019) 3910–3915
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The processing steps are more, not economical, chemically inhomogeneous and coarse grain structures obtained. Due to the above reasons spray casting method was opted in this paper. Spray droplets was fallen over the substrate with high atomization speed. Due to that more porosity was developed in all portions and exhibits poor mechanical properties [4]. So, it is required to prepare fully condense metal part with improved properties like hardness, strength etc. the pores must be nullified over surface of the subtract and distorted plastically. There are various methods to improve mechanical properties and to control porosity like warm rolling [5], cold rolling, extrusion, hot rolling and forging [6] etc. Rolling operation (two high rolling machine direction is opposite to the work piece) helps to remove and reduce the pores due to the unequal principal stresses developed during rolling. Therefore, it is an effective method to overcome porosity [7]. Wang Xiao et al [8] reported that effect of hot rolling on spray deposited AZ91 alloy. They found before hot rolling porosity was more i.e. 3%, later I was tremendously decreased to 0.5 percent. Subtract was hot rolled 2500c and reduced thickness at 20%, 40% 60% and 80% in single pass. It was observed the grain size smaller in 80% reduction because of dynamic recrystallization. Manas R. Tripathy et al [9] noticed during rolling good bonding was developed between the substrate and deposit. As the percentage of rolling increases the pores were eliminated and porosity decreased because of the rolling direction. 2. Experimental Procedure To analyse the Mechanical and Metallurgical properties of the various samples in the central Portion of spray deposit, it is required to produce the Al-%6Si substrate by using the spray forming technology. The schematic representation of the liquid to semi solid processing elsewhere [10]. In this paper Al and Si was taken in %Wt. by 94 and 6. The Al and Si crystals were taken into different graphite crucibles. Due to the temperature differences in the metals, it is required to melt the silicon contained graphite crucible initially in a resistance heating furnace. Silicon cubes was started to melt after 14500c, therefore it is required to add excess temperature (Superheated) about 2000c to convert cubes completely into the molten metal. When silicon contained crucible reached to a temperature about 7900c, it is required to add Al cubes into that crucible to complete the melting process. Now assemble induction furnace, graphite crucible, atomizer (which is connected to nitrogen filled compressor) and delivery tube to the centre of the convergent-divergent nozzle, maintain the distance between tip of tube and rotar is 410mm. Now lighten all the processing parameters [11] and instantly pour the molten metal through delivery tube and release the nitrogen gas through atomizer at a pressure about 10 bar, resulting semisolid droplets were fallen over the copper substrate and spray deposition was held. Sample of size 20mmx20mmx20mm are cut down from centre of the deposit and heat up to a fixed temperature 1000C, cool down in presence of air. Then roll the sample by using 2-high rolling machine for various passes as mentioned in the Table 1. Table 1. Warm Rolling conditions Iteration No.
Thickness of the sample Initially(mm)
Thickness of the sample Finally(mm)
% of thickness reduction
Warm rolling Temperature(0C)
1 2 3 4 5
20 20 16 10.50 4.2
20 16 10.50 4.2 0.84
0 20 40 60 80
100 100 100 100 100
Samples were cut down from every roll pass with size of 10mmx10mm to analyse the rolling direction and microstructure. Above samples initially gone through abrasive grinding (to remove unnecessary particles over the surface and edges) and mount these by using Bakelite as adhesive agent. Now the mounted samples were gone through the paper polishing with an emery paper of 1/0, 2/0, 3/0 and 4/0 specification, there after paper polished samples were undergone wheel cloth polishing (rotational speed of the wheel less than 250 rpm) using an emulsion powder of alumina suspended in H2O. After that samples were dry it with drier and etch it with Keller’s reagent (190ml of distilled water, 5ml of Nitric acid, 3ml of HCL and 2ml of HF). After completion of above steps systematically samples were examined with Leitz optical Microscope. To know the percentage of surface porosity
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B.V.R. Reddy et al./ Materials Today: Proceedings 18 (2019) 3910–3915
present in the warm rolled samples for various percentage thickness reductions 0%,20%,40%,60% and 80% from the centre of the deposit, these were examined under the image analysis using the optical microscope ‘Olympus model PM-3-311U’ in conjunction with a computer having image analysis software from ‘De-Winter materials plus’ To determine total porosity in the warm rolled samples for various thickness reductions, it is required to calculate measured density by using Archimedes principle and followed by the ASTM B328-96 practice and average the obtained values . It is required to know the presence of hardness in each sample for various warm rolled thickness reductions. It is required to calculate VHN for all samples by using Vickers test mode HPO 250 at 16kg load, by moving the indenter to various locations of the specimen and calculated average hardness value. 3. Results and discussion 3.1 Spray Deposit shape and Microstructural Analysis Shape of the spray deposit LM25 aluminium alloy with thickness 20mm and diameter 200mm was obtained at an angle of 00 and distance between top of delivery tube and rotor is about 400mm as shown in the figure.1
Figure 1. Shape of the LM25 spray deposit The deposit shape was depending upon on four factors like pouring time, atomizing gas, rotor angle and Appropriate spray cone has been obtained when pouring should be rapid, optimum atomizing gas pressure about 10bar. the inclination of the rotor is 00, mass of the semi solid droplets distribution was more uniform than the other angles. Microstructural pictographs of LM25 aluminium alloy before and after warm rolling was shown in the Fig.2. From Figure 2a. it was observed after spray forming and before warm rolling the LM25 aluminium alloy morphology is equally distributed Si phase into the aluminium metal matrix phase. Energy dispersive spectography analysis has been revealed the individual composition of the metal and colour identification. This analysis disclosed that is major portion is in bright color belongs to Al-Phase and Minor portion in grey contrast belongs to Si phase. Grain size of the phases calculated by using Hall-Petch equation [12], Al grain size is about 20-35µm and Si size is about 4-5µm. Before warm rolling pores obtained due to rapid solidification of molten liquid into semi solid droplets, pore size is about 12-14µm. warm rolled (for various thickness reductions) microstructures of LM25 aluminium alloy was represented in the fig.2b-e. By increasing the percentage of thickness reduction of the specimen’s grain boundaries were prolongated and average width of the Al grain size in Fig.2b, c. is 10-15µm and in Fig2d, e the length of Al grain is 15-20µm. It has been observed the grain length less in case of warm rolled samples than the cold rolled samples [6], because samples temperature increased and then air cooled. It was observed one more factor influencing the Mechanical properties is porosity. It has been observed many pores are formed over the surface of the spray deposit after deposition and before warm rolling over the copper plate. These pores are formed due to the liquid particles striking velocity is more and flow is incompressible, it is of one type of cast defect. Cast defected pores are reduced by the warm rolling for various thickness reductions and porosity was nullified for 80% thickness reduction but cracks are developed due to the rolling and leads to porosity this type of porosity named as crack porosity. From Fig2a, for %20 thickness reduction due to warm rolling the crack size was more, From Fig 2b it was observed that 20% rolled samples warm rolled up to 40 % the crack size was reduced more than earlier because of the restacking and rearrangement of the metals leads to removal of the porosity. it has been repeated up to 80 % reduction in thickness samples, the porosity was completely eliminated.
B.V.R .Reddy et al./ Materials Today: Proceedings 18 (2019) 3910–3915
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(A)
(B)
(D)
50μm
(C)
50μm
(E)
50μm
50μm
Figure.2 Microstructural Pictograph’s of spray formed LM25 aluminium alloy (a) before warm rolling, After warm rolling for various thickness reductions in central region (b) %20 (c) % 40 (d) %60 (e) %80.
3.2. Porosity Due to rolling and spray casting processes porosity was developed over the surface and inside the sample. Surface porosity has been observed and calculated with optical microscope and absolute porosity was determined by using Archimedes’ principle for LM25 Aluminium alloy. The main reason to develop the porosity in the sample is due to Nitrogen gas entrapment into the liquid molten metal, lagging melt to fill pores, difficulty in evaluation of dissolved gas and shrinkage during solidification. All these are explained in the literature [13,14]. In this paper porosity values have been compared between spray cast specimens, cold rolled samples and warm rolled samples. Among these warm rolled samples possesses less porosity in comparison due to heating and cooling of samples the grain size is less and all grains are compacted in systematic way. Porosity values have been plotted in the graph as shown in the Figure.3. As the percentage of reduction in the sample is increasing the pores are disappear due to overlapping. Upto 60% thickness reduction some porosity has observed after that the percentage of porosity is very less.
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Figure 3: Variation of porosity for various percentages of thickness warm rolled LM25 samples
Figure 4: Variation of Vickers Hardness Value for various percentages of thickness warm rolled LM25 samples 3.3. Hardness The Vickers hardness value of LM25 aluminium alloy has been calculated before and after warm rolling. Before rolling of (%0, %20, %40, %60, %80) the hardness values in the range of 50-90VHN as represented in the Figure 4. After warm rolling the Vickers hardness value increased in the range of 60-140VHN. As the thickness reduction increases in the samples the hardness value increased as represented in the Figure 4. It has been observed the hardness values of warm rolled samples are better than cold rolled and spray deposited samples because of sudden expansion and compaction in the samples. It has been observed that warm rolled samples having more hardness than the cold rolled and spray deposited samples.
B.V.R .Reddy et al./ Materials Today: Proceedings 18 (2019) 3910–3915
3915
Conclusions Appropriate shape of the spray deposit was obtained at 00 inclination angles of the rotar, distance between the end of the delivery tube to substrate distance was 410mm and controlled atomized pressure about 10 bar. 1.
The grain size of spray deposited alloy is 35-40µm, cold rolled samples average grain size is about 25-35 µm and warm rolled samples grain size is about 15-25 µm.
2.
Surface porosity of warm rolled samples are lower than spray deposited and cold rolled samples
3.
It has been observed porosity due to cracks and casting can be eliminated by warm rolling.
4.
Hardness values of warm rolled samples(60-140VHN) are more than casted(50-90VHN) and cold rolled(50120VHN) samples.
References 1) 2) 3) 4) 5) 6) 7) 8) 9) 10) 11) 12) 13) 14)
C.Cui, A. Schulz, K. Schimanski, H-W. Zoch, Journal of Material Processing Technology 209 (2009) 5220. K.V. Ojha, Aruna Tomar, Devendra Singh and G.C. Kaushal, Trans.Indian Inst.Met 61(2008) 139. P.S. Grant, Progress in Material Science 39 (1995) 497-545. Hari Prasad S, Sastry S M L, Jerian K L, and Lederich R J, Metall. Trans. 24 (1993) 865. R. Machado, A.H. Kasama, A.M. Jorge Jr., C.S. Kiminami, W.J. Batta Fo, C. Bolfarini Material Science and Engineering, A449-451 (2007) 854-857. Rashmi Mittal, Devendra Singh, Trans. Indian Inst. Met. 67(4) (2014) 551-557. Deshmukh A R, Sundararajan T, Dube R K, and Bhargava S, J Mater Process Technol 84 (1998) 56 WANG Xiao-feng, ZHAO Jiu-Zhou, HE Jie, HUZhuang-qi, Trans.Nonferrous Met.Soc. China 17 (2007) 238-243 Manas R. Tripathy, Ravindra K. Dube, Satish C. Coria, Journal of Materials Processing Technology 190 (2007) 342-349 Kamal Preet Kaur, O.P. Pandey, Journal of alloys and compounds 503 (2010) 410-415 Mathur, S. Annavarapu, D. Alpelian, A. Lawley, Mater.Sci. Eng., A142(1991) 261-276 Y.Z. Zhu, S.Z. Wang, B.L. Li, Z.M. Yin, Q. Wan, P. Liu, Materials and Design 55 (2014) 456-462 Sahu K.K, Dube R.K, Koria S.C, Powder Metall. 52 (2009) 135-144. 14. Muller HR, Ohlak, Zauter R, Ebner M, Mater Sci. Engg. A 383 (2004) 78-86
ScienceDirect Materials Today: Proceedings 18 (2019) 3910–3915
www.materialstoday.com/proceedings
ICMPC-2019
Effect Of Warm Rolling On Microstructure, Porosity And Hardness Of Spray Formed LM25 Alloy B.V.R. Reddya, S.R. Maityb, K.M. Pandeyc a
Department of Mechanical Engineering, National Institute of Technology, Silchar, Assam, India-788010
Abstract
LM25 alloy was obtained by the consolidated spray forming method. By using power saw the central portion was cut down into 20mmX20mm and then warm rolled with 20%,40%, 60% and 80 % at 1000c.Samples were prepared as per standards to see the microstructure by using the optical microscope. The results show that fine microstructure was observed in LM25 spray deposited Al alloy after warm rolling process due to the expediting cooling and freezing rate of spray deposit. Porosity and Mechanical properties of the warm rolled LM 25 substrate was improved than the spray casted and cold rolled. © 2019 Published by Elsevier Ltd. Selection and peer-review under responsibility of the 9th International Conference of Materials Processing and Characterization, ICMPC-2019
Keywords: Spray forming; Warm rolling; Microstructure; Porosity; Hardness Introduction In electronic devices, video tape recorder cylinders, valve spring retainers, air conditioning compressor parts and shipping applications Al-Si is widely used because of their tremendous properties like stiffness, tribology, low weight to high strength [1], resist to corrosion, minimum thermal expansion and easily castable [2]. Spray forming is one of the prominent technique to produce aggregated preform in the single step to achieve grain refinement and homogeneous mixing of Al-Si alloy. Where as in case of other casting methods like Ingot method, rheocasting method, stir casting and powder metallurgy [3] etc.
* Corresponding author. E-mail address: [email protected] 2214-7853 © 2019 Published by Elsevier Ltd. Selection and peer-review under responsibility of the 9th International Conference of Materials Processing and Characterization, ICMPC-2019
B.V.R .Reddy et al./ Materials Today: Proceedings 18 (2019) 3910–3915
3911
The processing steps are more, not economical, chemically inhomogeneous and coarse grain structures obtained. Due to the above reasons spray casting method was opted in this paper. Spray droplets was fallen over the substrate with high atomization speed. Due to that more porosity was developed in all portions and exhibits poor mechanical properties [4]. So, it is required to prepare fully condense metal part with improved properties like hardness, strength etc. the pores must be nullified over surface of the subtract and distorted plastically. There are various methods to improve mechanical properties and to control porosity like warm rolling [5], cold rolling, extrusion, hot rolling and forging [6] etc. Rolling operation (two high rolling machine direction is opposite to the work piece) helps to remove and reduce the pores due to the unequal principal stresses developed during rolling. Therefore, it is an effective method to overcome porosity [7]. Wang Xiao et al [8] reported that effect of hot rolling on spray deposited AZ91 alloy. They found before hot rolling porosity was more i.e. 3%, later I was tremendously decreased to 0.5 percent. Subtract was hot rolled 2500c and reduced thickness at 20%, 40% 60% and 80% in single pass. It was observed the grain size smaller in 80% reduction because of dynamic recrystallization. Manas R. Tripathy et al [9] noticed during rolling good bonding was developed between the substrate and deposit. As the percentage of rolling increases the pores were eliminated and porosity decreased because of the rolling direction. 2. Experimental Procedure To analyse the Mechanical and Metallurgical properties of the various samples in the central Portion of spray deposit, it is required to produce the Al-%6Si substrate by using the spray forming technology. The schematic representation of the liquid to semi solid processing elsewhere [10]. In this paper Al and Si was taken in %Wt. by 94 and 6. The Al and Si crystals were taken into different graphite crucibles. Due to the temperature differences in the metals, it is required to melt the silicon contained graphite crucible initially in a resistance heating furnace. Silicon cubes was started to melt after 14500c, therefore it is required to add excess temperature (Superheated) about 2000c to convert cubes completely into the molten metal. When silicon contained crucible reached to a temperature about 7900c, it is required to add Al cubes into that crucible to complete the melting process. Now assemble induction furnace, graphite crucible, atomizer (which is connected to nitrogen filled compressor) and delivery tube to the centre of the convergent-divergent nozzle, maintain the distance between tip of tube and rotar is 410mm. Now lighten all the processing parameters [11] and instantly pour the molten metal through delivery tube and release the nitrogen gas through atomizer at a pressure about 10 bar, resulting semisolid droplets were fallen over the copper substrate and spray deposition was held. Sample of size 20mmx20mmx20mm are cut down from centre of the deposit and heat up to a fixed temperature 1000C, cool down in presence of air. Then roll the sample by using 2-high rolling machine for various passes as mentioned in the Table 1. Table 1. Warm Rolling conditions Iteration No.
Thickness of the sample Initially(mm)
Thickness of the sample Finally(mm)
% of thickness reduction
Warm rolling Temperature(0C)
1 2 3 4 5
20 20 16 10.50 4.2
20 16 10.50 4.2 0.84
0 20 40 60 80
100 100 100 100 100
Samples were cut down from every roll pass with size of 10mmx10mm to analyse the rolling direction and microstructure. Above samples initially gone through abrasive grinding (to remove unnecessary particles over the surface and edges) and mount these by using Bakelite as adhesive agent. Now the mounted samples were gone through the paper polishing with an emery paper of 1/0, 2/0, 3/0 and 4/0 specification, there after paper polished samples were undergone wheel cloth polishing (rotational speed of the wheel less than 250 rpm) using an emulsion powder of alumina suspended in H2O. After that samples were dry it with drier and etch it with Keller’s reagent (190ml of distilled water, 5ml of Nitric acid, 3ml of HCL and 2ml of HF). After completion of above steps systematically samples were examined with Leitz optical Microscope. To know the percentage of surface porosity
3912
B.V.R. Reddy et al./ Materials Today: Proceedings 18 (2019) 3910–3915
present in the warm rolled samples for various percentage thickness reductions 0%,20%,40%,60% and 80% from the centre of the deposit, these were examined under the image analysis using the optical microscope ‘Olympus model PM-3-311U’ in conjunction with a computer having image analysis software from ‘De-Winter materials plus’ To determine total porosity in the warm rolled samples for various thickness reductions, it is required to calculate measured density by using Archimedes principle and followed by the ASTM B328-96 practice and average the obtained values . It is required to know the presence of hardness in each sample for various warm rolled thickness reductions. It is required to calculate VHN for all samples by using Vickers test mode HPO 250 at 16kg load, by moving the indenter to various locations of the specimen and calculated average hardness value. 3. Results and discussion 3.1 Spray Deposit shape and Microstructural Analysis Shape of the spray deposit LM25 aluminium alloy with thickness 20mm and diameter 200mm was obtained at an angle of 00 and distance between top of delivery tube and rotor is about 400mm as shown in the figure.1
Figure 1. Shape of the LM25 spray deposit The deposit shape was depending upon on four factors like pouring time, atomizing gas, rotor angle and Appropriate spray cone has been obtained when pouring should be rapid, optimum atomizing gas pressure about 10bar. the inclination of the rotor is 00, mass of the semi solid droplets distribution was more uniform than the other angles. Microstructural pictographs of LM25 aluminium alloy before and after warm rolling was shown in the Fig.2. From Figure 2a. it was observed after spray forming and before warm rolling the LM25 aluminium alloy morphology is equally distributed Si phase into the aluminium metal matrix phase. Energy dispersive spectography analysis has been revealed the individual composition of the metal and colour identification. This analysis disclosed that is major portion is in bright color belongs to Al-Phase and Minor portion in grey contrast belongs to Si phase. Grain size of the phases calculated by using Hall-Petch equation [12], Al grain size is about 20-35µm and Si size is about 4-5µm. Before warm rolling pores obtained due to rapid solidification of molten liquid into semi solid droplets, pore size is about 12-14µm. warm rolled (for various thickness reductions) microstructures of LM25 aluminium alloy was represented in the fig.2b-e. By increasing the percentage of thickness reduction of the specimen’s grain boundaries were prolongated and average width of the Al grain size in Fig.2b, c. is 10-15µm and in Fig2d, e the length of Al grain is 15-20µm. It has been observed the grain length less in case of warm rolled samples than the cold rolled samples [6], because samples temperature increased and then air cooled. It was observed one more factor influencing the Mechanical properties is porosity. It has been observed many pores are formed over the surface of the spray deposit after deposition and before warm rolling over the copper plate. These pores are formed due to the liquid particles striking velocity is more and flow is incompressible, it is of one type of cast defect. Cast defected pores are reduced by the warm rolling for various thickness reductions and porosity was nullified for 80% thickness reduction but cracks are developed due to the rolling and leads to porosity this type of porosity named as crack porosity. From Fig2a, for %20 thickness reduction due to warm rolling the crack size was more, From Fig 2b it was observed that 20% rolled samples warm rolled up to 40 % the crack size was reduced more than earlier because of the restacking and rearrangement of the metals leads to removal of the porosity. it has been repeated up to 80 % reduction in thickness samples, the porosity was completely eliminated.
B.V.R .Reddy et al./ Materials Today: Proceedings 18 (2019) 3910–3915
3913
(A)
(B)
(D)
50μm
(C)
50μm
(E)
50μm
50μm
Figure.2 Microstructural Pictograph’s of spray formed LM25 aluminium alloy (a) before warm rolling, After warm rolling for various thickness reductions in central region (b) %20 (c) % 40 (d) %60 (e) %80.
3.2. Porosity Due to rolling and spray casting processes porosity was developed over the surface and inside the sample. Surface porosity has been observed and calculated with optical microscope and absolute porosity was determined by using Archimedes’ principle for LM25 Aluminium alloy. The main reason to develop the porosity in the sample is due to Nitrogen gas entrapment into the liquid molten metal, lagging melt to fill pores, difficulty in evaluation of dissolved gas and shrinkage during solidification. All these are explained in the literature [13,14]. In this paper porosity values have been compared between spray cast specimens, cold rolled samples and warm rolled samples. Among these warm rolled samples possesses less porosity in comparison due to heating and cooling of samples the grain size is less and all grains are compacted in systematic way. Porosity values have been plotted in the graph as shown in the Figure.3. As the percentage of reduction in the sample is increasing the pores are disappear due to overlapping. Upto 60% thickness reduction some porosity has observed after that the percentage of porosity is very less.
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Figure 3: Variation of porosity for various percentages of thickness warm rolled LM25 samples
Figure 4: Variation of Vickers Hardness Value for various percentages of thickness warm rolled LM25 samples 3.3. Hardness The Vickers hardness value of LM25 aluminium alloy has been calculated before and after warm rolling. Before rolling of (%0, %20, %40, %60, %80) the hardness values in the range of 50-90VHN as represented in the Figure 4. After warm rolling the Vickers hardness value increased in the range of 60-140VHN. As the thickness reduction increases in the samples the hardness value increased as represented in the Figure 4. It has been observed the hardness values of warm rolled samples are better than cold rolled and spray deposited samples because of sudden expansion and compaction in the samples. It has been observed that warm rolled samples having more hardness than the cold rolled and spray deposited samples.
B.V.R .Reddy et al./ Materials Today: Proceedings 18 (2019) 3910–3915
3915
Conclusions Appropriate shape of the spray deposit was obtained at 00 inclination angles of the rotar, distance between the end of the delivery tube to substrate distance was 410mm and controlled atomized pressure about 10 bar. 1.
The grain size of spray deposited alloy is 35-40µm, cold rolled samples average grain size is about 25-35 µm and warm rolled samples grain size is about 15-25 µm.
2.
Surface porosity of warm rolled samples are lower than spray deposited and cold rolled samples
3.
It has been observed porosity due to cracks and casting can be eliminated by warm rolling.
4.
Hardness values of warm rolled samples(60-140VHN) are more than casted(50-90VHN) and cold rolled(50120VHN) samples.
References 1) 2) 3) 4) 5) 6) 7) 8) 9) 10) 11) 12) 13) 14)
C.Cui, A. Schulz, K. Schimanski, H-W. Zoch, Journal of Material Processing Technology 209 (2009) 5220. K.V. Ojha, Aruna Tomar, Devendra Singh and G.C. Kaushal, Trans.Indian Inst.Met 61(2008) 139. P.S. Grant, Progress in Material Science 39 (1995) 497-545. Hari Prasad S, Sastry S M L, Jerian K L, and Lederich R J, Metall. Trans. 24 (1993) 865. R. Machado, A.H. Kasama, A.M. Jorge Jr., C.S. Kiminami, W.J. Batta Fo, C. Bolfarini Material Science and Engineering, A449-451 (2007) 854-857. Rashmi Mittal, Devendra Singh, Trans. Indian Inst. Met. 67(4) (2014) 551-557. Deshmukh A R, Sundararajan T, Dube R K, and Bhargava S, J Mater Process Technol 84 (1998) 56 WANG Xiao-feng, ZHAO Jiu-Zhou, HE Jie, HUZhuang-qi, Trans.Nonferrous Met.Soc. China 17 (2007) 238-243 Manas R. Tripathy, Ravindra K. Dube, Satish C. Coria, Journal of Materials Processing Technology 190 (2007) 342-349 Kamal Preet Kaur, O.P. Pandey, Journal of alloys and compounds 503 (2010) 410-415 Mathur, S. Annavarapu, D. Alpelian, A. Lawley, Mater.Sci. Eng., A142(1991) 261-276 Y.Z. Zhu, S.Z. Wang, B.L. Li, Z.M. Yin, Q. Wan, P. Liu, Materials and Design 55 (2014) 456-462 Sahu K.K, Dube R.K, Koria S.C, Powder Metall. 52 (2009) 135-144. 14. Muller HR, Ohlak, Zauter R, Ebner M, Mater Sci. Engg. A 383 (2004) 78-86