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An Experimental study: Mechanical properties of Cu-Cr-Zr alloy
Available online at www.sciencedirect.com
ScienceDirect Materials Today: Proceedings 4 (2017) 301–306
www.materialstoday.com/proceedings
5th International Conference of Materials Processing and Characterization (ICMPC 2016)
An Experimental study: Mechanical properties of Cu-Cr-Zr alloy K.Viswanath Allamrajua *Korimilli Surya Sundara Raob Mechanical Engineering Department,National Institute of Technology, Warangal, India-506004
Abstract This paper presents, the hardness of a material varies depending on the composition of material, and how it is treated when processed. Here observed the changes in hardness of Cu-Cr-Zr (CRZ) alloy resulting from different process types, along with the accompanying changes in microstructure. Tests are carried out to study in detail of the Thermo-Mechanical Processing such as Cold Rolling, Hot Rolling and Tensile test on CRZ. In this paper, the hot rolling operation and cold rolling operation has been performed on small slabs of CRZ alloy. And then for prepared alloy that is hot and cold rolled alloys the microstructure has been evaluated. The hardness of these alloys is also evaluated. So based on the observations are found for each alloy a comparison study has been done. And arrived at the conclusions for each alloy that by cold working the Strength increases and ductility decreases and by hot working the strength decreases and ductility increases. And for the Tensile Test for the Solution treated samples of CRZ alloy found high strength and less ductility in comparison to the room temperature samples. The role of recrystalization on these alloys has also been explained. ©2017 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of Conference Committee Members of 5th International Conference of Materials Processing and Characterization (ICMPC 2016). Keywords:CRZ; Thermo-mechanical ; Cold rolling; Hot rolling;
1.INTRODUCTION The invention of CRZ alloy is a major breakthrough which has resolved many of the practical problems related to overheating, high temperature electrical conductivity applications and many others. The alloys of this invention improved properties and characteristics particularly with respect to the combination of super resistance to softening at elevated temperature and the high electrical conductivity. The presence of Zirconium has also enhanced the cold
* Corresponding author. Tel.: +91-9492060340; E-mail address:[email protected] 2214-7853©2017 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of Conference Committee Members of 5th International Conference of Materials Processing and Characterization (ICMPC 2016).
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K.Viswanath Allamraju/ Materials Today: Proceedings 4 (2017) 301–306
and hot working of this alloy. With progressively increasing need of higher temperatures in the aircraft industry this alloy has been preferred over the Silver-bearing copper alloy. Copper alloy such as copper chromium zirconium (CuCrZr) was extensively used as a structural material for the heat sink of TORE SUPRA (TS) components: toroidal pumped limiter (TPL), antenna protection, guard limiters (bumper) and endoscopy systems[1]. Many investigations on hardened copper has been discovered during the welding of this material [2]. Recrystalization is a process by which deformed grains are replaced by a new set of un deformed grains that nucleate and grow until the original grains have been entirely consumed. Recrystalization is usually accompanied by a reduction in the strength and hardness of a material and a simultaneous increase in the ductility. Note that the movable roller (ie. Upper Roller) is moved with the help of Balland Screw mechanism, fig 1.
Fig.1. Rolling machine
2.Experimental procedures 2.1 Cold Rolling of CRZ alloy The composition of CRZ alloy isChromium: 0.6-0.8%, Zirconium: 0.7-0.15% and Copper: Rest. The CRZ sample dimensions are initialthickness(T2)=26 mm, Length: 110 mmBreadth: 40 mm.The aim of this test isto obtain 20% reduction in the CRZ slab piece given in the table.1. Before cold rolling, the thickness of CRZ alloy is the initial thickness of 26 mm, after 20 passes the reduction of thickness is 1.7 mm, after 45 passes the reduction of thickness from initial is 3.5 mm and after 70 passes the reduction of thickness from initial is 5 mm. To obtain 20 % reduction of slab thickness the number of passes the material went through is 70 passes. Table.1 S.NO
No of Passes
Thickness(mm)
1
Before rolling
26 mm
2
After 20 passes
24.3 mm
3
After 45 passes
22.5 mm
4
After 70 passes
21 mm
2.2 Hot Rolling treatment of CRZ alloy The main aim isto obtain 20% reduction in the CRZ slab piece given in table 2.Before hot rolling, the thickness of CRZ alloy is the initial thickness of 26 mm, after 2 passes the reduction of thickness is 1.4 mm, after 4 passes the reduction of thickness from initial is 3.5 mm and after 8 passes the reduction of thickness from initial is 5 mm. To obtain 20 % reduction of slab thickness the number of passes the material went through is 8 passes.
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Table.2 S.NO
No of Passes
Thickness(mm)
1
Before rolling
26 mm
2
After 2 passes
24.6 mm
3
After 4 passes
22.5 mm
4
After 8 passes
21 mm
2.3Tensile test of CRZ solution treated samples The specification of the UTM is 300 KN. The Principle: A universal testing machine (UTM), also known as a universal tester, materials testing machine or materials test frame, is used to test the tensile strength and compressive strength of materials.Some examples of the standards that are to be followed for the UTM:ASTM E4 - Practices for Force Verification of Testing Machines and ASTM E74 - Practice for Calibration of Force Measuring Instruments for Verifying the Force Indication of Testing Machines. In this paper the Tensile test is carried out based on E8 ASTM standards, fig 2:
Fig.2. Specimen of CRZ alloy under tensile test
The strength and ductility parameters of the CRZ material by tensile testing is determined here and compared the properties of specimen at room temperature and the one done at 6000 c. The cross head velocity of UTM is 200 mm/min and the maximum load of 25 ton can be applied. 2.3.1Solution Treatment Solution treatment is the heating of an alloy to a suitable temperature, holding it at that temperature long enough to cause one or more constituents to enter into a solid solution and then cooling it rapidly enough to hold these constituents in solution.The CRZ specimens are solution treated i.e quenched in water after holding in the furnace at 950 centigrade.Test procedure:Thesolution treated specimens is held fixed between two head jaws.The load is given and specimen necking at ultimate tensile load and finally leads to failure. Simultaneously the loading and elongation is recorded as the Universal Testing Machine is interfaced with computer. It takes the data and simulates the stress – strain curve. The strength and ductility parameters are readily displayed with the help of software. The same above steps are repeated for the tensile test at a temperature of 6000c.
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2.3.2 Hardness testing of CRZ alloy Vickers hardness test is conducted on CRZ alloy. One test is on the received samples of CRZ alloy, another one is on cold rolled CRZ alloy and the third test is on hot rolled CRZ alloy. Table. 3(Reading 1: As received samples) Load
D1
D2
Hardness
5Kg
290
289.1
121
5Kg
285
289
120
5Kg
290
278
126
Load 5Kg 5Kg 5Kg
D1 239.7 256 267
D2 243.2 276 258
Hardness 191 190 189
D1 208 221 245
D2 204 216 231
Hardness 99 99.4 99.8
Table.4(Reading 2: Cold rolling)
Table. 5(Reading 3: Hot rolling) Load 5Kg 5Kg 5Kg
By observing the readings of tables 3,4 and 5 ,the hardness values of cold rolling increases and that of hot rolling decreases, this is due to Recrystalization phenomenon. 3. Results and discussion
Fig.3 Stress strain curve of CRZ alloy ( at room temperature and 600 deg C
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The shape of the CRZ alloy is circular cross section, room temperature CRZ alloy (1TRT L-1) and high temperature CRZ alloy (600 HT-L1), the yield stresses recorded are 52.5 N/mm2 and 176 N/mm2 . Maximum stresses are recorded from stress strain curve from figure3 above are 260 and 175 N/mm2. Figure 4 and 5 shows the optical microscope images of before and after cold rolling treatment. From figure 3 the observations are that the tensile properties depend on temperature. Yield strength, tensile strength, and modulus of elasticity decrease at higher temperatures, whereas ductility commonly increases. A materials fabricator may wish to deform a material at a high temperature (hot working) to take advantage of the higher ductility and lower required stress. (a)
(b)
(c)
Fig.4. CRZ samples optical microscope images before cold rolling treatment (a) at 100 µm (b) at 50 µm (c) at 20 µm
(a)
(b)
(c)
Fig. 5. CRZ alloy after cold treatment (a) at 100 µm (b) at 50 µm (c) at 20 µm
After conducting the Vickers Hardness test, the hardness value for samples of CRZ alloy is 121, for cold rolled CRZ alloy is 192 and for hot rolled CRZ alloy is 99.The value of Hardness for cold rolled is more than ‘As received’ samples because the grains are elongated and as a result the Strength increases and Ductility decreases.The value of hardness for hot rolled is less than the cold rolled because of recrystalization that is new grains are formed and thus its strength decreases and ductility increases. Figures 6 and 7 describes the grain structure after the cold rolling treatment and hot rolling treatment of CRZ alloys.The grain size is high in case of cold worked samples which is due to the elongation of grains.The grains are uniform in nature in the hot worked samples due to the formation of complete new grains hence improving the ductility.
Fig.6. Microstructure of Cold rolled CRZ alloy
K.Viswanath Allamraju/ Materials Today: Proceedings 4 (2017) 301–306
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4.Conclusion
Fig.7. Microstructure of hot rolled CRZ alloy
The mechanical properties of CRZ alloy such as ductility and hardness are studied before cold rolling, after cold rolling and hot rolling. Explained the significance of cold rolling through experimentation in brief. Cold rolling increases the strength of CRZ alloy but ductility is high in the case of hot rolling process of CRZ alloy. References [1] [2]
A. Durocher , M. Lipa , Ph. Chappuis , J. Schlosser ,T. Huber , B. Schedler , TORE SUPRA experience of copper chromiumzirconium electron beam welding, Journal of Nuclear Materials 307–311 (2002) 1554–1557. M. Lipa, in: Proceedings of the 20th Symposium On Fusion Technology, Marseille, France, 7–1 September 1998.
ScienceDirect Materials Today: Proceedings 4 (2017) 301–306
www.materialstoday.com/proceedings
5th International Conference of Materials Processing and Characterization (ICMPC 2016)
An Experimental study: Mechanical properties of Cu-Cr-Zr alloy K.Viswanath Allamrajua *Korimilli Surya Sundara Raob Mechanical Engineering Department,National Institute of Technology, Warangal, India-506004
Abstract This paper presents, the hardness of a material varies depending on the composition of material, and how it is treated when processed. Here observed the changes in hardness of Cu-Cr-Zr (CRZ) alloy resulting from different process types, along with the accompanying changes in microstructure. Tests are carried out to study in detail of the Thermo-Mechanical Processing such as Cold Rolling, Hot Rolling and Tensile test on CRZ. In this paper, the hot rolling operation and cold rolling operation has been performed on small slabs of CRZ alloy. And then for prepared alloy that is hot and cold rolled alloys the microstructure has been evaluated. The hardness of these alloys is also evaluated. So based on the observations are found for each alloy a comparison study has been done. And arrived at the conclusions for each alloy that by cold working the Strength increases and ductility decreases and by hot working the strength decreases and ductility increases. And for the Tensile Test for the Solution treated samples of CRZ alloy found high strength and less ductility in comparison to the room temperature samples. The role of recrystalization on these alloys has also been explained. ©2017 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of Conference Committee Members of 5th International Conference of Materials Processing and Characterization (ICMPC 2016). Keywords:CRZ; Thermo-mechanical ; Cold rolling; Hot rolling;
1.INTRODUCTION The invention of CRZ alloy is a major breakthrough which has resolved many of the practical problems related to overheating, high temperature electrical conductivity applications and many others. The alloys of this invention improved properties and characteristics particularly with respect to the combination of super resistance to softening at elevated temperature and the high electrical conductivity. The presence of Zirconium has also enhanced the cold
* Corresponding author. Tel.: +91-9492060340; E-mail address:[email protected] 2214-7853©2017 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of Conference Committee Members of 5th International Conference of Materials Processing and Characterization (ICMPC 2016).
302
K.Viswanath Allamraju/ Materials Today: Proceedings 4 (2017) 301–306
and hot working of this alloy. With progressively increasing need of higher temperatures in the aircraft industry this alloy has been preferred over the Silver-bearing copper alloy. Copper alloy such as copper chromium zirconium (CuCrZr) was extensively used as a structural material for the heat sink of TORE SUPRA (TS) components: toroidal pumped limiter (TPL), antenna protection, guard limiters (bumper) and endoscopy systems[1]. Many investigations on hardened copper has been discovered during the welding of this material [2]. Recrystalization is a process by which deformed grains are replaced by a new set of un deformed grains that nucleate and grow until the original grains have been entirely consumed. Recrystalization is usually accompanied by a reduction in the strength and hardness of a material and a simultaneous increase in the ductility. Note that the movable roller (ie. Upper Roller) is moved with the help of Balland Screw mechanism, fig 1.
Fig.1. Rolling machine
2.Experimental procedures 2.1 Cold Rolling of CRZ alloy The composition of CRZ alloy isChromium: 0.6-0.8%, Zirconium: 0.7-0.15% and Copper: Rest. The CRZ sample dimensions are initialthickness(T2)=26 mm, Length: 110 mmBreadth: 40 mm.The aim of this test isto obtain 20% reduction in the CRZ slab piece given in the table.1. Before cold rolling, the thickness of CRZ alloy is the initial thickness of 26 mm, after 20 passes the reduction of thickness is 1.7 mm, after 45 passes the reduction of thickness from initial is 3.5 mm and after 70 passes the reduction of thickness from initial is 5 mm. To obtain 20 % reduction of slab thickness the number of passes the material went through is 70 passes. Table.1 S.NO
No of Passes
Thickness(mm)
1
Before rolling
26 mm
2
After 20 passes
24.3 mm
3
After 45 passes
22.5 mm
4
After 70 passes
21 mm
2.2 Hot Rolling treatment of CRZ alloy The main aim isto obtain 20% reduction in the CRZ slab piece given in table 2.Before hot rolling, the thickness of CRZ alloy is the initial thickness of 26 mm, after 2 passes the reduction of thickness is 1.4 mm, after 4 passes the reduction of thickness from initial is 3.5 mm and after 8 passes the reduction of thickness from initial is 5 mm. To obtain 20 % reduction of slab thickness the number of passes the material went through is 8 passes.
K.Viswanath Allamraju/ Materials Today: Proceedings 4 (2017) 301–306
303
Table.2 S.NO
No of Passes
Thickness(mm)
1
Before rolling
26 mm
2
After 2 passes
24.6 mm
3
After 4 passes
22.5 mm
4
After 8 passes
21 mm
2.3Tensile test of CRZ solution treated samples The specification of the UTM is 300 KN. The Principle: A universal testing machine (UTM), also known as a universal tester, materials testing machine or materials test frame, is used to test the tensile strength and compressive strength of materials.Some examples of the standards that are to be followed for the UTM:ASTM E4 - Practices for Force Verification of Testing Machines and ASTM E74 - Practice for Calibration of Force Measuring Instruments for Verifying the Force Indication of Testing Machines. In this paper the Tensile test is carried out based on E8 ASTM standards, fig 2:
Fig.2. Specimen of CRZ alloy under tensile test
The strength and ductility parameters of the CRZ material by tensile testing is determined here and compared the properties of specimen at room temperature and the one done at 6000 c. The cross head velocity of UTM is 200 mm/min and the maximum load of 25 ton can be applied. 2.3.1Solution Treatment Solution treatment is the heating of an alloy to a suitable temperature, holding it at that temperature long enough to cause one or more constituents to enter into a solid solution and then cooling it rapidly enough to hold these constituents in solution.The CRZ specimens are solution treated i.e quenched in water after holding in the furnace at 950 centigrade.Test procedure:Thesolution treated specimens is held fixed between two head jaws.The load is given and specimen necking at ultimate tensile load and finally leads to failure. Simultaneously the loading and elongation is recorded as the Universal Testing Machine is interfaced with computer. It takes the data and simulates the stress – strain curve. The strength and ductility parameters are readily displayed with the help of software. The same above steps are repeated for the tensile test at a temperature of 6000c.
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K.Viswanath Allamraju/ Materials Today: Proceedings 4 (2017) 301–306
2.3.2 Hardness testing of CRZ alloy Vickers hardness test is conducted on CRZ alloy. One test is on the received samples of CRZ alloy, another one is on cold rolled CRZ alloy and the third test is on hot rolled CRZ alloy. Table. 3(Reading 1: As received samples) Load
D1
D2
Hardness
5Kg
290
289.1
121
5Kg
285
289
120
5Kg
290
278
126
Load 5Kg 5Kg 5Kg
D1 239.7 256 267
D2 243.2 276 258
Hardness 191 190 189
D1 208 221 245
D2 204 216 231
Hardness 99 99.4 99.8
Table.4(Reading 2: Cold rolling)
Table. 5(Reading 3: Hot rolling) Load 5Kg 5Kg 5Kg
By observing the readings of tables 3,4 and 5 ,the hardness values of cold rolling increases and that of hot rolling decreases, this is due to Recrystalization phenomenon. 3. Results and discussion
Fig.3 Stress strain curve of CRZ alloy ( at room temperature and 600 deg C
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The shape of the CRZ alloy is circular cross section, room temperature CRZ alloy (1TRT L-1) and high temperature CRZ alloy (600 HT-L1), the yield stresses recorded are 52.5 N/mm2 and 176 N/mm2 . Maximum stresses are recorded from stress strain curve from figure3 above are 260 and 175 N/mm2. Figure 4 and 5 shows the optical microscope images of before and after cold rolling treatment. From figure 3 the observations are that the tensile properties depend on temperature. Yield strength, tensile strength, and modulus of elasticity decrease at higher temperatures, whereas ductility commonly increases. A materials fabricator may wish to deform a material at a high temperature (hot working) to take advantage of the higher ductility and lower required stress. (a)
(b)
(c)
Fig.4. CRZ samples optical microscope images before cold rolling treatment (a) at 100 µm (b) at 50 µm (c) at 20 µm
(a)
(b)
(c)
Fig. 5. CRZ alloy after cold treatment (a) at 100 µm (b) at 50 µm (c) at 20 µm
After conducting the Vickers Hardness test, the hardness value for samples of CRZ alloy is 121, for cold rolled CRZ alloy is 192 and for hot rolled CRZ alloy is 99.The value of Hardness for cold rolled is more than ‘As received’ samples because the grains are elongated and as a result the Strength increases and Ductility decreases.The value of hardness for hot rolled is less than the cold rolled because of recrystalization that is new grains are formed and thus its strength decreases and ductility increases. Figures 6 and 7 describes the grain structure after the cold rolling treatment and hot rolling treatment of CRZ alloys.The grain size is high in case of cold worked samples which is due to the elongation of grains.The grains are uniform in nature in the hot worked samples due to the formation of complete new grains hence improving the ductility.
Fig.6. Microstructure of Cold rolled CRZ alloy
K.Viswanath Allamraju/ Materials Today: Proceedings 4 (2017) 301–306
306
4.Conclusion
Fig.7. Microstructure of hot rolled CRZ alloy
The mechanical properties of CRZ alloy such as ductility and hardness are studied before cold rolling, after cold rolling and hot rolling. Explained the significance of cold rolling through experimentation in brief. Cold rolling increases the strength of CRZ alloy but ductility is high in the case of hot rolling process of CRZ alloy. References [1] [2]
A. Durocher , M. Lipa , Ph. Chappuis , J. Schlosser ,T. Huber , B. Schedler , TORE SUPRA experience of copper chromiumzirconium electron beam welding, Journal of Nuclear Materials 307–311 (2002) 1554–1557. M. Lipa, in: Proceedings of the 20th Symposium On Fusion Technology, Marseille, France, 7–1 September 1998.