电脉冲辅助TA2钛合金管材气胀成形实验研究
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摘要
目的研究电脉冲周期对管材成形性能的影响。方法对成形温度进行热电耦合数值分析,寻找到合适的电脉冲参数。对TA2钛合金管材进行了电脉冲辅助气胀成形实验,研究电脉冲周期管材胀形率、形状误差系数、微观组织、显微硬度分布的影响,分析电脉冲辅助胀形过程中动态再结晶现象。结果随着电脉冲周期的增大,管材膨胀率增大,形状误差率减小。当电脉冲周期增大到30 s时,膨胀率达到最大值42.7%,形状误差率仅为0.259%;电脉冲作用下,管材温度曲线呈现出明显的锯齿状上升,电能转化的温升与计算结果相近;EBSD观察发现材料在较低的温度(600℃)下发生了动态再结晶现象,组织细化,塑性提高。结论随着电脉冲周期的增大,管材塑性提高,环向变形均匀性得到改善。低频电脉冲的引入使TA2钛合金再结晶温度降低,晶粒发生细化。
The paper aims to study influences of electric pulse period on forming performance of tube. Thermoelectric coupling values of forming temperature are analyzed to find out proper electropulsing parameters. The effects of expansion ratio, shape deviation ratio, microstructure and microhardness distribution of the forming tubes were analyzed through electropulsing-assisted gas forming experiment on TA2 titanium alloys. Dynamic recrystallization in the electropulsing-assisted gas forming was analyzed. The results showed that with the increase of the electric pulse period, the expansion ratio of the tube was enlarged, and the shape deviation ratio was decreased. When the period of electric pulse increased to 30 s, the expansion rate reached the highest value of 42.7% and the shape deviation ratio was only 0.259%. The temperature profile presented a serration shaped growth under the action of electric pulse. The temper ature rise was consistent with the calculation results. The electron backscattered diffraction(EBSD) results showed that obvious dynamic recrystallization occurred at a lower temperature(600 ℃). Meanwhile, the grains were refined and the plasticity was improved. The conclusion is that with the increase of the electric pulse period, the plasticity of the tube is improved, and the uniformity of the circumferential deformation is also improved. The temperature of dynamic recrystallization of TA2 titanium alloy is decreased and the grain is refined with the introduction of low frequency electropulsing.
The paper aims to study influences of electric pulse period on forming performance of tube. Thermoelectric coupling values of forming temperature are analyzed to find out proper electropulsing parameters. The effects of expansion ratio, shape deviation ratio, microstructure and microhardness distribution of the forming tubes were analyzed through electropulsing-assisted gas forming experiment on TA2 titanium alloys. Dynamic recrystallization in the electropulsing-assisted gas forming was analyzed. The results showed that with the increase of the electric pulse period, the expansion ratio of the tube was enlarged, and the shape deviation ratio was decreased. When the period of electric pulse increased to 30 s, the expansion rate reached the highest value of 42.7% and the shape deviation ratio was only 0.259%. The temperature profile presented a serration shaped growth under the action of electric pulse. The temper ature rise was consistent with the calculation results. The electron backscattered diffraction(EBSD) results showed that obvious dynamic recrystallization occurred at a lower temperature(600 ℃). Meanwhile, the grains were refined and the plasticity was improved. The conclusion is that with the increase of the electric pulse period, the plasticity of the tube is improved, and the uniformity of the circumferential deformation is also improved. The temperature of dynamic recrystallization of TA2 titanium alloy is decreased and the grain is refined with the introduction of low frequency electropulsing.
引文
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[3]苑世剑,刘伟,徐永超.板材液压成形技术与装备新进展[J].机械工程学报,2015,51(8):20-28.YUAN Shi-jian,LIU Wei,XU Yong-chao.New Development on Technology and Equipment of Sheet Hydroforming[J].Journal of Mechanical Engineering,2015,51(8):20-28.
[4]徐勇,张士宏,马彦,等.新型液压成形技术的研究进展[J].精密成形工程,2016,8(5):7-14.XU Yong,ZHANG Shi-hong,MA Yan,et al.Hydroforming Technology:State-of-the-arts and Recent Developments[J].Journal of Netshape Forming Engineering,2016,8(5):7-14.
[5]刘钢,武永,王建珑,等.钛合金管件高压气胀成形工艺研究进展[J].精密成形工程,2016,8(5):35-40.LIU Gang,WU Yong,WANG Jian-long,et al.Research Progress of High Pressure Gas Forming for Titanium Alloy Tubular Components[J].Journal of Netshape Forming Engineering,2016,8(5):35-40.
[6]LI C,ZHANG K F,JIANG S S,et al.Pulse Current Auxiliary Bulging and Deformation Mechanism of AZ31 Magnesium Alloy[J].Materials&Design,2012,34:170-178.
[7]HE Zhu-bin,FAN Xiao-bo,SHAO Fei,et al.Formability and Microstructure of AA6061 Al Alloy Tube for Hot Metal Gas Forming at Elevated Temperature[J].Transactions of Nonferrous Metals Society of China,2012,22(S2):364-369.
[8]MAENO T,MORI K,UNOU C.Improvement of Die Filling by Prevention of Temperature Drop in Gas Forming of Aluminium Alloy Tube Using Air Filled into Sealed Tube and Resistance Heating[J].Procedia Engineering,2014,81:2237-2242.
[9]MAENO T,MORI K,ADACHI K.Gas Forming of Ultra-high Strength Steel Hollow Part Using Air Filled into Sealed Tube and Resistance Heating[J].Journal ofMaterials Processing Technology,2014,214:97-105.
[10]MICHIELETTO F,GHIOTTI A,BRUSCHI S.Novel Experimental Set-Up to Test Tubes Formability at Elevated Temperatures[J].Key Engineering Materials,2014,611:62-69.
[11]ZHANG W,ZHAO W S,LI D X,et al.Martensitic Transformation from Alpha-Ti to Beta-Ti on Rapid Heating[J].Applied Physics Letters,2004,84(24):447-459.
[12]邓肯.钛的应用与选择[M].北京:冶金工业出版社,1988.DENG Ken.Application and Selection of Titanium Alloy[M].Beijing:Metallurgical Industry,1988.
[13]WANG K,LIU G,ZHAO J,et al.Formability and Microstructure Evolution for Hot Gas Forming of Laser-welded TA15 Titanium Alloy Tubes[J].Materials&Design,2016,91:269-277.
[14]BREWER L N,OTHON M A,YOUNG L M,et al.Misorientation Mapping for Visualization of Plastic Deformation via Electron Back-Scattered Diffraction[J].Microscopy and Microanalysis,2006,12(1):85-91.
[15]BELLAVOINE M,DUMONT M,DRILLET,et al.Influence of Microalloying Elements Ti and Nb on Recrystallization during Annealing of Advanced High-Strength Steels[C]//Materials Science Forum,2017.