Research On The Semi-solid Deformation Of The Ti-7Cu Alloy

Titanium alloy plays an important role in many fields according to its special characteristics. Such as: aerospace,energy,petroleum and biomedical field. The highly cost price and the difficulty of processing technology lead to the price of titanium alloy production maintaining a high price.The semisolid processing technology had developed rapidly in Al, Mg alloy and steel since 1970.Nobody else involved Ti-Cu alloy except seminar who researched the semisolid deformation behavior and mechanical property of Ti14 and Ti230 alloy.Therefore, the semisolid processing technology of Ti-Cu alloy can provided theory and foundation for semisolid processing technology of titanium alloy.This article researched the semisolid deformation behavior of Ti-7Cu alloy at different deformation parameters using thermal simulation tester(Gleeble3500).The deformation temperatures contain 1223 K,1273K,1373 K and 1473 K.The deformation rates contain 0.005s-1,0.05s-1,0.5s-1and5s-1.The deformation reductions all are 50%.The semisolid deformation behavior of Ti-7Cu alloy has been analyzed by the stress-strain curves. The constitutive equation has been established from 1223 K to 1473 K. The deformation activation energy at different technological parameters has been calculated. The results discussed the deformation mechanism of Ti-7Cu alloy. Ultimately the article definited the safe processing regionalities and unsafe processing regionalities using the processing maps.The results of semisolid deformation of Ti-7Cu alloy showed many results as follows: The flow stress is sensitive to deformation temperature and deformation rate during semisolid deformation. The flow stress decreased with the increasing of temperature and the decreasing of strain rate. Simultaneously, the flow stress increased with the decreasing of temperature and the increasing of strain rate. The amplitude of flow stress is largest from 0.5s-1 to 5s-1.the constitutive equation established from 1223 K to 1473 K comply to Arrhenius hyperbolic sine relationship preferablely. The deformation activation energy was determined by temperature and flow stress. The grain boundaries precipitate liquid phase when the temperature above 1273 K, The deformation mechanism transformed from plastic deformation of solid particles to sliding between solid particles or flow of liquid incorporating solid particles. The deformation mechanism changed from 1323 K to 1373 K. Of course, every deformation mechanism occupied different proportions at different deformation parameters. The temperature from 1543 K to 1598 K and strain rate from 0.0025s-1 to 10s-1 consist to which produced dynamic recrystallization, which belongs to safe processing regionality. Unsafe processing regionalaties constituted by temperature from 1498 K to 1583 K and higher strain rate from 10s-1 to 100s-1. Processing regionalities constituted by temperature from 1473 K to 1543 K and strain rate from 3×10-5s-1 to 10-3s-1 and higher temperature from 1643 K to 1773 K, strain rate from 3×10-5s-1 to 3×10-4s-1 which occurred crackles easily.