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研究了铸态TC21钛合金在温度1000~1150℃,应变速率0.01~10s-1条件下的高温压缩变形行为,基于动态材料模型建立了热加工图,并结合变形微观组织观察确定了该合金在实验条件下的高温变形机制及加工工艺。结果表明:TC21合金在β相区进行热压缩,主要变形机理为动态回复;Ⅰ区(高应变速率,ε&≥1s-1),材料落入流动失稳区域,其微观变形机制为局部塑性流动,在制定热加工工艺时应尽量避免;Ⅱ区(1050~1120℃,0.1~1s-1),β晶粒变扁、拉长,晶界平直,为典型的动态回复,功率耗散率为32%~34%;最优加工区,Ⅲ区(低应变速率0.01~0.1s-1),功率耗散为38%~46%,拉长的β晶粒晶界上出现连续再结晶现象,首火次开坯应在高温(1150℃)附近进行,以提高铸态组织的塑性,随后开坯应在中低温进行,以得到细小均匀的β晶粒。
The high temperature compressive deformation behavior of as-cast TC21 titanium alloy at temperature of 1000-1150 ℃ and strain rate of 0.01-10 s-1 was studied. The hot working diagram was established based on the dynamic material model. Combined with the deformation microstructure observation, High Temperature Deformation Mechanism and Processing Technology under Experimental Conditions. The results show that the main deformation mechanism of TC21 alloy is dynamic compression in the β phase region. In the Ⅰ region (high strain rate, ε & ≥1s-1), the material falls into the area of flow instability and its microscopic deformation mechanism is local plastic flow , In the development of thermal processing technology should be avoided; Ⅱ area (1050 ~ 1120 ℃, 0.1 ~ 1s-1), β grains become flat, elongated, grain boundary straight, the typical dynamic response, power dissipation rate Is 32% ~ 34%. The best processing area, Ⅲ area (low strain rate 0.01 ~ 0.1s-1), the power dissipation is 38% ~ 46%, continuous recrystallization appears on the elongated β grain boundaries , The first opening of the blaze should be carried out at high temperature (1150 ℃) in order to improve the ductility of the as-cast microstructure, and then open the blanks should be carried out at low temperature to get fine and uniform β grains.