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为了研究用于外科植入生物材料Ti-6Al-7Nb合金的热变形行为,利用Gleeble 2000热模拟实验机对Ti-6Al-7Nb合金在750～900℃温度范围和0.001～10.000 s-1应变速率范围内进行等温热压缩实验,试验在氩气保护下进行,采用金相显微镜和透射电镜观察热变形后的组织;通过计算变形激活能分析Ti-6Al-7Nb合金在热压缩过程中的变形机制。结果表明:流变应力在经历加工硬化阶段后均表现出流变软化现象,在较低应变速率ε=0.001～0.100 s-1时,材料的软化主要受α相动态再结晶影响;而在较高应变速率ε=1～10 s-1时,材料基本不发生再结晶,其软化是由于钛合金在变形过程中的绝热效应造成的。通过Arrhenius方程计算出合金在750,800,850和900℃下的变形激活能分别为209.25,196.01,194.01和130.40 kJ.mol-1;在750～850℃下的激活能接近于α-Ti的自扩散激活能(200 kJ.mol-1),表明在750～850℃的变形由α-Ti自扩散参与的动态再结晶控制;在900℃下激活能略低于β-Ti的自扩散激活能(160 kJ.mol-1),说明在900℃下的变形机制由β相的动态回复控制。综合考虑变形行为与组织细化因素,温度在750～850℃,变形速率在0.01～0.10 s-1范围为良性热加工区域。
In order to study the thermal deformation behavior of the Ti-6Al-7Nb alloy for surgical implant, the Gleeble 2000 thermal simulator was used to measure the strain rate of the Ti-6Al-7Nb alloy at 750-900 ℃ and the strain rate of 0.001-10.000 s-1 In the range of isothermal hot compression experiments carried out under argon protection, the use of metallographic and transmission electron microscopy to observe the thermal deformation of the organization; by calculating the deformation activation energy Ti-6Al-7Nb alloy deformation during hot compression process mechanism. The results show that the rheological stress shows the phenomenon of rheological softening after the work-hardening stage. At the low strain rate ε = 0.001 ~ 0.100 s-1, the softening of the material is mainly affected by the α-phase dynamic recrystallization. The higher strain rate ε = 1 ~ 10 s-1, the material basically did not recrystallize, the softening is due to the adiabatic effect of titanium alloy in the deformation process. Arrhenius equation was used to calculate the deformation activation energies of alloy at 750, 800, 850 and 900 ℃ respectively, 209.25, 196.01, 194.01 and 130.40 kJ · mol-1. The activation energy at 750-850 ℃ is close to that of α-Ti (200 kJ · mol-1), indicating that the deformation at 750 ~ 850 ℃ is controlled by the dynamic recrystallization of α-Ti self-diffusion. The activation energy at 900 ℃ is slightly lower than the self-diffusion activation energy of β-Ti .mol-1), indicating that the deformation mechanism at 900 ℃ is controlled by the dynamic response of β phase. Considering the deformation and microstructure refinement factors, the temperature ranged from 750 ℃ to 850 ℃, and the deformation rate ranged from 0.01 to 0.10 s-1.