摘要
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。
Isothermal hot compression tests were carried out in argon atmosphere in the strain rate range of 0.001~10.000 s-1 and the temperatures range of 750~900 ℃ by using Gleeble 2000 simulator for implant biomedical Ti-6Al-7Nb alloy to obtain the hot deformation behaviors.Deformed microstructures were observed by optical and electron transmission microscope.By calculation of deformation activation energy,the deformation mechanisms in hot compression process were analyzed.The results showed that the true stress-true strain curves became flow softening after undergoing primary work-hardening stage.Softening mechanism was attributed to the dynamic recrystallization of α phase at low strain rate of 0.001~0.100 s-1 and adiabatical effect at high strain rate of 1~10 s-1.According to Arrhenius equation,the activation energies at 750,800,850 and 900 ℃ were calculated to be 209.25,196.01,194.01 and 130.40 kJ · mol-1,respectively.The calculated activation energy at 750~850 ℃ was about 200 kJ · mol-1 which was close to self diffusion activation energy of β-Ti and suggested that the dynamic recrystallization of α phase by Ti self diffusion was the rate-controlling step.The activation energy at 900 ℃ was 130 kJ · mol-1,less than self diffusion activation energy in β-Ti.This indicated that the deformation was controlled by dynamic recovery in β-phase.Considering workability and microstructural control,the optimum hot deformation conditions were determined in the temperature range of 750~850 ℃ and strain rate range of 0.01~0.100 s-1.
出处
《稀有金属》
EI
CAS
CSCD
北大核心
2012年第2期218-223,共6页
Chinese Journal of Rare Metals
基金
国家自然科学基金资助项目(30470486)
关键词
生物钛合金
热压缩
真应力-真应变曲线
显微组织
激活能
变形机制
biomedical titanium alloy
hot compression
true stress-strain curves
microstructure
activation energy
deformation mechanism
