渗碳工艺下纯Ti板显微组织及晶粒长大动力学

Analysis on Microstructure and Dynamics of Grain Growth of Titanium Sheet under Carbonization Technique

研究不同渗碳工艺对纯Ti板微观组织和表面强化的影响,分析了晶粒长大阶段动力学特征。根据不同热处理温度(600、700、800℃)及时间(3、6、9h)下光学显微组织的转变规律,纯Ti板渗层硬度随渗碳温度升高和保温时间延长的变化趋势,确定500℃+1h真空预处理和700℃+6h渗碳处理为较佳渗碳工艺。分析了长大阶段晶粒平均尺寸变化,计算不同温度下晶界迁移速度,确定长大动力学时间指数和晶粒长大激活能分别为0.5、72.02kJ·mol-1,表明晶粒长大阶段激活能主要由空位激活能和晶界扩散激活能共同作用引起。

The influence of different carbonization techniques on microstructure and surface strengthen of titanium sheet and the kinetics analyses of grain growth were investigated in this paper. According to the transition structures, observed under optical microscope, obtained by different heat-treatment temperatures （600 ℃, 700 ℃, 800℃） and holding times （3 h, 6 h, 9 h）, and the transformed trend of carbonization hardness with the increase of temperature and time, the optimal carbonization technique was confirmed, that was vacuum pretreatment （holding 1 h at 500 ℃ in 10^-3 Torr） and then carbonization （holding 6 h at 700 ℃ ）. The variety of average grain sizes at the growth stage was analyzed. The migration velocities of grain boundary in different temperatures were calculated, and the time exponent of grain growth kinetics and active energy were confirmed to be 0.5, 72.02 kJ · mol^-1, respectively. The phenomena indicate that active energy at the growth stage was controlled by the combination effect of vacancy activation energy and grain boundary diffusion activation energy.