Analysis of β´(Cu4Ti) Precipitation During Isothermal Aging of a Cu-4wt.%Ti Alloy

This work analyzed experimental and numerically the growth kinetics of β´precipitation of a Cu-4wt.%Ti alloy after aging at 400, 500 and 600 ºC for times from 0.0166 h to 200 h. Results indicated that the precipitation process is almost controlled by nucleation and growth during aging at 400 ºC, originating a slow growth kinetics of precipitation. In contrast, the coarsening of precipitates dominates the precipitation process during aging at 500 and 600 ºC. The interfacial energy of interface between the a matrix phase and β´ precipitates was determined to be about 0.1135, 0.0980 and 0.0725 Jm-2 for aging at 400, 500 and 600 ºC, respectively. These values suggest a coherent interface which is in agreement with the flat faces of β´ cuboid precipitates. Calculated Time-Temperature-Precipitation diagram for the β´ precipitation indicated good agreement with experimental results. Precipitation hardening was higher for the slower growth kinetics of precipitation.

本研究通过实验与数值模拟手段，分析了Cu-4wt.%Ti合金在400、500及600℃下时效0.0166 h至200 h过程中β´析出相（β´ precipitate）的生长动力学。结果表明，在400℃时效时，析出过程几乎由形核与生长主导，析出生长动力学较为缓慢。与之相反，在500℃与600℃时效时，析出相的粗化过程主导了整个析出进程。测得α基体相与β´析出相之间的界面能在400、500、600℃时效时分别约为0.1135、0.0980及0.0725 J·m⁻²，该数值表明界面为共格界面，与β´立方形析出相的平整晶面形貌相符。针对β´析出相计算得到的时间-温度-析出图（Time-Temperature-Precipitation diagram，TTP）与实验结果吻合良好。析出强化效果随析出生长动力学减慢而增强。