等径弯曲通道变形制备超细晶铜的热稳定性

室温下采用等径弯曲通道变形(Equal Channel Angular Pressing,ECAP)C方式进行了纯铜(99.95%)12道次挤压变形。通过等温和等时退火,研究ECAP变形后铜的退火行为,并研究了等径弯曲通道变形和退火后纯铜的显微硬度和显微结构变化。分析了ECAP应变量、退火时间和退火温度对超细晶铜的再结晶行为、抗软化性能的影响。结果表明:ECAP变形后的超细晶铜在退火过程中,表现出不连续再结晶现象;ECAP降低了铜的热稳定性,变形道次越高再结晶温度越低。退火后稳态晶粒尺寸随变形道次的增加而细化,硬度值随变形道次的增加而增大,回归分析表明,晶粒尺寸与硬度之间的关系符合Hall-Petch公式。

Thermal stability of ultra-fine grained copper processed by equal channel angular pressing

Annealing behavior of pure copper(99.95%) after equal channel angular pressing(ECAP) was investigated by isothermal annealing and isochronal annealing.The copper were deformed at room temperature by ECAP up to 12 passes via rout C and its microstructure and microhardness evolution after deformation and annealing were studied.The effect of ECAP strain,annealing time and annealing temperature on evolution of microstructure and hardness of the ultra-fine grained(UFG)copper was analyzed.The results show that the microstructure of the ECAP processed copper exhibits discontinuous recrystallization during subsequent annealing.The study reveals a very low thermal stability of the ECAP processed pure copper.The temperature for discontinuous recrystallization of ECAP deformed samples is found to substantially decrease with increasing number of passes.The microhardness of the deformed copper is improved with increasing number of ECAP passes owing to the decreasing of the steady-state grain size after annealing.Regression analysis shows that the relationship between grain size and hardness is in agreement with Hall-Petch expression.