预退火对纯钽再结晶行为的影响

The effect of pre-annealing on recrystallization behavior of purity tantalum

将87%单向轧制钽板分别在800℃预退火0 min、5 min、15 min和30 min,然后把所有样品在1 200℃退火30 min使其发生完全再结晶。采用电子背散射衍射(EBSD)、金相显微和显微硬度等技术表征了不同预退火时间后的微观组织及后续高温退火再结晶微观组织,结果表明,预退火30 min后再经后续高温退火的样品,其表面和中心的再结晶晶粒尺寸最为均匀细小,这主要是由于随着预退火时间的增加,形变晶粒内部的储存能不断的释放,这在一定程度上降低了后续高温退火过程中晶粒的长大速率。同时,低温退火时亚晶形核是主要的再结晶机制,预退火时间到30 min时,{100}形变基体内部出现较多的{100}取向再结晶晶粒,这有效弱化了后续高温退火{111}再结晶织构的强度,从而有利于随机织构的生成。

A purity tantalum was unidirectional rolled to 87%reduction at room temperature.Afterward,four samples cut from the rolled plate were pre-annealed at 800℃for 0 min,5 min,15 min and 30 min,respectively,followed by a heating at 1 200℃for 30 min so that they were fully recrystallized.Then their microstructures were characterized by electron backscatter diffraction(EBSD),metallographic microscopy and microhardness techniques,respectively.Grains with small size and equiaxed shape appeared at the surface and center area of the sample which was pre-annealed for 30 min,and this mainly results from the gradual release of stored energy and the greatly reduced growth rate of grains with the increase of pre-annealing time.Meanwhile,subgrain nucleation mechanism plays an important role at the low-temperature annealing.Some{100}nuclei developed at{100}matrix weaken the{111}recrystallized texture,and thus lead to the development of microstructure in which the texture is weakened remarkably.