退火温度对铪棒组织与性能的影响

Effects of Annealing Temperature on Microstructure and Properties of Hafnium Bars

采用热轧加冷旋锻的方式将∅60 mm铪棒坯加工至∅13.3 mm,然后分别在440、600、740、900、1040℃下保温1 h进行真空退火处理,对比研究了不同退火温度下铪棒的显微组织、室温及高温拉伸性能、高温拉伸断口形貌。结果表明,随着退火温度的升高,晶粒逐渐长大,但孪晶组织并不会随着退火温度升高而完全消失,相反,在高温退火时铪棒组织中容易形成退火孪晶;铪棒的抗拉强度、屈服强度随着退火温度的升高逐渐降低,抗拉强度的降速出现了先慢后快的现象,屈服强度反之。440、600、740℃高温拉伸断口形貌为多韧窝态的韧性断裂,韧窝大小、密度略有不同,而900、1040℃退火后,断口形貌存在解理台阶并有河流状花纹,为脆性断裂。

The ∅60 mm hafnium billet was processed to∅13.3 mm by hot rolling and cold rotary forging,and then vacuum annealing was carried out at 440,600,740,900 and 1040℃for 1 h respectively.The microstructure,room temperature and high temperature tensile properties,high temperature tensile fracture morphology of the hafnium bars under different annealing temperatures were studied comparatively.It is shown that with the increase of annealing temperature,the grain gradually grows,but the twin structure does not completely disappear with the increase of annealing temperature,in contrast,annealed twins are easily developed in the hafnium bar at high temperature;the tensile strength and yield strength of the hafnium bar gradually decrease with the increase of the annealing temperature,with a slow and then fast decline of the tensile strength while the yield strength is otherwise.The tensile fracture morphologies at 440,600 and 740℃present ductile fracture feature with many dimples,whose fracture size and density are slightly different.However,after annealing at 900℃and 1040℃,the fracture morphologies appear as cleavage steps and river-like pattern,which are brittle fractures.