热加工对TiB增强钛基复合材料显微组织和力学性能的影响

Microstructure and Mechanical Properties of TiB Reinforced Titanium Matrix Composites with Heat Treatment

用原位自生技术制备了TiB增强的近α相钛基复合材料,利用光学显微镜（OM）、高温材料试验机和透射电镜（TEM）研究了热加工过程中此复合材料的魏氏组织演变和TiB晶须的取向变化,并测定了该复合材料的力学性能。研究结果表明：该复合材料的β晶粒尺寸和α片层的厚度随着压下率的增加而减小,这种变化使复合材料的显微组织得到了显著细化;随着压下率的增加,延伸方向上TiB晶须取向角的小角度概率密度值急剧增加,而大角度概率密度值急剧减小,加工方向上TiB晶须的概率密度值变为原来的6倍左右;热机械加工后该复合材料较之原来的铸态材料状态,屈服强度增加了25%左右,抗拉强度增加了30%左右,时效后屈服强度和抗拉强度都提高44%左右;若没有硅化物的析出,片层状α相的厚度值b对强度的影响较小,时效后硅化物沉淀析出使厚度值b成为重要的强化因素。

TiB reinforced titanium matrix with a near-α phase Ti-based composites were prepared by in-situ technologies.The evolution of the Wittgenstein microstructure,the orientation of the TiB whiskers and themechanical property during the hot working were investigated by means of optical microscope（OM）,high temperature material testing machine and transmission electron microscope（TEM）.The results showed that the β grain size and α thickness decreased with the increase of the reduction ratio.The microstructures of the TiB whiskers were significantly refined.With the increase in deformation amplitude,the value of probability density of small orientation angles of TiB whiskers along extension direction increased sharply,while the large angle probability density values decreased sharply,the probability of whiskers in the machining direction became six times that before.After hot working,the yield strength and the tensile strength increased by about 25% and 30%,and after aging,they both increased by about 44%.If there was no precipitation of silicide,the thickness of α-phase had little effect,the precipitation of silicide made the thickness become an important factor in strengthening after aging.