热处理工艺对Ti-48Al-2Cr-2Nb合金变形不均匀行为的影响

Effect of Heat Treatment Process on Uneven Behavior of Ti-48Al-2Cr-2Nb Alloy

利用循环热处理工艺,在α+γ相区(1240℃,1 h)对合金进行四次循环处理,然后在α单相区进行固溶(1320℃,5 min)处理,以获得小片层组织Ti-48Al-2Cr-2Nb合金,并对不同热处理工艺下合金的变形不均匀行为及损伤分布进行研究。结果表明:上述热处理工艺将晶粒尺寸由1260μm细化至250μm左右,成功得到小片层组织,硬度从HV0.5250提高至HV0.5280以上。不同热处理工艺下的合金在变形过程中均存在不同程度的变形不均匀现象,且损伤集中在自由变形区。热处理获得的混合组织和小片层组织材料各变形区再结晶程度更充分,变形均匀性明显优于铸态组织材料。铸态组织材料自由变形区的损伤值达到0.35以上;混合组织材料为0.27~0.30;小片层组织材料损伤值最小为0.25左右。循环热处理最终获得的小片层组织变形最均匀,变形后的组织中没有出现明显的微观缺陷。

The Ti-48 Al-2 Cr-2 Nb alloy with small lamellar structure was obtained by four cycles in theα+γphase region(1240℃,1 h)and solid solution treatment(1320℃,5 min)in the a single phase region.The unevenness deformation and damage distribution were studied at different heat treatment processes.The results showed that the grain size was refined from 1260 to 250μm by the above heat treatment processes.So small lamellar organizations were obtained successfully and the hardness value was increased from HV0.5250 to HV0.5280.During the deformation process,the alloys,under different heat treatment processes,had different degrees of the unevenness deformation,and the damage was concentrated in the free deformation zone.The deformation zone of the mixed structure and the small lamellar tissue material obtained by the heat treatment was more fully reciystallizing,thus the deformation uniformity was significantly better than the as-cast inicrostructure.The damage value of the as-cast microstructure material was above 0.35 in the free deformation zone and was between 0.27 and 0.30 in the mixed tissue material.The smallest damage value was about 0.25 in the small lamellar tissue material.Among them,the microstructure of the small lamellar obtained by the cyclic heat treatment was the most uniform,because the microdefect was not obviously observed in the inicrostructure after deformation.