研究了大变形量冷轧Ti-15-3合金的时效析出行为和时效过程中力学性能的变化.冷变形使Ti-15-3合金中形成部分纳米晶.冷变形合金在450～650℃时效时,从β相纳米晶区析出极为细小的针状α相,而从β相非纳米晶区析出的α相随着时效温度的升高由针状逐渐长大为条状,进而演变为凸透镜状.冷变形合金在450℃时效4 h后,硬度达到了峰值,HV为5328 MPa.450℃时效时在硬度峰值处同样达到了强度峰值,屈服强度和抗拉强度分别可高达1483和1562 MPa.时效温度升高,达到峰值硬度的时间缩短,硬度值大幅度下降.650℃时效后的强度和硬度均低于时效前,粗大的透镜状析出相、纳米晶的长大以及位错密度的急剧下降是650℃时效时硬化效果消失的主要原因.不同时效工艺下的强度和硬度的变化规律相似,性能的变化与时效过程中析出相的状态有关.
The precipitation behavior of α phase from β phase and the variation of mechanical properties during aging in the severely cold rolled alloy were studied. The results show that nanostructure is formed in some regions of the cold deformed alloy, α phases precipitating from β nanostructure region are thin-needle like during aging from 450 ℃ to 650 ℃ and those from β non-nanostructure region grow from the needle to the lath-shaped and finally become lenticular plate. After cold rolling and heat treatment at 450 ~C for 4 h, the hardness of the alloy reaches the peak value (5328 MPa). The yield strength and ultimate strength of the alloy aged at 450℃ for 4 h are 1483 and 1562 MPa, respectively. The aging time for peak value is shortened and the hardness decreases sharply with the increase of aging temperature. The strength and hardness of the alloy after aging at 650 ℃ is lower than that before aging. This is attributed to the coarse thin-plate precipitates, the growth of nanostructure crystals and the decrease of dislocation density in the alloy during aging at 650 ℃. The change tendency of the strength and the hardness of the alloy treated by different aging procedures are similar and they are related to the state of the precipitates formed during aging.
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