时效温度对Ti1023和Ti5553合金a相析出行为与力学性能的影响规律

The effect of microstructure and mechanical properties in Ti1023 and Ti5553 alloys during different aging temperature

摘要:

本文研究了Ti1023和Ti5553钛合金经过固溶与低温时效处理(ST-SQA)获得的微观组织和析出硬化行为。采用扫描电镜和透射电镜观察了不同温度时效处理后α相的析出形貌以及分布特点，统计了时效析出次生α相的析出密度和宽度随时效温度的变化情况，并测试了合金的维氏硬度。结果表明： Ti1023合金时效处理时次生α的析出温度低于Ti 5553合金。Ti1023合金在300℃时效时α相已经析出，400℃时α相析出密度到达峰值；Ti5553合金在450-500℃时效α相开始析出，在550℃时效α相的析出密度达到峰值。Ti1023合金硬度随着时效温度的增加先升后降，400℃时效硬度最高；在相同的时效温度范围，Ti5553合金硬度变化出现双峰规律，硬度峰值分别对应于350℃和550℃时效温度。两种合金的硬度变化规律源于合金时效中第二相的析出行为：时效温度低于400℃，Ti1023合金的硬度取决于α相和?相，而Ti5553合金的硬度取决于?相；温度高于400℃，两种合金的硬度主要取决于次生α相的数量与尺寸。

Abstract:

The microstructures and precipitation hardening of Ti1023 and Ti5553 alloys in the same solution treatment and step-quench aging treatment (ST-SQA) have been studied. The morphology of α phase about precipitation and distribution in different aging treatment were observed carefully by using SEM and TEM, and the variation of density and width of secondary α phase were analyzed. The hardness of these two alloys was measured. The result shows that: Ti1023 alloy is more likely to precipitate α phase than Ti5553 alloy due to low stability of ? phase. Ti1023 alloy precipitates α phase at 300℃ aging and get the maximum density of precipitation at 400℃,while Ti5553 alloy precipitates α phase at 450℃, and get the maximum density of precipitation at 550℃. As for Ti1023 alloy, the peak of hardness is obtained at 400℃ aging, while as for Ti5553 alloy, double peaks of hardness are shown at 350℃ and 550℃ aging, respectively. The variation of hardness was caused by the precipitation of secondary phase in ? phase for different aging temperatures. When aging temperature is below 400℃, the hardness of Ti1023 alloy depends on both α phase and ω phase, and the hardness of Ti15553 alloy depends on only ω phase. As aging temperature is over 400℃, the hardness of both Ti1023 and Ti5553 alloys depend on the density of precipitation and the size of α phase.