固溶-时效热处理工艺对近β钛合金显微组织演化与力学性能的影响

摘要

The microstructural evolution, mechanical properties and fracture mechanism of a Ti-5Al-5Mo-5V-3Cr-1Zr (Ti-55531) alloy after solution (760-820℃) plus aging (580-640℃) treatments were investigated. The results show that the volume fraction of the primaryα (αp) phase decreases with the increase of solution temperature, and the length of the secondaryα phase (αs) decreases while its width increases with the increase of aging temperature. Yield and tensile strengths decrease with the increase of solution temperature, while increase with the increase of aging temperature. A good balance of tensile strength and ductility of the alloy is obtained under solution of 800 ℃ for 2 h plus aging of 640℃ for 8 h, in which the tensile strength is 1434 MPa and the elongation is 7.7％. The coarseningαs phase makes crack propagation paths deflected and tortuous, which increases the crack propagation resistance and improves the ductility and fracture toughness.%研究钛合金Ti-5Al-5Mo-5V-3Cr-1Zr(Ti-55531)在不同固溶(760～820℃)与时效(580～640℃)热处理条件下的显微组织演化、力学性能及断裂机理.结果表明,初生 α 相(αp)的体积分数随固溶温度的升高而降低,而次生 α 相(αs)的长度随时效温度升高而降低,其宽度则随时效温度升高而增加.Ti-55531合金的屈服强度和抗拉强度随固溶温度升高而降低,但随时效温度的升高而增大.合金在800℃固溶2 h、640℃时效8 h的条件下获得的抗拉强度(1434 MPa)与韧性(伸长率7.7％)达到最优匹配.随时效温度和时间的增加,αs相发生粗化,使微观裂纹扩展路径变得曲折、崎岖,从而提高裂纹扩展阻力,最终提高合金的韧性与断裂韧性.