时效工艺对Ti75合金显微组织及力学性能的影响

Influence of Aging Treatment on Microstructure and Mechanical Properties of Ti75 Alloy

为了模拟Ti75合金焊接接头热影响区的组织,对其进行了β相区淬火处理。淬火后的Ti75合金为片层组织,采用不同工艺对其进行时效处理,研究了时效温度、时效时间对片层组织Ti75合金显微组织和力学性能的影响。结果表明:β相区淬火后Ti75合金的屈服强度、抗拉强度随时效温度升高而降低,冲击韧性随时效温度升高先降低后升高。时效温度较低时,马氏体α′相分解为稳定的α相和β相,以弥散强化作用为主;随着时效温度的升高以及时效时间的延长,片层组织发生合并长大现象,达到一定程度时,软化作用占据主要地位。断口分析表明,淬火态断口呈现准解理平面特征,随着时效过程中软化作用的增强,解理平面上出现浅韧窝,塑性增加。

In order to simulate the microstructure of heat affected zone of Ti75 alloy welded joint,quenching treatment in β phase temperature zone was carried out on Ti75 alloy.Then different aging treatments were carried out on the quenched Ti75 alloy which has a lamellar structure.The effects of aging temperature and aging time on the microstructure and mechanical properties of the lamellar Ti75 alloy were studied.The results show that the yield strength and tensile strength of Ti75 alloy decrease with the increase of aging temperature,and the impact toughness decreases first and then increases with the increase of aging temperature.At lower aging temperature,martensite α′ phases are broken down into dispersive stable α and β phases,which result in dispersion strengthening.With the increase of aging temperature and aging time,the lamellar α phases coalesce and grow up.When it reaches a certain degree,the softening effect takes the dominant position.The results of fracture analysis show that the quenched fracture surface presents the quasi cleavage plane feature.With the increase of softening effect during aging,shallow dimples appear on the cleavage plane and the plasticity increases.