Al-1.98Li-1.78Cu-1.30Mg-0.10Zr合金微观组织、拉伸性能和断裂行为的研究

A STUDY ON THE MICROSTRUCTURE, MECHANICAL PROPERTIES AND FRACTOGRAPHY OF Al--1.98Li--1. 78Cu_- 1.30Mg_- 0.10Zr ALLOY

文中报道了对Al-1.98Li-1.78Cu-1.30Mg-0.10Zr合金组织、机械性能和断裂行为进行的研究。结果表明,合金在170℃/2h+190℃时效时有硬度双峰,屈服强度和抗拉强度也有类似的双峰,这主要是由δ′(Al_3Li)和S′(Al_2CrMg)的析出引起的。合金的强化相为δ′,S′和T_1(Al_2CuLi)。在欠时效阶段,析出的主要是δ′和少量沿位错析出的S′。在峰时效阶段,除析出δ′外,还有S′和T_1在基体中均匀析出,并且有晶间PFZ存在。拉伸试样的断裂以沿晶为主,但有少量由粗大第二相粒子诱发的韧窝存在于断裂表面上。

The microstructure, mechanical properties and fractography of Al-1.98Li-1.78Cu-1.30Mg-0.10Zr alloy has been studied. It has been found that a two-step aging of the alloy at 170℃ and at 190℃ caused a twostep mode of hardening. Changes in yield and tensile strength of the two-step aging at 170℃ and at 190℃ took a similar two-step mode. The two-step mode was caused by δ′(Al_3Li) and S′(Al_2CuMg) precipitates. The alloy was strengthened by a combination of δ′, S′and T_1 (Al_2CuLi). In underaged samples, the precipitates were mainly δ′, and a few S′precipitated at disloca- tions. In peakaged samples, besides δ′ precipitation, S′and T_1 precipitated homogeneously, and the pre- cipitate free zone was observed. The fracture mode of tensile samples were mainly intergranular, but a few dimples associated with the large second phase particles were distributed over fracture surface.