2099铝锂合金微观组织及性能的演变

Evolution of microstructures and properties of 2099 Al-Li alloy

对2099铝锂合金微观组织及性能在热机加工过程中的演变进行研究。研究结果表明:枝晶粗大,晶界偏析严重的铸态合金经双级均匀化(510℃/12 h+530℃/36 h)处理后,树枝晶消失,晶界偏析基本消除,晶界上残余有少量的Al Cu Fe Mn/Al Cu Mn颗粒。均匀化后的铸锭在450℃进行热挤压,获得直径为16 mm的合金棒。合金经固溶处理后,平行于挤压方向上,中心区域形成强的{111}?112?织构和次强的{111}?110?织构,表层区域形成{112}?110?织构。中心区域的织构强度较表层的强。合金心部和表层硬度(HV)分别为95和120。在峰时效条件下,大量的T1和δ′相以及少量的θ′相在基体中析出。合金相应的抗拉强度,屈服强度和伸长率分别为613 MPa,597 MPa和7.9%。随着时效时间的延长,合金应力腐蚀敏感性降低。在过时效条件下,合金获得理想的抗应力腐蚀性能,强度损失率为5.5%。

The evolution of microstructure and properties of 2099 A1-Li alloy during thermal mechanical process were investigated. The results show that coarsen dendrites and severe grain boundaries segregation of as-cast alloy are eliminated by two-step homogenization （510 ℃/12 h＋530 0C/36 h）, and a few of small A1CuFeMn/A1CuMn particles remain around the grain boundaries. The homogenization alloy is extruded to rod with 16 mm diameter at 450 ℃. Along the extrusion direction, central zone of solution heat treated alloy formed major intense { 111 } （112） texture and secondary intense { 111 } （110） texture, surface zone formed { 112} （110） texture, and the intension of texture of central zone is higher than that of surface zone. The hardness of central zone and surface zone is 95 and 120, respectively. In the peak-aged condition, a great number of T1 and 5＇ phases as well as a few 0＇ phases precipitated in the matrix, the corresponding tensile strength, yield strength and elongation of alloy are 613 MPa, 597 MPa and 7.9%, respectively. The stress corrosion cracking （SCC） susceptibility of alloy decrease with aging time, and the strength loss rate of over-aged alloy is 5.5%.