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在备有拉伸装置的扫描电镜下,观察了 Al—2.56 Li—1.29Cu 合金拉伸变形及断裂过程。观察结果表明,在固溶淬火及190℃时效状态下,主要析出相为δ’相。随着时效时间的延长,拉伸断口逐渐由韧窝穿晶型向沿晶突脊型及沿晶韧窝型过渡。在固溶状态下,当拉伸应力超过届服强度以后,出现平直滑移带及交叉滑移带;拉伸裂纹在晶内滑移带及晶界处萌生,并主要沿滑移带扩展。欠时效状态下,δ’相的析出量增多,使共面滑移加剧,交叉滑移带难于形成;裂纹除沿晶界扩展外,也有少部分沿滑移带扩展。在达到峰时效以后,交叉滑移带消失;裂纹在三角晶界处萌生并沿晶界扩展。
The tensile deformation and fracture process of Al-2.56 Li-1.29Cu alloy were observed under a scanning electron microscope equipped with a tension device. The results show that in the solution quenching and 190 ℃ aging state, the main precipitation phase δ ’phase. With the extension of aging time, the tensile fracture gradually transforms from dimpled ridge to intergranular ridge and intergranular dimples. In the solution state, when the tensile stress exceeds the service strength, the flat slip band and the cross slip band appear. The tensile cracks initiate in the slip band and the grain boundary, and mainly extend along the slip band . Under the undeveloped state, the amount of δ ’phase precipitates increases, which aggravates the coplanar slip and crossover slip band is difficult to form. In addition to the grain boundary extension, there are also a few cracks extending along the slip band. After reaching peak aging, the cross-slip band disappears; the crack begins to sprout at the triangular grain boundaries and grows along the grain boundaries.