淬火无析出区对Al-Zn-Mg-Cu合金断裂行为的影响

Effect of precipitate free zone quench-induced on fracture behavior of Al-Zn-Mg-Cu alloys

根据超高强铝合金淬火、时效组织透射电镜观察结果,以及合金断裂行为与断口形貌分析,提出了一种Al-Zn-Mg-Cu合金产生延性断裂的物理模型。对平衡相、基体沉淀相、无析出微区的断裂行为进行了分析。研究结果表明,在晶内同步变形条件下,平衡相粒子最先断裂;晶内沉淀区内裂纹的形成与扩展早于无析出区,沉淀区内初始孔洞扩展与聚合,导致沉淀区断裂,这是合金断裂的主要原因;无析出区最后断裂。引起淬火敏感性的平衡相粒子,不是造成合金断裂的直接原因,粒子周围的无析出微区起到了限制裂纹扩展和协调变形的作用,是合金形成延性拉伸断口的原因。

An intercrystalline ductile fracture physical model of ultra-high-strength Al-Zn-Mg-Cu alloy was given and the stage fracture behaviors of equilibrium phase, matrix precipitation and microzone of precipitate free zone （PFZ） were analyzed by TEM observation of the quenched and aged microstructures, the fracture behavior and morphology of Al-Zn-Mg-Cu alloy. The results show that under the synchro deformation circumstances, the equilibrium phase particles are fractured firstly, the formation and extension of fracture in intercrystalline precipitate zone are earlier than those in PFZ; the matrix precipitation is fractured due to the coaction between the primary cavities produced by equilibrium phase particles in precipitation zone and the secondary cavities produced by precipitation, this is the major fracture reason of the alloy; the precipitate free zone is fractured lastly. The equilibrium phase particles that induce the sensitivity of the quenching are not the direct reason that causes the alloy fracture; the microzone of PFZ around particles limits crack extension and coordinates deformation, this causes the formation of the ductile tension fracture.