【摘要】 通过显微组织观察和拉伸试验研究添加0.02%Sn(质量分数)对Al-4Cu合金在573 K高温热暴露过程(100 h)中θ′向θ相转变机制和高温强度的影响。研究结果表明，Sn微合金化能完全改变Al-4Cu合金在持久热暴露过程中θ′相向θ相的相转变机制。在未添加Sn的Al-4Cu合金中，棒状θ相在粗化后的盘状θ′相的表面形核和生长。然而，当添加少量Sn后，θ相首先在β-Sn颗粒上异质形核，然后形成粗大的针状相。由于Sn微合金化能提高Al-4Cu合金中θ′相的数密度并降低其尺寸，因此，Al-4Cu合金在T5状态下的室温和573 K高温下的屈服强度得到显著提高。然而，Sn微合金化能同时促进持久热暴露过程中θ′相向θ相的转变，导致Al-4Cu合金在热暴露后的高温(573 K)强度显著降低。更多还原

【Abstract】 The effects of 0.02 wt.% Sn addition to Al-4Cu alloy on the phase transformation mechanism from θ′ to θ phase during a long-time heat exposure at 573 K for 100 h and on high temperature strength were studied through microstructure observation and tensile test. It is found that Sn micro-alloying in Al-4Cu alloy completely changes the mechanism of θ′ → θ phase transformation during the long-time heat exposure. In the alloy without Sn addition, rod-like θ phase nucleates and grows on the surface of coarsened disc-like θ’ phase. However, with Sn-micro-alloying, θ phase firstly heterogeneously nucleates on β-Sn particles, and then grows into much coarser needle-like phase. Trace addition of Sn significantly increases the yield strength of T5-samples at both room temperature and 573 K, because addition of Sn increases the number density of θ′ particles and reduces its size. But, after the long-time heat exposure, the high temperature(573 K) strength of Al-4Cu alloy is severely degraded because Sn accelerates the phase transformation from θ′ to θ phase.更多还原