通过末端淬火、差示扫描量热仪(DSC)、扫描电镜(SEM)、透射电镜(TEM)、X线衍射仪(XRD)、光学显微镜(OM)和硬度等分析测试方法研究Al-8.0Zn-2.0Mg-1.6Cu铝合金的淬透性及淬火冷却过程中的微观组织演变。研究结果表明:随着冷却速度的降低,试样的硬度显著下降,其淬透深度约为40 mm,临界冷却速度约为3.8℃/s;淬火冷却过程中平衡态MgZn2(η)相析出是影响该合金淬透性的主要因素,其析出温度区间为438~215℃;平衡态MgZn2相在淬火冷却时先后经历晶界与晶粒内部2个过程的析出,析出峰值温度分别为387℃和342℃。
The hardenability and structures on Al-8.0Zn-2.0Mg-1.6Cu aluminum alloy were determined by end-quench test,differential scanning calorimetry(DSC),scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD),optical microscopy(OM) and hardness.The result shows that with the decrease of cooling rate the hardness decreases significantly,and the quenched depth is about 40 mm with critical cooling velocity 3.8 ℃/s.The precipitation of MgZn2(η) phases precipitating in 438-215 ℃ interval is the primary factor that affects the hardenability of this alloy during the quenching.The equilibrium state MgZn2 phases precipitate as two paths successively during the quenching: grain boundaries and inside the grains,with the peak temperature 387 ℃ and 342 ℃ respectively.