2A70耐热铝合金铸态组织分析及均匀化工艺研究

Microstructure of as-cast billet and homogenization treatment of 2A70 heat-resistance aluminum alloy

摘要:

本文采用光学显微镜(OM)、扫描电子显微镜(SEM)、差示扫描量热(DSC)及X射线衍射分析仪(XRD)，分析2A70耐热铝合金的铸造组织，研究其合理的均匀化热处理制度。同时，采用Thermo-Calc热力学计算软件，模拟Al-2.4Cu-1.5Mg-1.1Fe-1.1Ni合金的非平衡凝固路径，分析2A70合金在凝固过程中的析出相种类，并计算该合金低熔点共晶组织的转变温度，为研究2A70合金的铸态组织及均匀化工艺提供理论依据。结果表明：模拟计算所得2A70合金在凝固过程中主要析出α-Al、Al2CuMg、Al2Cu、Al9FeNi、Al7Cu4Ni及Al7Cu2Fe，与实验分析结果一致，且计算所得低熔点共晶组织转变温度可近似替代实验结果；该合金合理的均匀化热处理制度为490℃?2~16h 520℃?2h，在高温长时均匀化过程中非平衡共晶组织得到较彻底的回溶，Al9FeNi、Al7Cu4Ni及Al7Cu2Fe难溶相未发生明显变化。

Abstract:

The microstructure of casting billet and the homogenization treatment were investigated by optical microscopy (OM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and X-ray diffraction analysis (XRD) respectively. Meanwhile, using the Thermo-Calc software, the solidification path for the Al-2.4Cu-1.5 Mg-1.1Fe-1.1Ni alloy was calculated. On this basis, the phases precipitated during solidification were analyzed and the transition temperature of the non-equilibrium eutectic phases was also calculated, which provided a theoretical basis for the research on microstructure and homogenization process. According to the calculated results, the α-Al、Al2CuMg、Al2Cu、Al9FeNi、Al7Cu4Ni and Al7Cu2Fe phases are exist in the 2A70 alloy, which in accordance with the experimental findings. In addition, the transition temperature for the non-equilibrium eutectic phases can be approximate substituted by the computed data. The reasonable homogenization treatment process for the investigated alloy is 490℃?2~16h 520℃?2h. During the high-temperature and long-time homogenization process, the non-equilibrium eutectic phases are dissolved completely and the Al9FeNi、Al7Cu4Ni and Al7Cu2Fe changes a little.