摘要:
Al-Cu-Ge合金是典型的三元共晶体系,在工业上有重要的应用价值,对其进行研究有助于了解该合金的热物理性质和提高该合金的结构性能.本文选择了Al55Cu10Ge35, Al70Cu10Ge20和Al80Cu10Ge10三种成分合金作为研究对象,对合金的固态比热和热膨胀系数进行了测量,并对比分析了合金在近平衡凝固和落管快速凝固条件下的组织特征和凝固路径.研究发现,合金比热随Al含量的增大和Ge含量的减少而增大.这三种成分合金的软化温度均为666 K,物理热膨胀系数α在370-650 K温度范围内基本一致,约为1.5×10-5 K-1.近平衡凝固条件下合金凝固过程中最后一步反应生成的均为(Al)+(Ge)二相共晶而不是三元共晶,这表明(Al)、(Ge)和CuAl2相在这三种成分的Al-Cu-Ge合金中难以同时形核并协同生长.然而,在快速凝固条件下,初生相的形核和生成受到抑制,合金中更易于形成二相共晶和三元共晶组织.
Abstract:
Al-Cu-Ge alloy system, a typical ternary eutectic alloy system, has been used widely in the industries. Our research is helpful for better understanding its thermophysical properties and improving its structural performance. In this paper, the specific heat values and thermal expansion coefficients of Al55Cu10Ge35, Al70Cu10Ge20 and Al80Cu10Ge10 alloys are investigated. The microstructural characteristics and the solidification paths of these alloys under near-equilibrium solidification and rapid solidification conditions are studied comparatively. Their specific heat values increase as Al content increases and Ge content decreases. The softening temperature is 666 K, and the thermal expansion coefficient fluctuates around 1.5 × 10-5 K-1 in the temperature range of 370-650 K. Under a near-equilibrium solidification condition, the last formation microstructure is (Al)+(Ge) pseudobinary eutectic instead of ternary eutectic. This means that (Al), (Ge), and CuAl2 phases are difficult to nucleate simultaneously or grow cooperatively. In comparison, during rapid solidification, the nucleation of primary phase is depressed, pseudobinary eutectic and ternary eutectic are much easier to form in these alloys.
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