The research of casting properties especially the fluidity and hot tearing susceptibility is crucial for cast aluminum alloys. The fluidity and hot tearing susceptibility of two aluminum alloys were studied by three different methods (steel mold cast, thermal analysis and thermodynamic calculation), and the results were discussed in detail. The flow length and hot tearing susceptibility (HTS) of AlSi3.5Mg0.5Cu0.4 and A356 alloys were compared by using the spiral mold and constrained-rod cast mold, respectively. The solidification range (ΔT_S) and dendrite coherency point (T_DCP) were measured by cooling curve thermal analysis to explain the difference in fluidity of the two alloys, which reveals that the alloy with a smaller ΔT_S and a lower T_DCP will show a better fluidity. The thermal analysis results show that the alloys with a shorter “hot tearing sensitive range” can obtain lower hot tearing susceptibility. A hot tearing mechanism of the two aluminum alloys was proposed, that is, the hot tear initiates at the end of solidification and propagates along the liquid film. The thermodynamic calculation with Thermo-Calc software was proved to be an accurate and simple method to compare and analyze the fluidity and hot tearing susceptibility of aluminum alloys.

研究铸造性能，特别是流动性和热裂敏感性对铸造铝合金至关重要。通过三种不同的方法（钢模铸造、热分析和热力学计算）研究了两种铝合金的流动性和热裂敏感性，并对结果进行了详细讨论。分别使用螺旋模具和约束棒铸造模具比较了AlSi3.5Mg0.5Cu0.4和A356合金的流动长度和热裂敏感性(HTS)。通过冷却曲线热分析测量凝固范围（Δ T _S）和枝晶相干点（T _DCP）来解释两种合金流动性的差异，表明具有较小Δ T _S的合金T _DCP越低，流动性越好。热分析结果表明，具有较短“热裂敏感范围”的合金可以获得较低的热裂敏感性。提出了两种铝合金的热撕裂机理，即热撕裂在凝固结束时开始并沿液膜传播。Thermo-Calc 软件的热力学计算被证明是一种准确、简单的方法来比较和分析铝合金的流动性和热裂敏感性。