Analysis of the Fluidity and Hot Tearing Susceptibility of AlSi3.5Mg0.5Cu0.4 and A356 Aluminum Alloys

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 (Δ T 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 Δ T 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.