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In this paper, the effect of Y content on hot tearing properties of cast Al-Cu-Mg alloy was studied. The effect and mechanism of Y on hot tearing of cast Al-4.4Cu-1.5Mg-0.15Zr alloy were studied by analyzing the microstructure evolution, phase structure, solidification process and hot tearing sensitivity coefficient of the alloy with different Y additions, and determined the appropriate amount of Y element. The results showed that Y improves hot tearing resistance of Al-4.4Cu-1.5Mg-0.15Zr alloy by refining microstructure and reducing the solidification temperature range. The suitable amount of Y is 0.15 wt%. At this time, a certain amount of Al 6 Cu 6 Y low melting point phase is formed in the alloy, and the grain structure is the smallest, which significantly improves the hot tearing resistance of Al-4.4Cu-1.5Mg-0.15Zr alloy. The microstructure coarsening and hot tearing tendency increase with increasing Y content. The experimental results are basically consistent with the hot tearing sensitivity predicted by the Clyne-Davies model.

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The hot deformation behavior and processing maps of the casting NiTi alloy were studied at the deformation temperature of 650–1050 °C and the strain rate of 5 × 10−3–1 s−1 by Gleeble-3800 thermal simulating tester. The variation of the strain rate sensitivity exponent m and the activation energy Q under different deformation conditions (T = 650–1050 °C, ε˙ = 0.005–1 s−1) were obtained. The formability of the NiTi alloy was the best from 800 °C to 950 °C. The constitutive equation of the casting NiTi alloy was constructed by the Arrhenius model. The processing map of the casting NiTi alloy was plotted according to the dynamic material model (DMM) based on the Prasad instability criterion. The optimal processing areas were at 800–950 °C and 0.005–0.05 s−1. The microstructure of the casting NiTi alloy was analyzed by TEM, SEM and EBSD. The softening mechanisms of the casting NiTi alloy were mainly dynamic recrystallization of the Ti2Ni phase and the nucleation and growth of fine martensite.

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