半凝固状態のアルミニウム合金の最大引張応力および伸び値の支配因子

To predict hot tearing of direct chill casting ingot, both the tensile constitutive behavior and elongation of alloy are inevitable during partial solidification. For predicting both the maximum true stress σ_ss and the elongation ε_elong regardless of alloy systems, their dominant factor was examined in terms of the solidification microstructure. For an Al-Mg and an Al-Cu alloys, (i) temperature T dependences of the maximum true stress and elongation (σ_ss=f(T) and ε_elong=f(T)) and (ii) dihedral angle θ of liquid phase formed at grain boundary were measured experimentally. Then, fraction of solid cohesion C was determined by the Campbells model using the angle. Firstly, the solid fraction dependence of the tensile properties (σ_ss=f(f_s) and ε_elong=f(f_s)) were compared between the two alloys. The two dependences differ with each other. Secondly, the fraction of solid cohesion dependences of the tensile properties (σ_ss=f(C) and ε_elong=f(C)) were compared and the result shows that the two dependences were consistent with each other. The fraction of solid cohesion enables to explain the difference in solid fraction dependence of the tensile properties for the two alloys. The result demonstrates that the dihedral angle should be essential to predict the two tensile properties of alloy during partial solidification.