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This study investigated the influence of the solid cohesion, f s c , on the viscous properties (m -value and k -value in the Norton law) for aluminum alloys during partial solidification. In the previous study of Haaften (Mater. Sci. Eng. A, 336 (2002), 1–6), a constitutive model taking into account f sc was proposed as ε ˙ = k (T) (σ / f sc (θ,T)) n (=1/ m), where θ referred to the dihedral angle at the solid/liquid interface. However, even though it is well known that the m -value decreases with the decreasing temperature in the semi-solid state, the model defined the m -value as a constant to the temperature. Therefore, m = f(f sc) and k = g(f sc) during solidification were clarified in this study. The viscous properties were obtained by tensile tests during partial solidification for Al-5mass%Mg and Al-2mass%Cu alloys. As a result, it was found that the change in the m -value of 0 ≤ f sc < f sc|eut.st was expressed by the following linear rule-of-mixtures: m = m solid (f sc / f sc|eut.st) + m liquid (1– f sc / f sc|eut.st), where f sc|eut.st is f sc at the beginning of the eutectic solidification, while m solid and m liquid are the m -values just below the solidus temperature and at f sc = 0, respectively. The increase in f sc due to the eutectic solidification hardly affected the change in the m -value and such a value was equivalent to m solid. On the contrary, the change in the k -values was found to obey the Arrhenius equation rather than be controlled by f sc. It is suggested that regardless of the aluminum alloy composition, the viscous properties of partial solidification can be determined using the these relationships. [ABSTRACT FROM AUTHOR]

This study investigated the influence of the solid cohesion, f s c , on the viscous properties (m -value and k -value in the Norton law) for aluminum alloys during partial solidification. In the previous study of Haaften (Mater. Sci. Eng. A, 336 (2002), 1–6), a constitutive model taking into account f sc was proposed as ε ˙ = k (T) (σ / f sc (θ,T)) n (=1/ m), where θ referred to the dihedral angle at the solid/liquid interface. However, even though it is well known that the m -value decreases with the decreasing temperature in the semi-solid state, the model defined the m -value as a constant to the temperature. Therefore, m = f(f sc) and k = g(f sc) during solidification were clarified in this study. The viscous properties were obtained by tensile tests during partial solidification for Al-5mass%Mg and Al-2mass%Cu alloys. As a result, it was found that the change in the m -value of 0 ≤ f sc < f sc|eut.st was expressed by the following linear rule-of-mixtures: m = m solid (f sc / f sc|eut.st) + m liquid (1– f sc / f sc|eut.st), where f sc|eut.st is f sc at the beginning of the eutectic solidification, while m solid and m liquid are the m -values just below the solidus temperature and at f sc = 0, respectively. The increase in f sc due to the eutectic solidification hardly affected the change in the m -value and such a value was equivalent to m solid. On the contrary, the change in the k -values was found to obey the Arrhenius equation rather than be controlled by f sc. It is suggested that regardless of the aluminum alloy composition, the viscous properties of partial solidification can be determined using the these relationships. [ABSTRACT FROM AUTHOR]