高周波誘導加熱引張試験による半凝固状態のAl-5mass%Mg合金の粘性特性の取得

抄録

To predict hot tearing during DC (direct chill) casting by thermal stress analysis, cooling rate dependence of viscous properties in semi-solid state are indispensable. However, those at cooling rates of DC casting had not been obtained in the past. In this study, a tensile test device with high frequency induction heating that can control the cooling rate was developed. By using this device, the viscous properties were obtained on Al-5mass%Mg alloy at 1 K/s and 5 K/s. To determine those, two methods were employed. The first method was to determine those from relationships between the maximum true stress, σ_max and the true strain rate, έ_max. The method suggested by Matsushita was employed as the second method. It was found that the viscous properties obtained by each methods were different at 1 K/s. This should be because the true strain rate was increased due to the formation of micro-damage inside the test piece at σ_max. The viscous properties of those that did not experience micro-damage were independent of the cooling rate. This should be because the degree of microsegregation was similar at the two cooling rates resulting in no difference in solid fractions.