Al-5%Mg合金の高温脆化に及ぼす主として添加元素の影響

抄録

The ductility of Al-5wt%Mg alloy at elevated temperatures which was affected by a trace addition of Y, Ce, Sm and Be or by melting atmospheres was examined. Tensile tests in vacuum were made in a temperature range from 200°C to 400°C at a strain rate 8.3×10^-4s^-1, where the grain size of test pieces was controlled to be 0.35mm. Hightemperature embrittlement was clearly observed at about 300°C in the Al-Mg binary alloy prepared by melting in air in accord with the previous papers. However, the embrittlement almost disappeared by the addition of Y, Ce, Sm and Be when the alloy was prepared by melting in air. The phenomenon was attributed to the fact that formation and growth of cavities on grain boundaries were effectively checked, because strain-induced boundary migration easily occurred during tensile tests in those alloys. It was suggested that the high-temperature embrittlement so far reported was related to certain gas impurity atoms introduced in the course of melting in air. The impurity atoms would prevent the boundary migration. The additives would have a strong interaction with the impurity atoms above described.