抄録
The mechanism of the crystal structure transformation of Al3Ti from DO22 to a high symmetry Ll2 by the addition of Cu was investigated using the DV-X α molecular orbital calculation. The calculation suggested that Ti atoms were able to locate at the 2nd neighbor sites of Ti atoms by substitution of Cu atoms for a part of Al atoms, namely, the 1st neighbor sites of Ti atoms. This atomic configuration is the mechanism for the stabilization of the Ll2 crystal structure of Al3Ti by the addition of Cu. Therefore, Cu was added to improve the ductility of a new reaction sintered Al-Ti-N alloy which consists of Al3Ti and AlN phases. The added Cu transformed the crystal structure of Al3Ti from DO22 to a high symmetry Ll2, and as a result, decreased the hardness of the alloy.
