1. Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 575-0871, Japan
2. Kawasaki Heavy Industries Ltd, 3-1-1, Higashikawasaki-cho, Chuo-ku, Kobe, Hyogo 650-8670, Japan
3. Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan