Papers by Author: K. Shinozaki

Abstract: The microstructure, mechanical properties, hardness, rules and mechanism of various parameters on formation of weld bead of Mg alloy ACM522 using a fiber laser welding were investigated. The results showed that sound welds without major defects could be produced and the mechanical properties of welding joints were good. With the increase of laser power, the penetration depth and bead width of the weld bead all increased. The mechanism of welding transformed from the conduction welding mode to the deep penetration welding mode and the weld beads aspect ratio became higher with the increase of heat input. The microstructure of weld metal was significantly finer and the hardness of weld metal was higher than that of the base metal.

Abstract: Liquid Penetration Induced (LPI) cracking during AZ91, AZ31 and AM60 friction stir spot welding is investigated. The temperature cycles, within the stir zone and in the TMAZ region, are examined. The mechanism and the key factors determining LPI cracking in Mg-alloy friction stir spot welds are delineated.

Abstract: This study was carried out on the development of the evaluation method for solidification cracking susceptibility of Inconel600/SUS347 dissimilar weld metals during laser welding. Some dissimilar weld metals which have different ratios of Inconel600/SUS347 were prepared by TIG welding and then were remelted on the U-type hot cracking tester by laser. Solidification cracking behavior during hot cracking test was observed by a high speed camera and the dynamic strain, close to the solidification crack, was evaluated. It appeared that local critical strain, for the initiation of solidification crack, was obtained by this strain measurement method. So the solidification cracking susceptibility could be directly evaluated based on the critical strain for different dissimilar joint. By using this method, it was discovered that solidification cracking occurred most easily when the ratio of Inconel600/SUS347 is 40%/60%, in the case of the Inconel600/SUS347 dissimilar laser welded joints.

Abstract: Brazing of Al to Cu using Al-Si-Mg-Bi brazing alloy has been carried out in a vacuum furnace. In the brazed interlayer, there were two kinds of intermetallic compounds. One of these
intermetallic compounds was θ phase and the other was δ(Cu3Al2). Tensile strength of the joint was only about 15MPa. Deformation behavior of Al/Cu brazing joint was brittle without deformation of the base metal. The specimen was fractured in the intermetallic compound which was mainly θ phase. In order to improve the tensile strength of Al/Cu dissimilar joint, Cu cladding Ag (thickness: 0.1mm) substituted for Cu. As the result, tensile strength of the joint was about 70MPa and the specimen was fractured in an Al base metal. In this joint, plate-like intermetallic compound, δ (Ag2Al) was formed in the brazed interlayer. The shape of δ(Ag2Al) was quite different from θ phase found in Al/Cu joint. It was considered that the shape of reaction layer remarkably affected to the strength of the Al/Ag-Cu clad dissimilar joint.