| Summary: | 碩士 === 國立臺灣師範大學 === 機電科技研究所 === 97 === The purpose of this study is to investigate the plasma arc welding properties of the zircaloy R60702 thin 2mm by using the tensile test（including force, elongation, engineering stress and engineering strain）, the micro-hardness, the optical microscopy（base metal, hot affect zone and fusion zone）and scanning electron microscopy（ductile or brittle fracture）.
Based on the experimental results, all of the tensile specimens ruptured in the base metal. Bonding strength of fusion zone was higher than that of base metal. In addition, the tensile strength, yield strength, elongation and hardness of the zircaloy R60702 sheet before welding was 497.95 MPa, 322.10 MPa, 38.40%, Hv161, respectively. After welding, the tensile strength and elongation of weld were 484.22 MPa and 24.40%, respectively. The tensile strength of the welding region was about 90% of the base metal. Thus, the yielding strength will be higher than base metal, while the percentage elongation will be lower than base metal. From the microstructure observation, the surface of fusion zone was all columnar dendritic. The center of fusion zone tends to basket weave. The fracture surface of tensile test specimens has the feature of dimple.
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