Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5017998 | Journal of Materials Processing Technology | 2017 | 18 Pages |
Abstract
Tensile test showed that the strength of the welded joints of powder metallurgy Ti-51%atNi shape-memory alloys (SMAs) decreases after disk-laser welding due to the presence of pores and columnar structure in the fusion zone. There was a reduction in the superelastic behavior of the welded joints compared to the base metal. Superelastic properties of specimen LW1 (with welding speed of 6 m/min and laser power input of 3 kW) were close to the base metal after loading and unloading at room temperature. Welded specimens, which were subjected to solution treatment at 1000 °C followed by aging at 500 °C showed an increment in superelasticity properties. Superelasticity improved significantly after heat treatment in all the welded joints except LW2 (with welding speed of 7.5 m/min and laser power input of 3 kW), because it contained high amounts of porosity in the fusion zone. LW1 exhibited the best properties after heat treatment with superelasticity strain increasing up to 7%, which was higher than the base metal. Differential scanning calorimetry (DSC) investigations showed that heat-treated weld seams had similar phase transformation peaks of martensite, austenite, and R phases to the base metal, which may be due to the recovering of Ti3Ni4 precipitates.
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Authors
Abdollah Bahador, Esah Hamzah, Katsuyoshi Kondoh, Yousuke Kawahito, Umeda Junko, Tuty Asma Abu Bakar,