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Publicação
Laser welding of H-phase strengthened Ni-rich NiTi-20Zr high temperature shape memory alloy
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Orientador(es)
Resumo(s)
Laser welding of a Ni-rich NiTi-20Zr (at.%) high temperature shape memory alloy was performed. The starting base material was aged for 3 h at 550 °C followed by air cooling prior to welding to induce H-phase precipitation. Advanced microstructure characterization encompassing scanning and transmission electron microscopy, coupled with synchrotron X-ray diffraction, were used. Defect-free welds were obtained with a conduction welding mode. The weld thermal cycle altered the microstructure across the heat affected and fusion zones of the joints. The heat affected zone exhibited partial H-phase dissolution, causing a decrease in hardness. In the fusion zone, the H-phase fully dissolved, and the non-equilibrium rapid solidification conditions prevented the H-phase from re-precipitating during cooling, leading to a microstructure resembling that of an as-cast alloy with the same material composition. Mechanical testing revealed that the laser welded samples sustained stresses in the order of 500 MPa and exhibited stress-strain responses comparable to those of the unwelded base material. Thus, this initial study shows new possibilities for using advanced laser joining methods in these alloys.
Descrição
proposal I-20160912
Palavras-chave
H-phase High temperature shape memory alloys Laser welding NiTiZr Rietveld refinement Synchrotron X-ray diffraction General Materials Science Mechanics of Materials Mechanical Engineering