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Correlation between the mechanical cycling behavior and microstructure in laser welded joints using NiTi memory shape alloys
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Resumo(s)
The demand of emerging joining techniques for shape memory alloys has become of great
importance, as their functional properties, namely shape memory effect and superelasticity, present unique solutions for state-of-the-art applications. Literature shows that significant efforts have been conducted on laser welding of these alloys, although very limited results
concerning mechanical properties are reported.
In this study, the main objective was to correlate the microstructure of similar NiTi welds with its mechanical behavior. A set of cycling tests was used in order to analyze the superelastic behavior of the welds. Also, shape memory effect was evaluated by means of a bending and free-recovery test. X-ray diffraction analysis allowed to identify the existing phases in the base
material, heat affected zone and fusion zone. SEM images of fracture surfaces were also analyzed.
It was observed the superelastic behavior of the welds during the mechanical tests. Also shape memory effect was shown to exist on welded samples even after cycling. X-ray diffraction showed a microstructural gradient across the samples. The welding parameters influence the mechanical behavior under cycling of the welds. In particular, there is a specific range of values of heat input introduced during welding that allow obtaining a good mechanical behavior under cycling of the welds.
Descrição
Dissertação para obtenção do Grau de Mestre em
Engenharia de Materiais
Palavras-chave
Shape memory alloys NiTi Laser welding Nd:YAG Superelasticity Shape memory effect