Evaluation of Cyclic Deformation Behavior of Laser-welded Shape Memory NiTi Alloys at Different Working Temperatures

Chi Wai Chan, H.C. Man

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Abstract

Post-weld heat-treatment (PWHT) has been established as one of the cost-effective ways to improve the functional properties, namely shape memory and super-elastic effects (SME and SE), of laser-welded NiTi alloys. However, the functional performance of the laser-welded joint at different working temperatures has not been explored yet. The purpose of this study is to investigate the effect of different working temperatures on the functional properties of the laser-welded NiTi alloys before and after PWHT by applying cyclic deformation tests. Two laser-welded samples: as-welded and heat-treated sample (after PWHT at 350 oC or 623 K) were tested in this work at room temperature, 50 oC (or 323 K) and 75 oC (or 348 K) respectively. The samples were cyclically loaded and unloaded for 10 cycles up to 4 % strain. The critical stress to induce the martensitic transformation and the residual strain after the cyclic tests were recorded. The results indicate that the heat-treated sample exhibited better functional properties than the as-welded sample at room temperature and 50 oC (or 323 K). However, both the as-welded and heat-treated samples failed in the cyclic tests at 75 oC (or 348 K). These findings are important to determine the feasible working temperature range for the laser-welded NiTi components to exhibit desirable functional properties in engineering applications involving cyclic loading.
Original languageEnglish
Number of pages6
Publication statusPublished - 21 Oct 2014
EventThe 33rd International Congress on Applications of Lasers & Electro-Optics (ICALEO®) - San Diego, CA, USA, San Diego, United States
Duration: 19 Oct 201423 Oct 2014

Conference

ConferenceThe 33rd International Congress on Applications of Lasers & Electro-Optics (ICALEO®)
CountryUnited States
CitySan Diego
Period19/10/201423/10/2014

Keywords

  • Laser Welding, Shape Memory Alloys, Post-weld Heat-treatment, Cyclic Deformation Behaviour

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