Asadi Saeed, Saeid Tohid, Valanezhad Alireza, Watanabe Ikuya, Khalil-Allafi Jafar
Faculty of Materials Engineering, Sahand University of Technology, Tabriz, Iran.
Department of Dental and Biomedical Materials Science, Nagasaki University, Nagasaki, Japan.
J Mech Behav Biomed Mater. 2020 Sep;109:103818. doi: 10.1016/j.jmbbm.2020.103818. Epub 2020 Apr 25.
Annealing after welding is a common operational process to improve the mechanical properties of metallic joints through releasing residual stresses in the weld zone. In this study, the effect of post weld annealing on the microstructure and mechanical properties of dissimilar laser-welds for orthodontic archwires of NiTi alloy to austenitic stainless steel has been investigated. In order to do this, the laser-welded wires were annealed at temperatures of 100, 200, and 300 °C for 1 h and then they were quenched in water. Results show that annealing at 100 °C does not affect the microstructure and mechanical properties of joints but post weld heat treatment at 200 °C ends in an increase in the tensile strength to an order of 1.91 times of the strength of as welded (non-heat-treated) joints. Also, precipitation and increase of intermetallic compounds, such as CrTi, and FeTi, at the weld zone during heat treatment at 300 °C, results in a reduction in the mechanical properties of joints. Therefore, post-weld annealing is an effective process on improving mechanical properties of dissimilar joints of these two alloys. However, a suitable heat-treatment temperature is needed in order to achieve desired results.
焊接后的退火是一种常见的操作工艺，通过释放焊接区域的残余应力来改善金属接头的机械性能。在本研究中，研究了焊后退火对镍钛合金正畸弓丝与奥氏体不锈钢异种激光焊接接头的微观结构和机械性能的影响。为此，将激光焊接的线材在100、200和300°C的温度下退火1小时，然后在水中淬火。结果表明，100°C退火不影响接头的微观结构和机械性能，但200°C的焊后热处理使拉伸强度提高到焊接（未热处理）接头强度的1.91倍。此外，在300°C热处理期间，焊接区域金属间化合物如CrTi和FeTi的析出和增加导致接头机械性能下降。因此，焊后退火是改善这两种合金异种接头机械性能的有效工艺。然而，为了获得理想的结果，需要合适的热处理温度。
