Microstructural Characterisations of Welded Shape Memory Alloys

Year 2019, Volume: 15 Issue: 4, 415 - 421, 30.12.2019

Halit Doğan , Nevzat Sarı

https://doi.org/10.18466/cbayarfbe.497388

Abstract

Today, with
the development of technology, different welding methods are applied for
different alloys. In this work, changing of functional properties after using
welding methods for NiTi alloy samples was targeted. However, two different
welding methods were employed for the same alloy and results were compared to
each other and commented on them. In the present study, samples were welded
with TIG and Laser welding and their cross section was examined in the joint
area. Then these samples were examined in optical microscope and SEM. The
advantages and disadvantages of both welding methods were reported. The basic distinction
of TIG and laser welded samples examined in microscope was the scale of HAZ
area of TIG welded piece. Nevertheless, due to more thermal input is applied
for materials in TIG welded parts, more molten materials are detected or heat
effects are attained in this practice. In laser welding, heat input is less and
this can be recognized from the observed micrographs. While HAZ area is obviously
distinguished and welding border zone is detached from the base metal. The twin
structures were not observed in optical microscope; for that reason they were
investigated in SEM to see these twins in laser welded area. 

Keywords

NiTi, Shape Memory Alloy, Superelastic, Twinning

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