The welding characteristics of Fe–30Mn–6Si and Fe–30Mn–6Si–5Cr shape memory alloys

• Published in: Journal of alloys and compounds 2000-06, Vol.306 (1), p.186-192
• Main Authors: Lin, H.C., Lin, K.M., Chuang, Y.C., Chou, T.S.
• Format: Article
• Language: English
• Subjects: Fe-based shape memory alloys; Laser welding; Tungsten-inert gas welding
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/S0925-8388(00)00762-3

After tungsten-inert gas (TIG) and laser welding, the microstructure, shape memory effect and chemical corrosion resistance of Fe–30Mn–6Si and Fe–30Mn–6Si–5Cr shape memory alloys have been investigated. Experimental results show that the dendrite structures in the laser-welded zones are finer than in the TIG-welded zones for both Fe–30Mn–6Si and Fe–30Mn–6Si–5Cr specimens. The Mn content in the TIG-welded zone of Fe–30Mn–6Si specimen is obviously reduced due to its vaporization during welding. The as-welded alloys still exhibit an excellent shape memory effect, with a variation of ±10% due to welding. The corrosion resistance of welded zones is worse than that of base material for both Fe–30Mn–6Si and Fe–30Mn–6Si–5Cr specimens. The degradation of corrosion resistance is ascribed to the micro-segregation and welding stress occurring within the welded zones. Meanwhile, the Cl − is more corrosive than the NO 3 − for Fe–Mn–Si shape memory alloys. After annealing treatment of 1100°C×2 h for these welded alloys, the dendrite structures in the welded zones disappear. The welded-then-annealed Fe–Mn–Si specimens still maintain the excellent shape memory effect, and their corrosion resistance is improved due to the annihilation of micro-segregation and welding stress.