Mechanical Properties Study of Fe-Mn-Si Shape Memory Alloys Welding Seam Formed by Laser Welding with Filler Powder

Abstract

To reduce the residual stress and improve the fatigue property of the laser weldment by using the stress self-accommodation characteristic of Fe-Mn-Si shape memory alloys (SMAs), a Fe15Mn5Si12Cr6Ni memory alloy welding seam was formed inside 304 stainless steel by laser welding with filler powder. The combination of the hole-drilling method and the ANSYS software was used to research the distribution law of residual stress inside the laser welding specimen. The fatigue strength of the laser welded specimens with the Fe-Mn-Si SMAs welding seam (experimental materials) and 304 stainless steel welding seam (comparative materials) was measured by cycle bending fatigue test. The microhardness of the welding specimens was measured by the microhardness tester. The thermodynamic model of the laser welding process and the phase transition crystallography of Fe-Mn-Si SMAs were evaluated to analyze the strengthening mechanism of the mechanical properties in the experimental materials. The results show that the distribution law for residual stress in the experiment and simulation are consistent. The experimental materials possess low residual stress, high fatigue strength and high microhardness. The strengthening mechanism for mechanical properties is the welding residual stress-induced γ→ε martensitic transformation inside the experimental materials, which causes the tensile plastic strain of the welding seam to resist residual compression strain, and the residual stress, as the transition driving force, is released in shear processing.

Effect of PZT doping amount on microstructure and properties of Fe-based memory alloy composite coating by laser cladding

“…The memory mechanism of Fe-Mn-Si shape memory alloys originates from thermally or stress-induced γ ↔ ε martensite transformation and its inverse transformation [16]. Ju [17] found that the characteristic of stress self-accommodation of Fe-Mn-Si shape memory alloy can effectively reduce the residual stress generated by laser welding and has excellent mechanical properties. Xu [18] successfully prepared a Fe-Mn-Si(SMA) coating on the surface of 304 stainless steel, which has the characteristic of stress self-accommodation.…”

Distribution of Al Element of Ti–6Al–4V Joints by Fiber Laser Welding

“…At present, the problem of elemental evaporation loss is solved industrially by increasing the content of low-boiling-point elements in the wire or powder feedstock or appropriately reducing the laser power. However, after the filling material enters the molten pool, the distribution of the filling elements in the weld may also have some unevenness due to the convection and agitation of the molten pool, which will affect the performance of the welded joint [10,11].…”