Fiber laser welding of NiTi to Ti-6Al-4V

Abstract

Joining of multimaterials is a major issue for several industrial applications where the combination of individual material properties increases component performance. The objective of this experimental study is to assess the laser weldability of NiTi to Ti-6Al-4V. Dissimilar welds were performed on 1-mm-thick plates with a high-power fiber laser with different heat inputs to control the cooling rate. Fracture was always observed in the weld metal in a solidification cracking phenomena. Scanning electron microscopy with EDS was performed to analyze the fracture surfaces. Solidification cracking was observed in the fusion zone associated to Ti 2 Ni formation in two distinct fracture morphologies: brittle transgranular cracking in the Ti 2 Ni regions and dimple intergranular failure along the solidification dendrites. Thus, autogeneous welding of these two materials is difficult due to intermetallics formation and filler materials or interlayers are needed to prevent the formation of brittle intermetallics.

Laser joining of NiTi to Ti6Al4V using a Niobium interlayer

“…Preliminary welding tests were performed without filler material to determine the welding power intensity required. As expected from previous work [9], cracking upon solidification occurred due to the formation of brittle intermetallics and residual thermal stresses. In order to overcome the solidification cracking, a Niobium interlayer was introduced between the materials as a diffusion barrier.…”

Welding and Joining of NiTi Shape Memory Alloys: A Review

“…Assessment of the weldability of NiTi to Ti6Al4V was investigated by Miranda et al [182]. Regardless of the heat input introduced during welding, to control the cooling rate upon solidification, cracking was always observed in the FZ.…”

Interaction between Ni/Ti Nanomultilayers and Bulk Ti-6Al-4V during Heat Treatment

“…In particular, dissimilar joining can be challenging and often a filler material is required. Several joining attempts have been made by laser welding [3][4][5], brazing [6,7] and diffusion bonding [8][9][10]. Regarding the dissimilar diffusion bonding of Ti-6Al-4V, it is common to introduce metal foils as intermediate material [11].…”