Electron beam welding of Fe–Mn–Al–Ni shape memory alloy: Microstructure evolution and shape memory response

Abstract

The present study reports on the impact of abnormal grain growth (AGG) on the microstructural evolution following electron beam (EB) welding of Fe-Mn-Al-Ni shape memory alloy (SMA). Polycrystalline sheet-like material was EB-welded and a cyclic heat treatment, studied in previous work, was conducted for inducing AGG and a bamboo-like microstructure, respectively. Optical and electron microscopy were carried out to characterize the prevailing microstructure upon cyclic heat treatment. For characterization of the functional properties following AGG, a load increase test was conducted. The current results clearly show that good shape memory response can be obtained in Fe-Mn-Al-Ni SMA upon EB welding and subsequent post-heat treatment. These results further substantiate the potential use of conventional processing routes for Fe-Mn-Al-Ni SMA.

Welding characteristics and microstructure of an industrially processed Fe-Mn-Al-Ni shape memory alloy joined by tungsten inert gas welding

“…Figure 3) leads to a significant scattering of the hardness values across this zone. The average hardness of the FZ complies with the hardness of bamboo-like heat-treated specimens (in solutionized and quenched condition) reported by Krooß et al [27]. It should be noted that the hardness reported in that paper results from a pure α-matrix, whereas the hardness values of the FZ in Fig.…”

“…The hardness of the BM is similar to the value determined by Krooß et al for an alloy processed using laboratory equipment [27]. In Fig.…”

“…Therefore, several studies have already been devoted to the welding behaviour of Fe-SMAs. Various studies addressed laser welding and tungsten inert gas (TIG) welding of Fe-Mn-Si [25,26], as well as electron beam welding and induction butt welding of Fe-Mn-Al-Ni [27,28]. During induction butt welding of, the evolution of a large α-fraction in the fusion zone (FZ) is seen, while the γ-phase forms only along the grain boundaries and is more prominent in the heat affected zone (HAZ).…”

Laser welding of Cu-Al-Be shape memory alloys: Microstructure and mechanical properties

“…However, during the stress induced transformation it is possible that some grains exceed locally the stress for slip to occur [37], which will result in an irrecoverable strain upon unloading [38]. It must be pointed though, that these results are the best, in terms of superelastic recovery during mechanical cycling, for any welded shape memory alloy, when compared to the available literature on the subject [3,39,40].…”

Mechanical and Microstructural Characterization of Ultrasonic Welded NiTiCu Shape Memory Alloy Wires to Silver-Coated Copper Ferrules

“…To join SMAs with similar and dissimilar materials, fusion welding processes, such as tungsten inert gas welding [11,12] or electron beam welding [13,14], are often applied. Laser beam welding is used especially frequently because of the high welding speed and the minimal heat input.…”