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.

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High-alloy cold rolled TRIP/TWIP steels have a remarkable potential for crash-relevant structures. Electron beam welding (EBW) can be regarded as being predestined for this purpose due to, among other factors, its locally limited heat input. The aim of this work is the characterization of the influence of the welding conditions on the chemical composition, the microstructure, and the mechanical properties of high-alloy cold rolled TRIP/TWIP steels. Three CrMnNi steels are cold rolled and welded with different beam intensities. The microstructure of the weld seams (WS) and the heat-affected zones (HAZs) is characterized by means of light microscopy and scanning electron microscopy (SEM). The mechanical properties of the welded joints are evaluated by hardness measurements and tensile testing. The weld seams are defect-free and surrounded by narrow HAZs. The microstructures inside the HAZs exhibited recrystallization and reverse annealing effects and constituted the failure-relevant area of the weld.

Due to their enormous potential for energy absorption, high-alloy TRIP/TWIP steels are designed to fulfill contrary requirements of crash-relevant structures such as strength, toughness, and ductility and even excellent weldability. To further optimize these mechanical properties and reduce the production costs at the same time, high-alloy TRIP/TWIP steels with an increased content of carbon and nitrogen and decreased amount of nickel are produced. The mechanical properties of the base materials and the capability for the phase transformation are determined for different temperatures (À40 to þ60 8C) in quasistatic tensile tests. In comparison, welding experiments with an electron beam are performed and the microstructure is examined via light optical microscopy. The welded sheets are also tested and the mechanical properties determined via micro-hardness measurements and quasistatic tensile tests. While a TRIP effect is noticeable during loading at room temperature, optimal properties of the base material can be achieved at temperatures below 0 8C. The welded samples show a ferritic-austenitic microstructure and solidified as primary ferritic with joint austenite and ferrite formation in the solidification interval.