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The present work explores the possibility of processing a CoCuFeMnNiTi0.13 high-entropy alloy by laser powder bed fusion (LPBF). The alloy, produced under optimised processing conditions, presents good densification but also hot cracks, caused by the liquation of an inter-dendritic Cu-rich phase. Microstructure of the as-built alloy is characterised by face centred cubic (FCC) columnar grains, containing Cu-poor dendrites and Cu-rich inter-dendritic areas. The alloy, which was designed to be strengthened by spinodal decomposition and precipitation, was subjected to different thermo-mechanical treatments to try and improve its properties. Direct ageing and solution treatment and ageing produced a strong but brittle material (tensile strength of 683 MPa and elongation to failure of 1.3%), whereas hot isostatic pressing followed by controlled cooling was able to heal pores and cracks while triggering the desired microstructural transformations (spinodal decomposition and precipitation). This resulted into a balanced set of mechanical properties (tensile strength of 473 MPa and elongation to failure of 7.6%). This work shows that proper post-processing can mitigate the issues typically affecting LPBF fabricated HEAs, producing tailored microstructures with satisfactory mechanical performances.

Since several years the need for realizing small and smart devices composed of functional materials is constantly increasing. Among this advanced materials, shape memory alloys (SMAs) are some of the most important functional materials in several applications, including in the biomedical and aerospace fields. Nowadays, laser cutting is probably the most widespread cutting technology for realising SMA mini- and micro-devices for several applications. The present manuscript reviews the scientific literature on the performance of laser-cut elements, in NiTi SMA, under different points of view. The literature was systematically analysed, according with a technological, metallurgical, functional and device/prototypal approaches. It can be highlighted that a relevant correlation between design, process condition and material performances can promote the realization of advanced smart devices made in NiTi SMA.

The present work aims at exploring the influence of laser welding on the functional behaviour of a Fe-20Mn-0.6C (wt.%) bioabsorbable alloy. At first, the selection of the most suitable process speed (40 mm/s) was done in order to obtain a full penetration joint with limited taper. Then, microstructural and mechanical analyses of welded sheets confirmed suitable performance of the joint, without porosity, thus preserving chemical composition, mechanical resistance and ductility even after welding. In particular, the base material comprised both γ austenite and ε martensite, while the welded samples showed a further type of martensite, namely α’. Moreover, ultimate tensile strength (1095 MPa and 1104 MPa in base and welded material, respectively) and elongation to failure (61.3% and 60.9%, respectively) were almost not influenced by the welding process. Considering the absorbable nature of these alloys, static immersion degradation tests were carried out, and confirmed that the surface of the welded bead did not exhibit a significant variation of the material degradation rate after 14 days in modified Hanks’ solution. Finally, a significant accumulation of degradation products, mainly (Fe,Mn)CO3, was observed along the joining line.