In this paper, the influences of build orientation and post-fabrication processes, including stress-relief, machining, and shot-peening, on the fatigue behavior of stainless steel (SS) 316L manufactured using selective laser melting (SLM) are studied. It was found that horizontally-built (XY) and machined (M) test pieces, which had not been previously studied in the literature, in both stress-relieved (SR) or non-stress-relieved (NSR) conditions show superior fatigue behavior compared to vertically-built (ZX) and conventionally-manufactured SS 316L. The XY, M, and SR (XY-M-SR) test pieces displayed fatigue behavior similar to the XY-M-NSR test pieces, implying that SR does not have a considerable effect on the fatigue behavior of XY and M test pieces. ZX-M-SR test pieces, due to their considerably lower ductility, exhibited significantly larger scatter and a lower fatigue strength compared to ZX-M-NSR samples. Shot-peening (SP) displayed a positive effect on improving the fatigue behavior of the ZX-NSR test pieces due to a compressive stress of 58 MPa induced on the surface of the test pieces. Fractography of the tensile and fatigue test pieces revealed a deeper understanding of the relationships between the process parameters, microstructure, and mechanical properties for SS 316L produced by laser systems. For example, fish-eye fracture pattern or spherical stair features were not previously observed or explained for cyclically-loaded SLM-printed parts in the literature. This study provides comprehensive insight into the anisotropy of the static and fatigue properties of SLM-printed parts, as well as the pre- and post-fabrication parameters that can be employed to improve the fatigue behavior of steel alloys manufactured using laser systems.

Theoretical and experimental methods are presented for the determination of creep isochronous loci of copper and aluminium alloy subjected to multiaxial stresses. Creep tests were carried out in a complex stress state at elevated temperature equal to 523 K in the case of copper and 423 K for aluminium alloy. Typical creep parameters, such as the duration of primary creep, the duration of secondary creep, the minimum creep rate and the time to rupture are analysed. The preliminary results for copper proved its isotropy during monotonic loading tests. In the case of creep conditions the material demonstrated anisotropic behaviour. A similar effect was observed for aluminium alloy; however, in this case the material exhibited additionally an initial anisotropy during monotonic loading tests. It is shown that for both materials, at the range of selected effective stresses, all typical creep parameters (e. g. minimum creep rate, time to rupture) are functions of the state of stress. The isochronous creep rupture surfaces were determined on the basis of experimental data and compared with those resulting from theoretical considerations. The surfaces describing the time to the end of primary creep and the start of tertiary creep are the same as the isochronous rupture surface. The latter is best described using the Sdobyrev equation with appropriate coefficients.

The paper presents experimental results of creep and low cycle fatigue (LCF) tests carried out on the as-received cast aluminium alloys with different chemical composition and porosity. The test programmes contain creep investigations under step-increased stresses at different temperatures, and cyclic plasticity under different strain amplitudes and temperatures.