Browsing by Author "Yadroitsev, I."

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    Influence of process parameters on residual stress related distortions in selective laser melting
    (Elsevier, 2018) Mugwagwa, L.; Dimitrov, D.; Matope, S.; Yadroitsev, I.
    ENGLISH ABSTRACT: Residual stresses pose a major setback in Selective Laser Melting (SLM) and limit the applicability of the process, particularly from the standpoint of form accuracy and mechanical strength. The purpose of this paper is to investigate the influence of SLM parameters namely laser power and scanning speed on thermal stress related warping distortions and porosity. In this study, residual stress related distortions and achievable density for different process parameter combinations are presented simultaneously due to the profound influence of the porosity on residual stress relaxation. The paper also discusses the implications of the process parameters on the sustainability of the SLM process.
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    Manufacturing and characterization of in-situ alloyed Ti6Al4V(ELI)-3 at.% Cu by laser powder bed fusion
    (Elsevier, 2020) Vilardell, A. M.; Yadroitsev, I.; Yadroitsava, I.; Albu, M.; Takata, N.; Kobashi, M.; Krakhmalev, P.; Kouprianoff, D.; Kothleitne, G.; Du Plessis, A.
    Biofunctionalization of Ti6Al4V alloy with metallic agents like Ag or Cu is a promising approach to add anti-bacterial properties and thus to reduce the risk of implant failure. This research investigates the in-situ alloying of Ti6Al4V(ELI) with 3 at.% Cu powders using Laser Powder Bed Fusion (L-PBF). The morphology and geometrical characteristics of the single tracks and layers were studied. Laser powers of 170 W and 340 W, and scanning speeds ranging from 0.4 to 1.4 m/s and 0.8–2.8 m/s were implemented. Single track results showed balling effect and humping at high scanning speeds, 1.4 m/s and 1.6 m/s, for each laser powder respectively. Conversely, keyhole formation occurred at lower scanning speeds of 0.4–0.6 m/s for 170 W laser power, and below and 0.8 m/s for 340 W laser power. For both laser powers, single layers resulted in smoother surfaces at lower scanning speeds. These results were used for the development of optimal process parameters for 3D cubes with 99.9 % density. Optimal process parameters were found for 170 W and 340 W laser powders at 0.7−0.9 and 1.0–1.2 m/s scanning speeds, respectively. In-situ alloying by L-PBF was challenging and a homogeneous distribution of Cu within the alloy was hard to achieve. The increase in laser power from 170 to 340 W resulted in small increase in homogenization. Microstructural analyses after stress-relieving treatment showed the presence of α’ and β phases, as well as CuTi₂ intermetallic precipitates. The finer microstructure together with CuTi₂ intermetallic precipitates resulted in an increase in hardness. This study demonstrates the potential for printing in-situ alloyed Ti6Al4V(ELI)- 3 at.% Cu for biomedical applications. However, further studies are required to determine the effectiveness of antibacterial properties.
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    Tensile properties and microstructure of direct metal laser-sintered TI6AL4V (ElI) alloy
    (Southern African Institute for Industrial Engineering, 2016) Moletsane, M. G.; Krakhmalev, Pavel; Kazantseva, N.; Du Plessis, Anton; Yadroitsava, I.; Yadroitsev, I.
    ENGLISH ABSTRACT: Direct metal laser sintering (DMLS) is an additive manufacturing technology used to melt metal powder by high laser power to produce customised parts, light-weight structures, or other complex objects. During DMLS, powder is melted and solidified track-by-track and layer-by-layer; thus, building direction can influence the mechanical properties of DMLS parts. The mechanical properties and microstructure of material produced by DMLS can depend on the powder properties, process parameters, scanning strategy, and building geometry. In this study, the microstructure, tensile properties, and porosity of DMLS Ti6Al4V (ELI) horizontal samples were analysed. Defect analysis by CT scans in pre-strained samples was used to detect the crack formation mechanism during tensile testing of as-built and heat-treated samples. The mechanical properties of the samples before and after stress relieving are discussed.