Browsing by Author "Li, XP"

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    Fracture and fatigue behaviour of a laser additive manufactured Zr-based bulk metallic glass
    (Elsevier, 2020-12) Best, JP; Ostergaard, HE; Li, BS; Stolpe, M; Yang, F; Nomoto, K; Hasib, MT; Muránsky, O; Busch, R; Li, XP; Kruzic, JJ
    Laser additive manufacturing of bulk metallic glass (BMG) provides an effective bypassing of the critical casting thickness constraints that limit the size of components that can be produced; however, open questions remain regarding the resulting mechanical properties. In this work, a Zr-based BMG known as AMZ4 with composition Zr59.3Cu28.8Nb1.5Al10.4 was printed using a laser powder bed fusion (LPBF) technique. Micro X-ray computed tomography results together with electron microscopy imaging revealed porous processing defects in LPBF produced AMZ4 that led to a loss in tensile strength. Fatigue crack growth studies revealed a fatigue threshold, ΔKth., of ∼1.33 MPa√m and a Paris law exponent of m = 1.14, which are relatively low values for metallic materials. A KIC fracture toughness of 24−29 MPa√m was found for the LPBF BMG samples, which is much lower than the KQ of 97−138 MPa√m and KJIC of 158−253 MPa√m measured for the cast alloy with the same composition. The lower fracture toughness of the laser processed AMZ4 was attributed to ∼7.5× higher dissolved oxygen in the structure when compared to the cast AMZ4. Despite the higher level of oxygen, the formation of oxide nanocrystals was not observed by transmission electron microscopy. Oxygen induced toughness loss was confirmed by dissolving elevated concentrations of oxygen into cast AMZ4 rods, which led to a reduction in bending ductility and changes in the short-range order of the glass structure, as revealed by synchrotron X-ray diffraction. © 2020 Elsevier B.V.
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    Residual stresses in selective laser melted components of different geometries
    (Materials Research Forum LLC, 2016-07-03) Reid, M; Sercombe, T; Paradowska, AM; Li, XP
    As an emerging Additive Manufacturing (AM) technique, Selective Laser Melting (SLM) has found a promising application in biomedical field due to its advantages in fabricating Ti-6Al-4V components with specific and customised geometries. It has been reported that accumulated residual stress as a result of the high heating and cooling rates during SLM and the topological design of the components can largely influence the mechanical and functional properties of the fabricated components. In this study three notched samples were produced by SLM manufacturing. The samples were built using the same laser melting conditions on the same base size. The notches ranged in angle from 60° to 120°. Residual stresses in the three notched samples were analysed using the state-of-the-art neutron residual strain measurement instrument, Kowari, at the Australian Nuclear Science and Technology Organisation. A combination of gauge volumes were utilised to obtain high precision measurements at the notch tips and general measurements around the tips. This paper reports on the manufacture and measurement of differing residual stresses in the three SLM fabricated notches. © The Authors