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Publisher: Amsterdam : Elsevier B.V. × Subject: Titanium alloys ×

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    Mechanical performance and corrosion behaviour of Zr-based bulk metallic glass produced by selective laser melting
    (Amsterdam : Elsevier B.V., 2020) Deng, L.; Gebert, A.; Zhang, L.; Chen, H.Y.; Gu, D.D.; Kühn, U.; Zimmermann, M.; Kosiba, K.; Pauly, S.
    Nearly fully dense, glassy Zr52.5Cu17.9Ni14.6Al10Ti5 bulk specimens were fabricated by selective laser melting (SLM) and their behaviour during compressive loading, during wear testing and in a corrosive medium was investigated. Their performance was compared with as-cast material of the same composition. The additively manufactured samples exhibit a yield strength around 1700 MPa combined with a plastic strain of about 0.5% after yielding despite the residual porosity of 1.3%, which is distributed uniformly in the samples. The propagation of shear bands in the bulk metallic glass prepared by SLM was studied. The specific wear rate and the worn surfaces demonstrated that similar wear mechanisms are active in the SLM and the as-cast samples. Hence, manufacturing the glass in layers does not adversely affect the wear properties. The same holds for the corrosion tests, which were carried out in 0.01 M Na2SO4 and 0.1 M NaCl electrolyte. The anodic polarization curves of SLM samples and as-cast samples revealed a similar corrosion behaviour. However, the SLM samples have a slightly reduced susceptibility to pitting corrosion and exhibit an improved surface healing ability, which might be attributed to an improved homogeneity of the additively manufactured glass.
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    Microstructure and elastic deformation behavior of β-type Ti-29Nb-13Ta-4.6Zr with promising mechanical properties for stent applications
    (Amsterdam : Elsevier B.V., 2019) Plaine, A.H.; Silva, M.R.D.; Bolfarini, C.
    In this paper, an attempt was made to combine theoretical composition design and thermo-mechanical treatments to produce a metastable β-type titanium alloy with mechanical compatibility for self-expandable stent applications. Metastable β-type Ti-29Nb-13Ta-4.6â»Zr (wt.%) thin-wires with an elastic modulus of 46â»GPa and a yield strength of 920â»MPa were successfully fabricated by cold rolling and low temperature aging. This combination of high yield strength and comparatively low elastic modulus resulted in enhanced elastic recoverable strain of 1.9%, which is much higher than that of the conventional metallic stent materials. The microstructure responsible for the much sought-after mechanical properties was observed to be mainly consisted of a homogeneous distribution of nanometer-sized α-precipitates in a β-phase matrix obtained via a spinodal decomposition of the pre-existed α″-martensite phase through α″â»→â»α″ leanâ»+â»α″ richâ»→â»αâ»+â»β. The α-precipitates increase the strength of the material by hindering the motion of dislocations (spinodal hardening) while the β-matrix with relatively low content of β-stabilizers gives rise to the observed low elastic modulus. More broadly, these findings could be extended to developing advanced metastable β-type titanium alloys for implant and other engineering applications.