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Titanium and titanium alloys with open cellular structures and foams possess low Young's modulus matching to human bone and the capability to provide space for bone tissue ingrowth to reach a better fixation, which have been thought as a good choice for the replacement of commercial dense implants. However, currently developed fabrication methods of titanium cellular alloys, such as powder sintering, reveal shortcomings like the low porosity and poor control over the size, shape and distribution of the pores. Recently, additive manufacturing using the electron beam melting method has been applied successfully to fabricate titanium cellular meshes and foams. Compared to other reported methods, this technique has the advantages of accurate control of internal pore architectures and complex cell shapes. In the present paper, the authors briefly review the fabrication, Young's modulus, mechanical properties and biocompatibility of Ti–6Al–4V cellular structures fabricated by electron beam melting techniques, along with future development trends. [ABSTRACT FROM AUTHOR]

Phase transformations and mechanical properties of both Ti–29Nb–13Ta–4·6Zr and Ti–39Nb–13Ta–4·6Zr (wt–%) alloys were investigated. The microstructure of the 29Nb alloy is sensitive to solution and aging treatment. Ice water quenching from the solution treatment temperature resulted in (β+α") microstructure but air or furnace cooling led to a mixture of (β+ω). The formation of the orthorhombic α" martensite thus suppresses ω formation in the ice water quenched 29Nb alloy. Cooling rate from the solution treatment temperature also has a significant effect on the formation of α and ω phases during subsequent isothermal aging below the ω start temperature: slow cooling enhances ω but depresses α formation. This cooling rate dependence of aged microstructure was attributed to α" martensite acting as precursor of the α phase, thus providing a low energy path to the precipitation of a at the expense of ω. Phase transformation in the 39Nb alloy is more sluggish than that in the 29Nb alloy, owing to the presence of the higher content of β stabiliser Nb. For the 29Nb alloy, Young's modulus and mechanical properties are sensitive to the fraction of phases, and change significantly during aging, in contrast with the 39Nb alloy. [ABSTRACT FROM AUTHOR]