Production and characterisation of mechanical properties of Ti–Nb–Ta–Mn alloys foams for biomedical applications C. Guerra 1 , C. Aguilar* 1 , D. Guzma ´n 2 , M. Arancibia 1 , P. A. Rojas 3 , S. Lascano 4 and L. Perez 4 Development of titanium foams with low Young’s modulus as a potential implant material has attracted significant attention. In this work, the effect of manganese on the mechanical properties in compression of Ti–13Ta– 30Nb–xMn foams (x52–6 wt-%) has been studied. Titanium based alloys produced by mechanical alloying were processed to obtain foams using ammonium hydrogen carbonate with a mean particle size of 35 mm (50% v/v) as a space-holder. Powders and space- holder were mixed and uniaxially pressed to form compacts. The space holder was removed by heating the green compacts to 180uC for 1 . 5h before sintering at 1300uC for 4 h in Ar. The Young’s modulus of the foam was lower than that of pure Ti, and the yield strength increased with the Mn addition. The Gibson–Ashby, Meyer and Nielsen models were applied to predict the mechanical properties of the titanium foams. As the average age and life expectancy of human beings has increased, degenerative diseases that lead to a decline in the mechanical properties of bone have become more common. It has been estimated that 90% of the population (over 40 year old) suffers from these diseases. Geetha et al. 1 predicted in 2009 that the total number of joint replacements in the USA will rise by 174% and the number of total knee arthoplasties by 673% by 2030, which would involve about 4 million surgeries. The USA already spends about US$254bn annually to treat musculoskeletal problems, according to data obtained from the American Academy of Orthopaedic Surgeons. 1 Artificial biomaterials are one solution to these problems and implants are expected to serve for extended periods without failure. Therefore it is important to develop appropriate materials with high longevity, adequate mechanical properties and excellent biocompatibility. Metallic materials are widely used as implants under load-bearing conditions. 2,3 The most commonly used materials for surgical implants are 316L stainless steels, Co–Cr alloys, Co– Cr–Mo alloys, pure Ti and Ti-based alloys. The 316L stainless steels, Co–Cr and Co–Cr–Mo alloys have the disadvantage of high elastic moduli E (y200 GPa, compared with 2–30 GPa for bone). 1,4 Ti and its alloys have been widely employed in biomedical applications because of their relatively low modulus, low density, high specific strength, biocompatibility and corrosion resistance. The first generation of Ti alloys had disadvantages such as relatively poor wear resistance, low hardness, 5,6 and high stiffness relative to human bone. This stiffness mismatch can lead to bone resorption and eventual loosening of the implant. 2,3 Also, the alloying elements present in Ti biomedical alloys (e.g. Al, V, Ni and Co) may have toxic effects when released into the human body, inducing dermatitis, alzheimer, neuropathy and ostemomalacia. 7–9 The second generation of Ti-based alloys employed non-toxic elements such as Nb, Mo, Zr, Ta and Mn, 10 but problems remain with the mechanical, stiffness and corrosion properties of these alloys. It has been reported that Mn has a special role as a co-factor in the formation of bone cartilage, bone collagen and bone mineralisation, 11 but although Ti–Mn alloys have been used in aerospace they have yet to be used in biomedicine applications. Nicula et al. 12 reported that the incorporation of Mn in Ti–Al–V could enhance cell adhesion. Few research studies have been published on the effect of Mn on Ti-based alloys, especially on second generation alloys such as Ti–13Nb– 13Zr, Ti–35Nb–7Zr–5Ta, Ti–Mo or Ti– 29–Nb–13Ta–4 . 6Zr. 1 Ti-based biomedical alloys are usually fabricated by casting and forging techniques, 13 but the use of high vacuum furnaces is required to prevent oxidation at temperatures above 800uC at which the alloys become highly reactive, and forging temperatures must be ,800uC for the same reason. It is also difficult to obtain nanocrystalline materials by this process route. One way to obtain alloys with lower elastic moduli is to use metallic foams, 14 but Ti-based foams are difficult to produce by a liquid metallurgy route due to the high melting point and high reactivity of the alloys. 15 Synthesis of Ti-based alloy foam by a powder metallurgy route is therefore attractive. The use of space holders as a means of tailoring the morphology and properties, particularly stiffness, of titanium foams produced by the PM route has attracted significant recent interest. 16–20 In this approach, organic 21 metallic 22 or inorganic 23,24 particles mixed with the metal powders are leached out 25 or burnt off in a pre-sintering step to produce pores of the required size and morphology. The objective of the present this work was to study the effect of Mn on the mechanical properties of Ti–30Nb–13Ta–xMn alloy foams (x52, 4 and 6%; all compositions in wt-%). Powder Metallurgy pomFE_Aguilar.3d 21/11/14 16:11:05 1 Departamento de Ingenierı ´a Metalu ´ rgica y Materiales, Universidad Te ´ cnicas Federico Santa Marı ´a, Av. Espan ˜ a 1680, Valparaı ´so, Chile 2 Departamento de Metalurgia, Universidad de Atacama, Av. Espan ˜ a 485, Copiapo ´ , Chile 3 Escuela de Ingenierı ´a Meca ´ nica, Facultad de Ingenierı ´a, Pontificia Universidad Cato ´lica de Valparaı ´so, Av. Los Carrera 01567, Quilpue ´, Chile 4 Departamento de Ingenierı ´a Meca ´ nica, Universidad Te ´ cnicas Federico Santa Marı ´a, Av. Espan ˜ a 1680, Valparaı ´so, Chile *Corresponding author, email claudio.aguilar@usm.cl ß 2014 Institute of Materials, Minerals and Mining Published by Maney on behalf of the Institute DOI 10.1179/0032589914Z.000000000211 Powder Metallurgy 2014 VOL 57 NO 5 1