Development of the Open-Cell Toxic-Element-Free Ti-Based Bulk Metallic Glass Foams(3/3)

In this decade, metallic materials have been rapidly developed for the biomedical purpose after thediscovery of good biocompatibility on the Ti metal. The most popular applications of the Ti alloys (e.g. pure(cp) Ti, Ti-6Al-4V and Ti-6Al-7Nb) as biomedical implant materials is in the field of trauma and orthopedicsurgery. Recently, several novel Ti-based metallic glasses (Ti-MGs) with superior biomedical propertiescompared to its crystalline material counterpart has also been developed. These Ti-MGs have no crystalstructural defects (such as dislocations, grain boundaries or twins), homogenous chemical composition, higherstrength, lower Young’s modulus, and much better corrosion resistance. Although the Ti-MGs present betterbiomedical properties than the crystalline Ti alloys. However, based on the long-term durability and healthconcerns, two serious problems still exist in the above-mentioned two kinds of Ti-based materials. Theproblems are (1) The mismatch of the Young’s modulus (E) between the bone (E=10~30 GPa for corticalbone) and the implant (E=110~120 GPa for Ti-6Al-4V alloys, 80~90 GPa for Ti-MG). Large modulusmismatch will cause stress-shielding on the bone nearby the implant and induced tissue loss and increasingrecovery time. (2) The release of toxic metallic ions and/or particles through corrosion and wear processes.Some harmful elements are frequently added in the Ti alloy systems in order to improve mechanical propertiesand glass-form ability (GFA) (Al, V for Ti-6Al-4V alloys, Ni, Cu for Ti-MG). Accordingly, in this study, weare going to design a series of toxic-element-free Ti-Zr-(Ta, Nb)-(Sn, Co)-(Si, B, P) metallic glasses possesshigh GFA, wide supercooled temperature (SCL), high strength, and superior corrosion resistance. Then theTi-MGs will be fabricated into a bulk metallic glass foam (BMGF) by hot pressing within its SCL region, andto fit the requirement of human bone on the strength, Young’s modulus, and the pore size for bone cell growth.In the 1styear, one set of arc-melting and water-cooled melt-spinning equipment will be established andset up to design the high GFA of toxic-element-free Ti-Zr-(Ta, Nb)-(Sn, Co)-(Si, B, P) metallic glasses, andcharacterize their microstructure, mechanical properties, GFA, and thermal properties. In the 2ndyear, themajor work will focus on the process study of MG powder manufacturing and thermoplastic forming. Themicrostructure change of hot-pressed Ti-based BMGF will be investigated and working window ofthermoplastic forming process will be established. For the 3rd year, based on the experimental results of 2ndyear study on the thermoplastic forming process. The BMGFs with different porosity ratio (30~60 vol.%) willbe produced by hot-pressing method. The surface morphology, mechanical properties, corrosion resistanceability will be evaluated. A selected BMGF with suitable pore size, mechanical properties, and Young’smodulus comparable to the human bone will be fabricated for the experiment of bone cell growth by in-vitrotest. Hopefully, the Ti-based BMGFs could be applied into the biomedical implant in the future.