Modulus

Abstract: The fracture toughness, hardness, and Young's modulus of tantalum thin films are investigated based on nanoindentation measurements. A lower estimate of the fracture toughness of a 100 nm tantalum film is 0.28 +/- 0.07 MPa m(1/2). The hardness increases when reducing the film thickness whereas Young's modulus decreases slightly. More precisely, the hardness of the 100 nm thick film is four times higher than the bulk behavior. A simple theoretical model, based on the connection between Young's modulus and melting temperature, predicts an inverse grain size variation in Young's modulus confirmed by experiments. (C) 2010 American Institute of Physics. [doi:10.1063/1.3496000]

Abstract: Body-centered cubic (BCC) multi-principal element alloys (MPEAs) have drawn particular attention as orthopedic implant materials recently, due to their high strength and excellent biocompatibility. However, these alloys often exhibit limited tensile ductility and relatively high Young's modulus, which remain challenges for their potential biomedical applications. In this work, a synergistic design of high-performance biomedical MPEAs based on the principles of valence electron concentration theory and average shear modulus mismatch for solid-solution strengthening is reported. Three TiZrNbTa MPEAs (Ti45Zr45Nb5Ta5, Ti42.5Zr42.5Nb5Ta10, Ti40Zr40Nb5Ta15) with different Ta content were designed. All the alloys exhibited single BCC structure and possessed outstanding tensile ductility (≥18.8%), as well as low Young's modulus (59.3±2.1–73.1±1.0 GPa). The yield strengths of these alloys are increasing with the increase of the Ta content, which can be correlated with the average shear modulus mismatch. In particular, Ti40Zr40Nb5Ta15 alloy exhibits the highest yield strength (∼990.0±14.3 MPa) and high wear resistance for biomedical applications. Theoretical calculation suggested that the strength of the TiZrNbTa alloys is mainly attributed to the solid-solution strengthening effect, and increasing the Ta content can effectively enhance this effect.