Effect of Pore Size, Morphology and Orientation on the Bulk Stiffness of a Porous Ti35Nb4Sn Alloy
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JMEPEG https://doi.org/10.1007/s11665-018-3380-0
Effect of Pore Size, Morphology and Orientation on the Bulk Stiffness of a Porous Ti35Nb4Sn Alloy Carmen Torres-Sanchez
, John McLaughlin, and Ross Bonallo
(Submitted November 18, 2017; in revised form February 24, 2018) The metal foams of a titanium alloy were designed to study porosity as well as pore size and shape independently. These were manufactured using a powder metallurgy/space-holder technique that allowed a fine control of the pore size and morphology; and then characterized and tested against well-established models to predict a relationship between porosity, pore size and shape, and bulk stiffness. Among the typically used correlations, existing power-law models were found to be the best fit for the prediction of macropore morphology against compressive elastic moduli, outperforming other models such as exponential, polynomial or binomial. Other traditional models such as linear ones required of updated coefficients to become relevant to metal porous sintered macrostructures. The new coefficients reported in this study contribute toward a design tool that allows the tailoring of mechanical properties through porosity macrostructure. The results show that, for the same porosity range, pore shape and orientation have a significant effect on mechanical performance and that they can be predicted. Conversely, pore size has only a mild impact on bulk stiffness. Keywords
elastic modulus, hypothesis-driven manufacture, pore morphology, porosity, TiNbSn
1. Introduction Tailoring mechanical properties, and in particular stiffness, through the introduction of engineered porosity in a matrix presents opportunities for the creation of multiphase and multifunctional materials. Considering one of the phases as void, or air, the exploitation of their structural, thermal, acoustic, filtration or wicking properties finds applications in a myriad of fields. For example, the stiffness-to-weight ratio can be optimized to match the mechanical properties of bone and these cavities may be engineered to promote cell regeneration and vascularization. This twofold role, along with a biocompatible material, ensures the successful long-term implantation of load-bearing orthopedic implants. This optimization also applies to lightweight composite materials used by the transport industry pursuing a greener approach. Automotive components made out of porous beams which perform on a par with their solid structural counterparts but weigh less will reduce fuel consumption and thereby generate lower CO2/ NOx emissions. Therefore, a design and manufacturing strategy that allows engineering the macrostructure of the porous material and permits the tailoring of its mechanical properties to suit the application is a much sought-after tool. An extensive body of work that relates mechanical properties to volumetric porosity in a porous solid has been reported in the literature, and well-established models have been reported over the years. There exists a general agreement that bulk porosity (or por
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