Mechanical Behavior of Porous Magnesium Manufactured by Powder Metallurgy

Ning Zou

Porous Magnesium (Mg) is promising for biomedical, structure, and energy material. The introduction of porous structure into Mg improves biocompatible stability, decreases weight, increases mechanical damping ability, and has superior surface area. However, mechanical properties of porous Mg are deteriorated, compared with dense Mg. To overcome the limitation, we aim to enhance mechanical properties of porous Mg by three specific tasks: applying novel space holders (camphene and polystyrene (PS)), adding magnesium oxide (MgO) nanoparticles, and designing multi-layered structure. Microstructure and mechanical behavior of porous Mg manufactured by powder metallurgy using camphene as the novel space holder were researched. The manufactured porous Mg achieved higher purity, smaller average pore size, and higher ultimate compressive strength (UCS), compared with porous Mg fabricated by powder metallurgy using particulate space holders. Strength predictions by Gibson-Ashby model matched with experimental data. Porous Mg manufactured by powder metallurgy using PS as another novel space holder was investigated. Using lower molecular weight PS as the space holder introduced less amount of MgO into porous Mg. Hot processing PS contributed to fabricating porous Mg with higher hardness. MgO is a common impurity in porous Mg manufactured by powder metallurgy. A quantitative analysis on how the amount of MgO nanoparticles affected mechanical behavior of porous Mg processed by powder metallurgy was investigated in experimental and theoretical aspects. Strength of porous Mg-MgO composites showed the fluctuation tendency with the increase of MgO wt.%. Different theories for yield strength and Young’s modulus were used and compared with the experimental results. Different layer numbers of multi-layered porous Mg, a type of functionally graded material containing layers of 4.1% porous Mg and 21.8% porous Mg, were manufactured by powder metallurgy. Mechanical behavior of multi-layered porous Mg and uniform porous Mg samples were investigated and compared. Deformation of multi-layered porous Mg started first at 21.8% porous Mg with low strength and progressed towards 4.1% porous Mg with high strength. Experimental strain-stress curves of multi-layered porous Mg can be well predicted and explained by utilizing different theoretical methods: mechanics of materials prediction, Hangai’s prediction, modified mechanics of materials prediction, and phenomenological model prediction.

Mechanical Behavior of Porous Magnesium Manufactured by Powder Metallurgy

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