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Production and Properties of 316L Stainless Steel Cellular Materials and Syntactic Foams

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Abstract

316L steel syntactic foams incorporating different mass percentages of soda lime borosilicate glass microspheres (3M™) as porosity-introducing particles are produced via metal powder injection moulding. Sintering is performed at 1200°C under controlled atmosphere for 1.5, 3, and 6 h. Microstructural features are examined using optical and scanning electron microscopy (SEM) as well as focused ion beam (FIB) preparation and EDX analysis. Response to quasi-static compressive and tensile loads is studied and interpreted based on structural characterization results. Melting of microspheres is observed, but cavities originally occupied by microspheres are maintained, while glass inclusions form in the surrounding matrix. A qualitative explanation of the underlying process is given. Evaluation of the stress–strain curve reveals a comparatively weak expression of the stress plateau matching the relatively low porosity. Analysis of tensile fracture surfaces indicates a shift of failure initiation sites from spinel type MnCr2O4 phases in the reference material to glass inclusions in foam samples. No major influence of sintering time on structural or mechanical characteristics is identified. Despite the adverse effects of microsphere melting, mechanical performance of 316L syntactic foams matches similar materials having Fe and Fe-based alloy matrices.

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