Metal-matrix composite materials composed of an austenitic stainless steel with different ceramic particle reinforcements were investigated in this study. The test specimens were prepared via a powder metallurgical processing route with extrusion at room temperature. As reinforcement phase, either magnesia partially stabilized zirconia or aluminium titanate with a volume content of 5% or 10% was used. The mechanical properties were determined by quasi-static compressive and tensile loading tests at ambient temperature. The microstructure characteristics and failure mechanisms during deformation contributing to significant changes in strength and ductility were characterized by scanning electron microscopy including energy dispersive X-ray spectroscopy and electron back-scatter diffraction, and by X-ray diffraction. The composite materials showed higher stress over a wide range of strain. Essentially, the deformation-induced formation of α′-martensite in the steel matrices is responsible for the pronounced strain hardening. At higher degrees of deformation, the material behavior of the composites was controlled by arising damage evolution initiated by particle/matrix interface debonding and particle fracture. The particle reinforcement effects of zirconia and aluminium titanate were mainly controlled by their influences on martensitic phase transformations and the metal/ceramic interfacial reactions, respectively. Thereby, the intergranular bonding strength and the toughness of the steel/ceramic interfaces were apparently higher in composite variants with aluminium titanate than in composites with magnesia partially stabilized zirconia particles.
Metal-matrix composites composed of an austenitic stainless steel and magnesia partially stabilized zirconia were prepared via a powder metallurgical processing route with the ceramics-derived extrusion at room temperature. Various combinations of the base materials with zirconia volume fractions of 0, 5, and 10% were joined by applying an aqueous paste which forms the joint during thermal processing. The materials were tested under tensile loading at room temperature. The addition of zirconia particles led to a considerable decrease of the plasticity and ultimate tensile strength of the basic compositions. However, the strength of joint specimens was not limited by the bonding strength of the joining zone. Among all material combinations tested, failure occurred in the joining partner with the higher zirconia volume fraction and not at the joint interface. Thus, the strength of sinter-joined materials based on MMC with 0-10 vol% was limited by the strength of the base materials. The advance of the present sinter-joining method is the single thermal operation of the composite materials. The formation of a homogeneous bonding zone and the absence of a heataffected zone lead to negligible interference with the microstructure and the mechanical properties of the base materials.
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