# Improved ductility and oxidation resistance in Nb and Al co-substituted $MoSi_2$

Dasgupta, T and Umarji, AM (2008) Improved ductility and oxidation resistance in Nb and Al co-substituted $MoSi_2$. In: Intermetallics, 16 (6). pp. 739-744.

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## Abstract

Polycrystalline samples of $(Mo_{1-x}Nb_x)(Si_{1-y}Al_y)_2$ with x = 0.0-0.03 and y = 0.0, 0.04 were prepared by arc melting followed by densification by hot pressing. The mechanical and oxidation behaviors of high density polycrystalline pellets were evaluated. Thermogravimetric analysis shows lower oxidation in $(Mo_{1-x}Nb_x)(Si_{0.96}Al_{0.04})_2$ samples compared to pure $MoSi_2$. X-ray diffraction analysis of the oxide scale revealed the presence of $\alpha-Al_2O_3$ peaks. Mechanical characterizations carried out on $(Mo_{0.99}Nb_{0.01})(Si_{0.96}Al__{0.04})_2$ composition show a marked improvement compared to that of unsubstituted $MoSi_2$. Micro-hardness measurements reveal a lowering of the room temperature hardness and stiffness compared to pure $MoSi_2$. Plastic deformation under compression is observed at room temperature with a yield stress of 500 MPa. The $K_{1c}$ value increased from $3.33 (\pm3) MPa m^{0.5}$ to $4.05 (\pm0.3) MPa m^{0.5}$ with the fracture mode being predominantly transgranular.

Item Type: Journal Article Copyright of this article belongs to Elsevier. Molybdenum silicides;Brittleness and ductility;Fracture mode;Oxidation. Division of Chemical Sciences > Materials Research Centre 17 Jul 2008 19 Sep 2010 04:47 http://eprints.iisc.ernet.in/id/eprint/15076