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.

PDF 2008.pdf Restricted to Registered users only Download (923kB) | Request a copy

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
Publication:	Intermetallics
Publisher:	Elsevier
Additional Information:	Copyright of this article belongs to Elsevier.
Keywords:	Molybdenum silicides;Brittleness and ductility;Fracture mode;Oxidation.
Department/Centre:	Division of Chemical Sciences > Materials Research Centre
Date Deposited:	17 Jul 2008
Last Modified:	19 Sep 2010 04:47
URI:	http://eprints.iisc.ac.in/id/eprint/15076

Actions (login required)

View Item