Evaluation of A(sub 5)Si(sub 3)Z(sub x) intermetallics for use as high temperature structural materials.

摘要

Refractory intermetallic silicides are receiving increasing consideration for use as high temperature structural materials. A(sub 5)Si(sub 3) compositions are particularly interesting due to their ability to incorporate a variety of interstitial ternary additions. These ternary additions present a unique opportunity to potentially tailor physical properties. Previous experimental work has shown that these additions can decrease the inherent thermal expansion anisotropy of Ti(sub 5)Si(sub 3). This paper reviews some of the literature with respect to binary and ternary silicides of the form A(sub 5)Si(sub 3)Z(sub x). Recent experimental work by the authors on two promising compositions, Ti(sub 5)Si(sub 3) and Mo(sub 5)Si(sub 3), is discussed. Interstitial additions substantially improve the isothermal oxidation resistance of both Ti(sub 5)Si(sub 3) and Mo(sub 5)Si(sub 3). The lattice parameter of Ti(sub 5)Si(sub 3) is significantly changed by ternary interstitial additions, indicating the extensive solubility of Ti(sub 5)Si(sub 3) for such additions. The level of similar additions affects the phase assemblage of Mo(sub 5)Si(sub 3). Hardness and toughness values from indentation measurements for selected compositions are given.