Processing high-temperature refractory-metal silicide in-situ composites

Abstract

Authors' Note: All compositions are given in atom percent. -temperature, refractory-metal, intermetallic, in-situ composites consist of highstrength, niobium-based silicides with a niobium-based metallic toughening phase. A variety of processing schemes have been used to generate these in-situ composites, including solidification and vapor phase processes. Secondary processing, such as forging and extrusion, has also been employed. These composites offer an excellent balance of high-and low-temperature mechanical properties with promising environmental resistance at temperatures above 1,100°C. High B.P. Bewlay is a metallurgist with

The Effect of Alloying on Nb–Silicide Phase Stability

“…The present paper describes the effect of alloying on the crystallography of Nb 5 Si 3 and Nb 3 Si type phases. Microstructural analyses, electron backscatter diffraction pattern (EBSD), and X-ray diffraction data will be discussed.Nb-silicide in-situ composites typically form a niobium solid solution and Nb-silicide phase on solidification [1,2]. The present paper will show that the crystallography of the Nb 5 Si 3 phase that forms from the melt upon solidification is a function of the Hf, Ti, and Al concentrations in the Nb-silicide.…”

“…Nb-silicide in-situ composites typically form a niobium solid solution and Nb-silicide phase on solidification [1,2]. The present paper will show that the crystallography of the Nb 5 Si 3 phase that forms from the melt upon solidification is a function of the Hf, Ti, and Al concentrations in the Nb-silicide.…”

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Composites based on niobium solid solutions and niobium silicides, such as Nb 5 Si 3 (tI32 crystal structure) and Nb 3 Si (tP32 crystal structure), are presently being developed for very hightemperature structural applications [1,2]. The use of alloying additions of elements such as Hf, Ti, Cr and Al to improve composite properties has also been explored.

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“…The present paper will show that the crystallography of the Nb 5 Si 3 phase that forms from the melt upon solidification is a function of the Hf, Ti, and Al concentrations in the Nb-silicide. The composites were prepared by arc melting and heat treatment, as described previously [1]. The cast composites were also hot isostatically pressed (HIP) and homogenized.…”

Effects of W on high-temperature antioxidative properties of Nb/Nb5Si3 composite

“…Excellent mechanical properties have been achieved during the development of Nb SS /Nb 5 Si 3 composites [2][3][4][5]; The best compositions have fracture toughness values exceeding 20MPa·m 1/2 [2,5]. However, their poor oxidation resistance at intermediate and high temperatures is a major obstacle to their use in high temperature applications.…”