Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
The influence of microstructure of the fiber-matrix interface on the interfacial shear strength, measured using a fiber-pushout technique, has been examined in a sapphire-fiber-reinforced NiAl(Yb) matrix composite under the following conditions: (1) as-fabricated powder metallurgy (PM) composites, (2) PM composites after solid-state heat treatment (HT), and (3) PM composites after directional solidification (DS). The fiber-pushout stress-displacement behavior consisted of an initial ''pseudoelastic'' region, wherein the stress increased linearly with displacement, followed by an ''inelastic'' region, where the slope of the stress-displacement plot decreased until a maximum stress was reached, and the subsequent gradual stress decreased to a ''frictional'' stress. Energy-dispersive spectroscopy (EDS) and X-ray analyses showed that the interfacial region in the PM NiAl(Yb) composites was comprised of Yb2O3, O-rich NiAl and some spinel oxide (Yb3Al5O12), whereas the interfacial region in the HT and DS composites was comprised mainly of Yb3Al5O12. A reaction mechanism has been proposed to explain the presence of interfacial species observed in the sapphire-NiAl(Yb) composite. The extent of inter facial chemical reactions and severity of fiber surface degradation increased progressively in this order: PM < HT < DS. Chemical interactions between the fiber and the NiAl(Yb) matrix resulted in chemical bonding and higher interfacial shear strength compared to sapphire-NiAl composites without Yb. Unlike the sapphire-NiAl system, the frictional shear stress in the sapphire-NiAl(Yb) composites was strongly dependent on the processing conditions.
Tewari, Surendra N.; Asthana, R.; Tiwari, R.; Bowman, R. R.; and Smith, J., "Influence of Interfacial Reactions on the Fiber-Matrix Interfacial Shear-Strength in Sapphire Fiber-Reinforced Nial(Yb) Composites" (1995). Chemical & Biomedical Engineering Faculty Publications. 24.
Tewari, S.N., Asthana, R., Tiwari, R., Bowman, R.R., & Smith, J. (1995). Influence of Interfacial Reactions on the Fiber-Matrix Interfacial Shear-Strength in Sapphire Fiber-Reinforced Nial(Yb) Composites. Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science 26, 477-491.
Copyright 1995 ASM International. This paper was published in Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science, Vol. 26, Issue 2, pp. 477-491 and is made available as an electronic reprint with the permission of ASM International. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplications of any material in this paper for a fee or for commercial purposes, or modification of the content of this paper are prohibited.
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