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Full-Text Articles in Engineering
Influence Of Cr And W Alloying On The Fiber-Matrix Interfacial Shear-Strength In Cast And Directionally Solidified Sapphire Nial Composites, R. Asthana, R. Tiwari, Surendra N. Tewari
Influence Of Cr And W Alloying On The Fiber-Matrix Interfacial Shear-Strength In Cast And Directionally Solidified Sapphire Nial Composites, R. Asthana, R. Tiwari, Surendra N. Tewari
Chemical & Biomedical Engineering Faculty Publications
Sapphire-reinforced NiAl matrix composites with chromium or tungsten as alloying additions were synthesized using casting and zone directional solidification (DS) techniques and characterized by a fiber pushout test as well as by microhardness measurements. The sapphire-NiAl(Cr) specimens exhibited an interlayer of Cr rich eutectic at the fiber-matrix interface and a higher interfacial shear strength compared to unalloyed sapphire-NiAl specimens processed under identical conditions. In contrast, the sapphire-NiAl(W) specimens did not show interfacial excess of tungsten rich phases, although the interfacial shear strength was high and comparable to that of sapphire-NiAl(Cr). The postdebond sliding stress was higher in sapphire-NiAl(Cr) than in …
Development Of Nial-Based Intermetallic Alloys: Effect Of Chromium Addition, R. Tiwari, Surendra N. Tewari, R. Asthana, A. Garg
Development Of Nial-Based Intermetallic Alloys: Effect Of Chromium Addition, R. Tiwari, Surendra N. Tewari, R. Asthana, A. Garg
Chemical & Biomedical Engineering Faculty Publications
The mechanical behavior of dual-phase NiAl(Cr) microstructures, consisting of elongated primary NiAl grains aligned with an intergranular NiAl-Cr eutectic phase, produced by extrusion of a cast NiAl(Cr) alloy, has been examined. Chromium addition to create a dual phase NiAl-based aligned microstructure leads to large increases in the yield strength but no significant toughness improvement. This is achieved primarily by solid solution hardening and precipitation hardening. The constitutional hardening rate resulting from deviations from stoichiometry in the nickel-rich NiAl was estimated to be about 66 MPa per atomic per cent of nickel.
Influence Of Interfacial Reactions On The Fiber-Matrix Interfacial Shear-Strength In Sapphire Fiber-Reinforced Nial(Yb) Composites, Surendra N. Tewari, R. Asthana, R. Tiwari, R. R. Bowman, J. Smith
Influence Of Interfacial Reactions On The Fiber-Matrix Interfacial Shear-Strength In Sapphire Fiber-Reinforced Nial(Yb) Composites, Surendra N. Tewari, R. Asthana, R. Tiwari, R. R. Bowman, J. Smith
Chemical & Biomedical Engineering Faculty Publications
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 …
Influence Of Fabrication Technique On The Fiber Pushout Behavior In A Sapphire-Reinforced Nial Matrix Composite, R. Asthana, R. R. Bowman, Surendra N. Tewari
Influence Of Fabrication Technique On The Fiber Pushout Behavior In A Sapphire-Reinforced Nial Matrix Composite, R. Asthana, R. R. Bowman, Surendra N. Tewari
Chemical & Biomedical Engineering Faculty Publications
Directional solidification (DS) of ''powder-cloth'' (PC) processed sapphire-NiAl composites was carried out to examine the influence of fabrication technique on the fiber-matrix interfacial shear strength, measured using a fiber-pushout technique. The DS process replaced the fine, equiaxed NiAl grain structure of the PC composites with an oriented grain structure comprised of large columnar NiAl grains aligned parallel to the fiber axis, with fibers either completely engulfed within the NiAl grains or anchored at one to three grain boundaries. The load-displacement behavior during the pushout test exhibited an initial ''pseudoelastic'' response, followed by an ''inelastic'' response, and finally a ''frictional'' sliding …