EFFECTS OF HfB2 ADDITION ON THE OXIDATION RESISTANCE, MICROSTRUCTURE, AND MECHANICAL PROPERTIES OF PRESSURELESS SINTERED ZrB2-SiC COMPOSITE

ABSTRACTThe effect of Si addition on microstructure and mechanical properties of dual two-phase intermetallic alloys was investigated. Si was added to the base alloy composition Ni75Al9V13Nb3 + 50 wt. ppm B by three substitution ways in which Si was substituted either for Ni, for Al and for V, respectively. The alloys added with 1 at.% Si showed a dual two-phase microstructure composed of Ni3Al (L12) and Ni3V (D022) phases, while the alloys added with over 2 at.% Si exhibited the same dual two-phase microstructure but contained third phases. The third phases were G phase (Ni16Si7Nb6) and A2 phase (the bcc solid solution consisting of Nb and V). Yield and tensile strength of the 1 at.% Si-added alloys were high in the alloy in which Si was substituted for Al but low in the alloys in which Si was substituted for Ni or for V, in comparison with those of the base alloy. Tensile elongation was lower than that of the base alloy irrespective of substitution ways. The density of the Si added alloys was close to or slightly lower than that of the base alloy. Oxidation resistance of the Si added alloy was increased. Si addition to the dual two-phase intermetallic alloys is beneficial for reducing the density and enhancing the oxidation resistance without a harmful reduction of strength properties.

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Phase Relations in the Si3N4-SiO2-MgO System and Their Interrelations with Strength and Oxidation Resistance. Dense Si3N4: Interrelation between Phase Equilibria, Microstructure and Mechanical Properties

10.21236/ada030408 ◽

1976 ◽

Author(s):

F. F. Lange

Keyword(s):

Mechanical Properties ◽

Phase Equilibria ◽

Oxidation Resistance ◽

Phase Relations ◽

Microstructure And Mechanical Properties

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Microstructure and mechanical properties of novel ternary electroconductive ceramics

Journal of Materials Research ◽

10.1557/jmr.2004.0428 ◽

2004 ◽

Vol 19 (11) ◽

pp. 3343-3352 ◽

Cited By ~ 7

Author(s):

Diletta Sciti ◽

Stefano Guicciardi

Keyword(s):

Mechanical Properties ◽

High Temperature ◽

Oxidation Resistance ◽

Hot Pressing ◽

Room Temperature ◽

Matrix Material ◽

Ceramic Composites ◽

Microstructure And Mechanical Properties ◽

Electrical Conductors ◽

Poor Oxidation Resistance

Electroconductive ceramic composites, constituted of an insulating matrix (a composite AlN-SiC) containing 30 vol% of an electroconductive phase (MoSi2, ZrB2, or ZrC), were densified through hot-pressing. Microstructure and mechanical properties were compared to those of the AlN-SiC matrix material. All the ternary composites are good electrical conductors, with resistivities in the range 0.3 × 10-3to 4 × 10-3Ω·cm. Room temperature properties are improved by the addition of the electroconductive particles. Strength and toughness measurements at high temperature show that MoSi2-containing composite is stable up to 1300 °C (strength 611 MPa, toughness 3.7 MPa·m1/2), whereas ZrB2-containing composite is stable up to 1000 °C. ZrC-containing composite is not suitable for high-temperature applications due to poor oxidation resistance.

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