Showing papers by "Francis Delannay published in 1993"

Processing of functional-gradient WC-Co cermets by powder metallurgy

Abstract: WC-Co cemented carbides are widely used as machining tools, mining tools, and wear-resistant parts. Multilayer graded structures with Co content ranging from 10 to 30 wt.% from one side of the structure to the other have been prepared by using either solid-state or liquid-phase sintering. Post-hot isostatic pressing was used to improve the final density of some of these samples. Special attention was given to the homogenization process that occurs during liquid-phase sintering of the graded structures.

Stainless steel fibre reinforced aluminium matrix composites processed by squeeze casting : relationship between processing conditions and interfacial microstructure

Abstract: This work investigates the influence of some processing parameters on the extent of interfacial reaction in squeeze cast aluminium matrix composites reinforced with 12 mu m diameter, continuous stainless steel fibres. The average thickness of the reaction layer at fibre/matrix interfaces was measured by image analysis. When casting was made in a die at room temperature, the thickness of the reaction layer was affected on a distance of several mm from the lateral surface or from the bottom of the preform. The results indicate that the major part of the reaction occurs before solidification of the liquid metal. The control of the extent of interfacial reaction can be achieved through optimization of both infiltration parameters and features of the preform such as the volume fraction of the fibres.

Processing and properties of metal matrix composites reinforced with continuous fibres for the control of thermal expansion, creep resistance and fracture toughness

Abstract: Al-, Zn-, and Cu-based matrix composites reinforced with continuous fibres of carbon, SiC, Al2O3, or steel have been processed by squeeze casting or powder metallurgy. Interface reactions can be controlled by alloying additions in the matrix. Interface adhesion has been characterized from the distributions of fibre pull-out lengths on fracture surfaces. Thermal expansion curves reveal the magnitude of the stress transfer at interfaces. In the case of low melting point matrices, ductile steel fibres offer the best combination of fracture toughness and creep resistance.

Effect of V and Re additions on the creep properties of γ/γ-α eutectic composites

Abstract: Alloying a ternary monovariant Ni-Al-Mo eutectic alloy with vanadium and rhenium has been investigated as a means to increase the creep strength at elevated temperature. The creep properties of directionally solidified eutectic γ/γ'-α alloys with nominal composition Ni-31Mo-6Al, Ni-32Mo-6Al-1.4V and Ni-30Mo-6Al-1.6V-1.2Re (wt.%) have been determined using strain rate change test. The tests were conducted under vacuum at temperatures between 1223 and 1323 K. Comparison of the stress-strain rate behaviour to that for directionally solidified Ni-Al-Mo eutectic alloy has revealed that the additions of vanadium and rhenium increase the steady-state stress at given creep rate and temperature by 11 to 20%. This improvement is higher at higher temperatures and lower creep rates. The steady-state stress has been found to depend strongly on creep rate and temperature. The measured power law exponents varied between 6.7 and 7.9 over the studied temperature range. The activation energies for creep were calculated to range between 471 and 517 kJmol -1 . The ductility of these eutectic composites was high, typically ranging from 40 to 60% reduction of area and from 15 to 38% elongation

Effect of V-addition and Re-addition On the Creep-properties of Gamma/gamma'-alpha Eutectic Composites

Abstract: Alloying a ternary monovariant Ni-Al-Mo eutectic alloy with vanadium and rhenium has been investigated as a means to increase the creep strength at elevated temperature. The creep properties of directionally solidified eutectic gamma/gamma'-alpha alloys with nominal composition Ni-31Mo-6A1, Ni-32Mo-6Al-1.4V and Ni-30Mo-6A1-1.6V-1.2Re (wt.%) have been determined using strain rate change test. The tests were conducted under vacuum at temperatures between 1223 and 1323 K. Comparison of the stress-strain rate behaviour to that for directionally solidified Ni-Al-Mo eutectic alloy has revealed that the additions of vanadium and rhenium increase the steady-state stress at given creep rate and temperature by 11 to 20%. This improvement is higher at higher temperatures and lower creep rates. The steady-state stress has been found to depend strongly on creep rate and temperature. The measured power law exponents varied between 6.7 and 7.9 over the studied temperature range. The activation energies for creep were calculated to range between 471 and 517 kJmol(-1). The ductility of these eutectic composites was high, typically ranging from 40 to 60% reduction of area and from 15 to 38% elongation..