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

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.

Stainless-steel Fiber-reinforced Aluminum-matrix Composites Processed By Squeeze Casting - Relationship Between Processing Conditions and Interfacial Microstructure

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 Fibers for the Control of Thermal-expansion, Creep Resistance and Fracture-toughness

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