Fibre-reinforced metal-matrix composites

Extrusion is shown to be a thermally activated process in which mass transfer is important. Speed effects may be recognized in the mean equivalent strain rate and then combined with temperature eff...

Temperature and speed effects in hot extrusion of aluminium alloys

Development of recovered dislocation substructures during plastic flow

A study of the extrusion of sintered porous metal

Most aluminium alloys are produced in complex shapes and hence it is important to investigate the effect of geometry on extrudability. Results of extrusion experiments which show that shape geometry appears to alter the relationship between the temperature-compensated strain rate and the hyperbolic sine stress function are presented. It is suggested that this anomaly is the result of inconsistencies in calculation of strain rate and temperature and a correction factor is proposed to relate extrusion experiments to a simple torsion test. It is shown that this correction factor can be related to the logarithm of a modified extrusion ratio. It is concluded that extruded structure, and hence some properties, may be predicted for shaped as well as rod extrudates.

Effect of section geometry on extrudability of Al–Cu–Mn alloy

The mechanical properties of aluminium alloy powder compacts vary throughout the quasi-static deformation zone. Experimental evidence has suggested that the flow stress is dependent upon both strain and strain rate such that an equation of the form δ = Aeme n best describes material behaviour under deformation conditions. This paper presents a mathematical analysis of the deformation by modifying an axi-symmetric upper-bound solution and utilizing a penalty function approach to minimization to obtain the stress constants. It is shown that for a cast billet this approach predicts the specific pressure accurately and that for powder compacts the constants k, m, and n may be obtained and a satisfactory prediction of pressure facilitated.

M. G. Tutcher

Papers

Analysis of Specific Pressure Necessary to Extrude Aluminium Alloy Compacts