Constitutive equations for use in prediction of flow stress during extrusion of aluminium alloys

AbstractConstitutive equations are reviewed and discussed in the context of extrusion. It is concluded that mainly because extrusion converts directly from cast to finished product a steady state equation is adequate for use in extrusion problems and that the Zener-Hollomon type of formulation is both convenient and defined for a number of aluminium alloys. Experimental work is presented to show that if the data are correctly interpreted by suitably allowing for temperature rise, then testing in either torsion or compression yields identical equations. The physical interpretation of the various constants is discussed. Evidence is presented that differing homogenisation treatments produce differing equations and the effects of heating and cooling rates are considered. The implications are discussed in some detail. Constitutive equations are quantified for 26 aluminium alloys.