EFFECT OF HEAT-TREATMENT ON THE INSOLUBLE INTERMETALLIC PHASES PRESENT IN AN AA-6063 ALLOY

The microstructure of a semi-continuously cast AA 6063 alloy was inves tigated and the transformation of insoluble intermetallic phases by ap plied heat treatment was studied by selective dissolution of the matri x. Residual intermetallics were characterized using energy-dispersive X-ray analysis, X-ray and electron diffraction techniques. Transformat ion of beta-AlFeSi phase, which is known to have detrimental effects o n the surface finish of the extrudates, to more favourable alpha-AlFeS i phase by heat treatment was determined.