Microstructure and Wear Performance of ECAP Processed Cast Al–Zn–Mg Alloys

Abstract

In the present investigation, wear performance of equal channel angular pressing (ECAP) processed cast Al–Zn–Mg alloys under dry sliding wear conditions was studied against a steel disc. Initially, Al–Zn–Mg alloys (with 5, 10, 15% zinc and 2% magnesium) were ECAP processed. After ECAP, grain size was reduced and enhancement in the hardness was observed. Wear resistance of the alloys increased after ECAP processing. Wear resistance of the alloys also increased when the quantity of the zinc was increased in the alloys. But, wear resistance of all three alloys decreased with increase in the load and the sliding speed. Coefficient of friction of the alloys decreased after ECAP processing. Coefficient of friction of the alloys also decreased when the quantity of the zinc was increased in the alloys. Coefficient of friction of all three alloys increased with increase in the load and the sliding speed. Irrespective of the alloy composition and applied load, worn surfaces of the cast and homogenized samples were composed of plastic deformation, scratches and micro-ploughing. On the other hand, in ECAP processed samples, morphology of the worn surfaces depended on the applied load. Abrasive wear is the main wear mechanism perceived in cast and homogenized samples at all loads. While in ECAP processed samples, the wear mechanism shifted from adhesive and oxidation wear to abrasive wear with increase in the load. Formation of oxide layers on the surface of the sample increased with increase in the ECAP passes. In ECAP processed samples, transfer of iron content from the disc to the sample surface was identified.