Investigation of the effect of cr additives on mechanical properties and microstructure of the zinc-aluminum-based Za-12 alloy

At present, ZA alloys are used in many areas/applications instead of conventional casting alloys such as Al alloys, brass, bronze and cast iron alloys. This is reason that ZA alloys have good castability, high strength; good wear resistance and high ratio of strength to weight. The most important advantage of ZA alloys, in addition to its superior mechanical properties, is to be cast by all of common casting methods.In this study, the effect of the chromium on microstructure and the mechanical properties (tensile strength, hardness, impact strenght and fatigue strenght ) of the squeeze cast zinc-aluminium based ZA?12 alloy have been investigated in the range from 0.01 % to 0.1 % Cr.The results showed that while the addition of the chromium increases the hardness of the ZA?12 alloy, considerably decreases the impact strength. The impact strenght only increased for the ZA?12 alloy containing 0.01 wt.%Cr, then decreased with further increase in Cr content. The ultimate tensile strength (UTS) and fatigue strenght of the standard alloy have been increased with Cr addition up to 0.03 % and then decreased with further increase in chromium content. Metallographic examinations revealed that chromium formes complex shaped particles in the microstructure. It can be suggested that these particles cause a decrease in UTS and fatigue resistance of the ZA?12 alloy.Keywords: Squeeze Casting, Zn-Al Alloys, ZA?12, Hardness, Tensile Strenght, Mechanical Properties.