Effect of Zinc Coating on Mechanical Behavior of Al 7075

Abstract

The addition of zinc to aluminum with magnesium or copper produces heat treatable alloys of highest strength which can be used for structural applications. This work is an attempt to investigate any improvement in hardness and fracture toughness by coating aluminum 7075 alloy with zinc. The zinc coated aluminum 7075 alloy was fabricated using Time Dependent Electro-Plating Technique. The thickness of the coating is a function of time. The varying thickness of zinc coating was obtained based on the time estimates, which includes 10, 15 and 20 microns. Specimens were prepared according to ASTM standards, which were then tested for mechanical properties such as surface hardness, tensile strength and fracture toughness at different loading conditions. The results, when compared to the uncoated aluminum alloy showed significant improvement in Hardness (87 RHN). The hardness increased slightly compared to that of uncoated surface and showed no increase with the increase in the thickness of coating. The yield stressof zinc coated aluminum alloy increased (587.11 N/mm2) when compared to uncoated aluminum alloy 7075 - T6 (537.12 N/mm2), with an increase in brittleness. The fracture toughness test on CT specimen under plain strain condition for coated specimen showed an increase in KIC value by 7.25 % compared to that of uncoated aluminum 7075–T6 alloy. Optical microscopy analysis shows that there is a good bonding of zinc coating on aluminum.