Dendritic Spacing/Columnar Grain Diameter of Al–2Mg–Zn Alloys Affecting Hardness, Tensile Properties, and Dry Sliding Wear in the As‐Cast/Heat‐Treated Conditions

Abstract

Inter‐relations of solidification conditions, as‐cast and heat‐treated structures, and mechanical properties are extremely useful in the design of components, especially Al‐based alloys. Herein, the effects of secondary dendrite arm spacing (λ2) and columnar grain diameter (CGD) on hardness, tensile, and dry sliding wear responses of Al−2Mg‐(5 and 8)Zn (wt%) alloys in the as‐cast and heat‐treated conditions, respectively, are focused upon. The alloys are melted and solidified in an instrumented upward directional solidification apparatus under nonsteady‐state heat transfer conditions. Samples are cut from the solidified ingots and subjected to the T6 heat treatment. Samples are characterized metallographically by optical and scanning electron microscopies and mechanically by Brinell hardness, tensile, and dry sliding wear tests. It is found that higher Zn concentration and solidification cooling rates refine λ2 and the CGD. Hardness and tensile properties are improved with the decrease in λ2 in the as‐cast condition of both alloys. After heat treatment, all these properties increase with the decrease in CGD. Wear parameters show that only the alloy having a higher Zn content is associated with better wear resistance. Correlations between the wear rate as a function of λ2 and CGD are established by experimental equations.