Influence of heat treatment parameters on the microstructure and properties of some zinc-based alloys

• Published in: Journal of materials science 1996-12, Vol.31 (23), p.6317-6324
• Main Authors: PRASAD, B. K, PATWARDHAN, A. K, YEGNESWARAN, A. H
• Format: Article
• Language: English
• Subjects: Applied sciences; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Metals. Metallurgy; Other heat and thermomechanical treatments; Physics; Treatment of materials and its effects on microstructure and properties
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/bf00354455

The present investigation deals with microstructure and property related changes in a zinc-based alloy induced by varying solutionizing and aging durations and (solutionizing) temperatures. The influence of partially replacing copper by nickel and silicon in the alloy composition has also been studied on similar lines. The microstructure of the as cast, nickel /silicon-free alloy revealed primary alpha dendrites surrounded by eutectoid and eutectic alpha + eta in the interdendritic regions along with the metastable epsilon phase. The addition of Ni and Si partially altered the basic microstructure of the alloy by forming primary Si particles and intermetallic compounds. Solutionizing led to the breaking of the dendritic structure and redistribution of the alloying elements while aging formed the T' phase. The morphology of Si particles and the (Ni containing) intermetallic compound was noted to be unaltered in the Ni and Si containing alloy during the heat treatment. The hardness of the alloys increased during solutionizing while it reduced after aging when compared with that of the as cast sample value. The presence of Si and Ni led to an increase in the hardness of the alloy. It also enabled the alloy to retain a higher hardness during the heat treatment. An increased solutionizing duration led to an initial increase in the hardness with a peak value being obtained which was followed by a reduction in the hardness. The presence of Ni and Si in the alloy reduced the tendency of a reduction in hardness beyond the peak hardness. The microconstituents also lowered the detrimental influence of the coarsening of the T' phase. The density of the Ni/Si-free alloy varied in a narrow range. However within this range, solutionizing caused an increase in the density with duration followed by a reduction and finally a steady state value. The presence of Si and Ni increased the resistivity of the alloy.