Tailoring microstructure, tensile properties and fracture process via transient directional solidification of Zn-Sn alloys

The aim of the present study is to determine interrelations of microstructure length-scale, tensile properties and fracture mechanisms of hypoeutectic Zn-Sn alloys. Three compositions were subjected to transient directional solidification: Zn-10, 20 and 40 wt%Sn. Grainy-faceted cleavage has been observed as the predominant mode of fracture, which propagated across the Zn-rich plate cells. A clear influence of the formed microstructure and proportion of eutectic may be noted in the fracture features, with alveolar structures also appearing in fracture surfaces. Growth laws relating the eutectic spacing with the growth rate are proposed, which are able to encompass both steady-state and transient solidification conditions. Hall-Petch type equations are developed relating the yield and ultimate tensile strengths, σy and σu, respectively, to the cellular spacing, λ, in which smaller λ values resulted in higher σy and σu.