Mechanical properties as a function of thermal parameters and microstructure of Zn–Al castings

The imposition of a wide range of operational conditions in foundry and casting process generates, as a direct consequence, a diversity of solidification structures. Structural parameters such as grain size and interdendritic spacings are highly influenced by thermal behavior of the metal/mould system during solidification, consequently imposing a close correlation between the described system and the resulting microstructure. The mechanical properties of an alloy depend on the solidification microstructural arrangement. Under this circumstance, grain size, interdendritic spacings, casual porosities, segregated products and other phases will define the mechanical behavior of the alloy, represented by stresses and/or strains. Expressions correlating the mechanical behavior with microstructure parameters are very useful for a previous planning of the solidification conditions in terms of a determined level of mechanical resistance which is intended to be attained, i.e. to settle a way of programming the microstructure and the mechanical properties as well. Particularly, the literature in this field presents relationships between the material yield strength and the grain size, such as the Hall–Petch’s equation. The aim of the present work is to investigate the influence of heat transfer on solidification microstructure of Zn–Al alloys and the correlation with mechanical properties. Experimental results include transient metal/mould heat transfer coefficients, secondary dendrite arm spacings and ultimate and yield strengths as a function of solidification conditions imposed by the metal/mould system.