On the aging of a hyper-eutectic Zn-Al alloy

Abstract

Zinc alloys are widely used in different fields, like handles and locking, fashion and design as well as automotive
or electronics, thanks to their good mechanical and technological properties combined with low cost and easy
formability. A limit to a wider use of these alloys is the aging phenomenon that causes a drop in their mechanical
properties in time. In order to improve their use in competition with more expensive copper and aluminum alloys,
in the last years the research has been addressed to develop new Zn-alloys compositions. One of these new
alloys, containing 15 wt% of Al and 1 wt% of Cu, appears to be suitable for both foundry and plastic deformation
forming processes, as resulted from preliminary laboratory and industrial trials. Being a newly developed alloy,
many properties have still to be investigated, to better understand the effective potentiality for proper industrial
applications. In this paper the ageing behavior of die-cast Zn-15Al-1Cu hyper-eutectic alloy was studied by means
of tensile tests and microstructural analyses. It was demonstrated that the alloy suffers from a drop in mechanical
properties, in particular at the very beginning of soaking at high temperature. A first analysis of the microstructure
by optical and scanning electron microscope was not able to fully point out the causes of the aging phenomenon.