Effects of combined use of inoculation and modification heat treatment on microstructure, damping and mechanical properties of Zn–Al eutectoid alloy

Abstract

Inoculation and modification heat treatments were conducted on the Zn–Al eutectoid alloy (ZA22) with the aim of grain refinement. Evolution law of microstructure, and changes of damping and mechanical properties of resultant specimens were also studied. It was found that inoculation could refine the primary α phase and effectively improved the damping arising from the reverse eutectoid transformation, as well as the tensile strength and elongation. After modification heat treatments, all original phases and structures disappeared completely. The newly formed ZA22 alloy only consisted of sub-micron granular eutectoid structure. The significantly increased density of interfaces and the change in α/η interface microstructure resulted in remarkable improvement of damping over the whole temperature range. The damping of all ZA22 alloys showed obvious strain amplitude dependence in two strain regions, which has been ascribed to the depinning of sliding interfaces and the dynamic recrystallization due to microplasticity at the surface of the specimens, respectively. Sub-micron grains and uniform composition of granular eutectoid structure could effectively promote the sliding of grain boundaries, which leaded to the appearance of room temperature superplasticity.