Influence of heat treatment on the microstructure and wear behavior of end-chill cast Zn–27Al alloys with different copper content

Abstract

The aim of this paper was to study the effect of heat treatment on the microstructure and wear behavior of Zn-27Al alloys with different copper content. In order to study the relationship between microstructure features and wear behavior, the alloys prepared by an end-chill cast apparatus and then heat treated. Heat treatment procedure involved solutionizing at temperature of 350°C for 72 h followed by cooling within the furnace to room temperature. Microstructural characteristics of as-cast and heattreated alloys at different distances from the chill were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction. Wear tests were performed using a pin-on-disk test machine. To determine the wear mechanisms, the worn surfaces of the samples were also examined by SEM and EDS. Results showed that heat treatment led to the complete dissolution of as-cast dendritic microstructure and formation of a fine lamellar structure with well-distributed microconstituents. Moreover, addition of copper up to 1 wt% had no significant change in the microstructure, while addition of 2 and 4 wt% copper resulted in formation of e (CuZn 4 ) particle in the interdendritic regions. The influence of copper content on the wear behavior of the alloys was explained in terms of microstructural characteristics. Delamination was proposed as the dominant wear mechanism.

Investigation of microstructural change and damping behaviour of Zn–27Al–1Cu alloy in different aging periods

“…This structural change is evident from the difference between the microstructure of the alloy aged for 2.5 h and the alloy aged for 5 h given in Figure 4. The microstructure of the as-cast alloy formed as a result of solidification and the microstructural changes after heat treatment are compatible with previous studies on similar Zn-Al based alloys (Yang et al, 2013;Chen et al 2015;Jeshvaghani et al, 2016;Movahedi et al, 2019;Ferreira-Palma et al, 2021).…”

“…Moreover, heat treatment increased the dissolution of the ε phase in the matrix, resulting in a more homogeneous structure with dispersed precipitates. The microstructure formed after casting resulted from the solidification mechanism (Turhal & Savaşkan, 2003;Jeshvaghani et al, 2016). However, the microstructural changes of the alloy after heat treatment resulted from the solution treatment and aging-activated precipitation mechanisms.…”

“…It found that the addition of copper in the range of 1-3 wt. % improves the strength and hardness of the Zn-Al alloys while reducing the ductility, due to solid solution hardening and the formation of relatively hard intermetallic ε (CuZn4) and T′ (Al4Zn3Cu) phases (Jeshvaghani et al, 2016). Some researchers have designed a series of typical alloys such as Zn-15Al-1Cu (Rollez et al, 2017), Zn-21Al-2Cu (Hernández-Rivera et al, 2017, Zn−25Al-3Cu (Savaşkan & Tan, 2015), Zn-26Al-1.5Cu-0.9Ni (Choudhury et al, 2002), Zn-27Al-3Si (Mao et al, 2015), Zn-38Al-2.5Cu-0.55Si (Ting et al, 2016) and Zn-40Al-2Cu-2Si (Savaşkan et al 2021), apart from the commercial ZA alloys.…”