Correlation between unsteady-state solidification thermal parameters and microstructural growth of Zn–8 mass% Al and Zn–8 mass% Al–XBi tribological alloys

Hypereutectic Zn–Al Alloys: Microstructural Development under Unsteady-State Solidification Conditions, Eutectic Coupled Zone and Hardness

“…The microstructural analysis performed at the longitudinal section of the DS casting (Figure 11b) revealed that the primary phase developed in the form of columnar dendrites. A previous study performed with the hypereutectic Zn-8wt.%Al and Zn-8wt.%Al-Xwt.%Bi (X = 1.5, 2.3, and 3.0) alloys, solidified under unsteady-state heat flow conditions, has shown that the primary phase developed in the form of predominantly equiaxed dendrites for both binary and ternary alloys [20]. The change in the dendrite structure may be related to the increase in the alloy Al content.…”

“…Such exponents values have been used to describe the growth of eutectic colonies for Al-6.3wt.%Ni [55] and Bi-2.5wt.%Ag alloys [56]. The experimental values of λ L of the hypereutectic Zn-8wt.%Al alloy that solidified under transient conditions were also shown to fit the classical eutectic growth law [20] with the expression λ L = 0.35V E −1/2 and λ L = 0.75 ṪE replacing it into the aforementioned Jackson-Hunt expression, the resulting expression for λ can be expressed as a function of Ṫ −1/4 . Such exponents values have been used to describe the growth of eutectic colonies for Al-6.3 wt.%Ni [55] and Bi-2.5 wt.%Ag alloys [56].…”

“…Such exponents values have been used to describe the growth of eutectic colonies for Al-6.3 wt.%Ni [55] and Bi-2.5 wt.%Ag alloys [56]. The experimental values of λL of the hypereutectic Zn-8 wt.%Al alloy that solidified under transient conditions were also shown to fit the classical eutectic growth law [20] with the expression λL = 0.35VE −1/2 and λL = 0.75 ṪE −1/4 . The increase in either cooling rate or growth rate induces a decrease in the microstructural spacing [57,58].…”

“…The secondary dendritic arm spacing (λ2) as a function of thermal parameters is displayed in Figure 17. The data are compared with an experimental growth law of the hypereutectic Zn-8wt.%Al alloy [20], also solidified under transient conditions. It can be ob- The increase in either cooling rate or growth rate induces a decrease in the microstructural spacing [57,58].…”

“…Therefore, it is expected that the Al content influences the solidification behavior and, consequently, the microstructure evolution [19]. Al-and Zn-rich solid solutions are, respectively, known as (Al) and (Zn) [20,21] or α and η [19,22], which are distributed in a specific manner depending on the Al content and the cooling process during and after solidification. Li et al [9] studied the effect of Al content on the microstructure of several Zn-Al alloys coatings and found that the Zn-0.6wt.%Al alloy consists of equiaxed η-Zn grains surrounded by narrow grain boundaries, while the Zn-1.5wt.%Al alloy is formed by η-Zn grains, Zn-Al dendritic eutectoid structure and lamellar Zn-Al eutectoid structure.…”