Machinability performance evaluation in turning of Zn-40Al-2Cu-2Si alloy: The effect of solutionizing-artificial aging

In this study, structural, mechanical, and machinability properties of the Zn-40Al-2Cu-2Si material obtained by gravity die casting were revealed in the casted and heat treated (HTed) states. Heat treatment (HT) was performed using 24 h at 375 ˚C for solutionizing, quenching, and 2 h at 150 ˚C for aging. The microstructure of the casted material was determined to comprise α-Al, η, α+ η, ε (CuZn 4 ) phases and Si particles. After HT, it was observed that the phases precipitated in the inner part of the grains forming the α-Al phase and in the boundary regions. However, no dimensional and relative difference was observed in the Si particles. It was stated that the hardness and tensile strength of the material increased while elongation to fracture decreased with the HT. Machinability tests were performed with PVD-ZrN+TiAlN coated carbide using various cutting speeds ( Vs ), feed rates ( f ), and a fixed depth of cut (DoC) in turning. It was revealed that the solutionizing-aging process developed the machining characteristics of the material. While V was inversely proportional to cutting force ( F ), surface roughness ( Ra ), and built-up edge (BUE) at constant f , these variables changed directly proportional to the f at constant V . The lowest F , Ra, and built up edge (BUE) were observed at V of 250 m/min and f of 0.04 mm/rev. The highest of these results were observed at V of 150 m/min and f of 0.12 mm/rev. Feed marks, smeared layers, and cavities were seen on the cut surfaces. It was observed that the chip creation turned into a shorter and more brittle structure compared to the as-cast alloy due to solutionizing-aging during machining.