Effects of thermal conditions on the mechanical properties of squeeze cast ZA-27 alloy

Abstract

Squeeze casting is a generic term to specify a fabrication when solidification is promoted under high-pressure within a re-usable die. It is a metal-forming process, which combines permanent mould casting with die forging into a single operation where molten metal is solidified under applied hydrostatic pressure. Squeeze casting has a greater potential to produce less defective cast components contrary to the other conventional casting techniques. In the present study, the aim was to search thermal solidification behavior and mechanical properties of a squeeze cast ZA-27 alloy in three different pressure ranges. For this purpose, totally 20 samples were cast under 0,1 MPa, 100 MPa and 150 MPa squeezing pressures. All of the samples were subjected to thermal analysis involving temperature measurement at three different points and die surface using K-type thermocouples, data logger and infrared camera. Heat transfer coefficient between the molten metal and die was calculated under some assumptions and cooling curves were obtained. Beside temperature analyses, some mechanical tests were carried out. During machining the samples by lathe, a lot of chips were collected and machinability characteristics were investigated depending on chip lengths; and the Brinell hardness tests, surface roughness measurements and tension tests were done. For microstructural analysis, the scanning electron microscope investigation and metallographic observation were carried out. 28 SEM photographs were taken and 3 metallographic observation done to observe the microstructure properties depending on squeezing pressures. At result, it was found that, when the squeezing pressure was increased, the heat transfer coefficient between the molten metal and die and mechanic characteristics of cast samples were improved.