Heat Treatment of a Slurry Squeeze-Cast ZA-27 Alloy at 150 °C

Abstract

This work reports the result of heat treatment on microstructures and mechanical property of ZA-27 zinc alloy gear part produced by a slurry squeeze casting process. The Gas Induced Semi-Solid (GISS) technique was employed for preparation of the alloy slurry. The microstructures and mechanical property of the alloy were studied by X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM) and HRB hardness testing. The specimens were solid solution heat treated at 365 °C for 1 h and artificially aged at 150 °C for 0.5, 1, 3, 6, 12 and 24 h. The as-cast microstructures of the alloy mainly consist of globular primary α phase surrounded by β,η and ε phases. After solution treatment the primary α and η phases were dissolved and transformed to the supersaturated β phase. At the early stage of ageing (0.5 – 3 h) the β phase decomposed to α and η phases. After a long period of ageing (6 – 24 h) α and ε phases decomposed through the transformation reaction: α + ε →T’+η. The hardness of specimens was increased after ageing for 0.5 h and gradually decreased with increasing ageing time. The peak hardness was 82 HRB at 0.5 h ageing. The hardness decreased to 62 HRB after ageing for 24 h.

Creep of Slurry Squeeze-Cast ZA-27 Zinc Alloy with Different Solid Fractions at 140 °C

“…The GISS technique can be used for casting many alloys, such as aluminum alloys, tin alloys, and zinc alloys. Recently, GISS technique was used for casting ZA-27 alloy gear part [9]. Creep is an important mechanical property of metals and alloys when they are used at high temperature and stress.…”