Structure-property correlation in Al–Zn–Mg alloy cast developed through in-situ microwave casting

Abstract

Casting is one of the preferred routes to manufacture net shape parts. Major concern in this process is to obtain suitable microstructure in the cast parts and thereby achieving desired mechanical properties. Recently, a new approach in metal casting called ‘in-situ microwave casting’ (MWC) has been reported in which microwave energy is used during melting, pouring and solidification of the cast material. The complete process is carried out inside the applicator cavity which adds more flexibility due to control over the mold temperature and solidification inside the applicator. In the present work, some studies/analysis on microstructure and mechanical properties of the developed in-situ microwave casts of aluminum 7039 alloy has been presented. The alloy was cast in-situ in an ambient atmosphere inside a microwave applicator using microwave energy at 2.45GHz and 1400W. Characterization of the in-situ casts was carried out to study the grain structure, phases and their distribution, porosity and mechanical properties. A dense cast was obtained with porosity less than 2%. The in-situ cast consists of MgZn2, Mg2Si, Al3Fe and Al8Fe2Si precipitates and intermetallic phases. Ultimate tensile strength (UTS) of the in-situ microwave cast was observed to be 148.46±10MPa and the average micro indentation hardness was observed higher near the gain boundaries (maximum 132HV) than inside the α-Al grains (maximum 120HV).