State-of-the-art in microwave processing of metals, metal powders and alloys

Discovery of the capacity of microwave energy to heat materials was a major milestone in the history of technology and scientific research. This discovery led to the development of many devices and processes that have replaced conventional heating methods, thereby reducing reliance on fossil fuels and reducing atmospheric CO2 emissions. Over the past two decades the use of microwave heating for processing of non-dielectric metals, metal powders alloys have increased markedly and includes sintering, melting, joining, cladding, drilling, and 3D printing. These developments have used a wide range of experimental procedures, and the use of microwave power has resulted in significant benefits over conventional heating methods. These benefits include a many-fold decreases in processing times and energy consumption, as well as improved microstructural characteristics and mechanical properties of the processed material. This review provides a comprehensive overview of the state-of-the-art of microwave processing of metals, metal powders and their alloys and focuses on important process parameters such as heating mechanisms, electromagnetic properties of metals, the factors affecting these parameters and applications to metal processing. Requirements for efficient metal processing using microwave power are presented including metal properties, microwave susceptors, insulators, ceramic containment structures and temperature measurement methods that all play roles in the development of microwave processing of metals and metal alloy materials. Current challenges and issues in equipment design parameters and various processing methods to facilitate commercial implementation of metal processing at larger scales are investigated.