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The present study investigates the effect of varying particle size and porosity on the heating behavior of a metallic particulate compact in a 2.45GHz multimode microwave furnace. Experiments on copper suggest that unlike monolithic (bulk) materials, metallic materials do couple with microwaves when they are in particulate form. The powder compacts having higher porosity and smaller particle sizes interact more effectively with microwaves and are heated more rapidly. A dynamic electromagnetic-thermal model was developed to simulate the temporal temperature distribution using a 2-D finite difference time domain (FDTD) approach. The model predicts the variation in temperature with time during heating of copper powder compacts. The simulated heating profiles correlate well with those observed from experiments

Refractory metals and alloys are well known for their high mechanical properties which make them useful for wide range of high temperature applications. However, owing to the refractoriness of these metals and alloys, it is very difficult to consolidate them under moderate conditions. Conventional P/M processing is a viable sintering technique for these refractory metals. One of the constraints in conventional sintering is long residence time which results in undesirable microstructural coarsening. This problem gets further aggravated when using smaller (submicron and nano) precursor powder sizes. Furthermore, conventional heating is mostly radiative, which leads to non-uniform heating in large components. This review article describes recent research findings about how these refractory metals and alloys (W, Mo, Re, W-Cu, W-NiCu and W-Ni-Fe) have been successfully consolidated using microwave sintering. A comparative study with conventional data has been made. In most cases, microwave sintering resulted in an overall reduction of sintering time of up to 80%. This sintering time reduction prevents grain growth substantially providing finer microstructure and as a result better mechanical properties have been observed.

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This study investigates the effect of heating mode on the sintering of tungsten-copper alloys containing up to 30 wt.% Cu. The sinterability of the W-Cu system consolidated in a 2.45 GHz multimode microwave furnace has been critically compared with that processed in a radiatively heated (conventional) furnace. The as-pressed W-Cu alloys can be readily sintered in microwave furnace with substantial (sixfold) reduction in the processing time. As compared to conventional sintering, microwave processing results in greater densification, more homogenous distribution of the binder phase, and smaller tungsten grain size. The densification in compacts increases with increasing Cu content. For all compositions, the electrical conductivity and hardness of microwave sintered W-Cu alloys are higher than those of their conventionally sintered counterparts. This study investigates the effect of heating mode on the sintering of tungsten-copper alloys containing up to 30 wt.% Cu. The W-Cu alloys were sintered in a 2.45 GHz microwave furnace with substantial (sixfold) reduction in the processing time. As compared to conventional sintering, microwave processing results in greater densification, more homogenous distribution of the binder phase, and smaller tungsten grain size. This results in higher electrical conductivity and hardness of the microwave sintered W-Cu alloys.

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