Recent studies have shown that metal powder compacts can be heated to high temperatures using microwaves. While microwave heating of ceramics is well understood and modeled, there is still uncertainty about the exact mechanism and mode of microwave heating of particulate metals. The current study describes an approach for modeling the microwave heating of metal powder compacts using an electromagnetic-thermal model. The model predicts the variation in temperature with time during sintering. The effect of powder size, emissivity, and susceptor heating on the heating rate has also been assessed. These predictions have been validated by the experimental observations of the thermal profiles of Sn-, Cu-, and W-alloy compacts, using a 2.45 GHz multimode microwave furnace.

This paper is a critical review of dynamic compaction as a means to densify metal powders. Dynamic compaction was discovered in the 1960s. Most of the investigations since then have focused mainly on the physics dealing with energy, motion and force aspects of the process. Owing to this, there is a lack of knowledge of the effects of preprocessing and processing factors on this process. This knowledge gap has created skepticism in the PM community about this process' practice. This review attempts to bridge this gap and highlights the powder metallurgical aspects of dynamic compaction by emphasising the key powder related factors and processing parameters affecting dynamic compaction. Powder related factors include powder characteristics and the processing parameters including the machine operating parameters. Attention has been given to iron, aluminium and copper powders. Through this review, this article paves the way to design of high density dynamic compaction systems based on the final PM component requirements, by adjusting the material and processing parameters.

The aim of the present investigation is to study the sintering behavior of the Cu-12Sn bronze system in both, a microwave furnace as well as a conventional furnace. The powders prepared by premixed and prealloyed routes were sintered in the range of solid state, transient and supersolidus liquid phase sintering conditions. The comparative analysis is based on the sintered density, densification parameter, hardness, macrostructures and microstructures of the samples

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Compaction to full density is a means to deliver performance and precision without the distortion associated with sintering densification. High strain rate compaction using shock waves has been demonstrated as one means to attain full density in the green state. In the present study, variations in the compaction pressure are used to determine the conditions for attaining full density and these conditions are compared between high velocity and traditional die compaction technologies. A diminishing effect of compaction pressure on densification was observed. At the same compaction pressure the green density and hardness were lower using high velocity compaction. Sound velocity measurements in the powder show high velocity compaction did not generate a shock wave. Therefore, under subcritical compaction velocity conditions there is a higher green density from conventional compaction when compared using the same peak pressure.

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