Microwave sintering process was employed to agglomerate ferromanganese alloy powders. The effects of sintering temperature, holding time and particle size composition on the properties and microstructure of sintering products were investigated. The results was shown that increasing sintering temperature or holding time appropriately is beneficial to increase the compressive strength and volume density. SEM and EDAX analysis shows that the liquid phase formed below the melting point in the sintering process, which leads to densification. XRD patterns indicate that the main reaction during microwave sintering is the decarbonization and carburization of iron carbide phase. The experiment demonstrate that the optimum microwave sintering process condition is 1150°C, 10 min and 50% content of the powders with the size of –75 μm

439L stainless steel composites blended with fifteen micron SiC particles were prepared by uniaxial pressing of raw powders at 100 MPa and conventional sintering at 1350oC for 2 h. Based on the results of X-ray diffraction analysis, dissolution of SiC particles were apparent. The 5 vol% SiC specimen demonstrated maximal densification (91.5%) among prepared specimens ­(0-10 vol% SiC); the relative density was higher than the specimens in the literature (80-84%) prepared by a similar process but at a higher forming pressure (700 MPa). The stress-strain curve and yield strength were also maximal at the 5 vol% of SiC, indicating that densification is the most important parameter determining the mechanical property. The added SiC particles in this study did not serve as the reinforcement phase for the 439L steel matrix but as a liquid-phase-sintering agent for facilitating densification, which eventually improved the mechanical property of the sintered product.

Ultrasound-promoted transient liquid phase bonding (U-TLP) is a high quality, high efficiency, and low-cost method for fast bonding of difficult-wetting materials in the atmospheric environment. In this paper, U-TLP was used to bond SiC particles reinforced aluminium-based metal matrix composite which particle volume fraction was 70%. The pure zinc foil was used as the intermediate layer. The effects of ultrasonic on microstructure evolution and mechanical properties of joints during the transient liquefaction stage were investigated. The mechanism of ultrasonic effects in the transient liquefaction stage of U-TLP was also inducted. The results showed that high volume fraction SiCp/Al MMCs were bonded well at low temperature in the air environment. Ultrasonic vibration can remove the oxide film on the surface of aluminum matrix composites, enhance the wettability of SiC particles with weld metal, promote atomic diffusion and homogenization of SiC particles, and improve the welding quality and efficiency. Reasonable increase of ultrasonic vibration time could effectively improve the joint strength.