Anticorrosive properties of borophosphate and boron-free enamels to molten aluminum were investigated using SEM and electron probe. Carbonates of alkali metal and alkaline earth metal were added in an appropriate weight ratio to achieve desired melting temperature of the enamels. SEM examination on the solidified interface between the enamels and aluminum alloy show that the enamels can spread slightly on aluminum alloy. For anticorrosive sample of borophosphate enamel, phosphorus was not detected by electron probe at the side of aluminum alloy near the interface, but silicon was detected in the silica-free enamels side. For the sample of boron-free enamels, however, phosphorus was found at the side of aluminum alloy near the interface. It was revealed that the enamels with high B2O3-P2O5 content have high corrosion resistance to molten aluminum.

The rotating impeller degassing technique was used for degassing of A356 scrap melt which had been protected and purified with an RE-containing JDN-I flux. Results indicated that the modification of eutectic silicon was faded and the mechanical properties of the alloy became worse after rotating impeller degassing and that the tensile strength and elongation of the scrap A356 alloy which was treated with rotating impeller degassing system after having been refined by JDN-I flux decreased by 5.6 and 23.3%, respectively, compared with those of being refined merely with the flux. The mechanism is that the rotating impeller degassing increases the oxygen content and decreases the hydrogen content of the melt, consuming more rare earth from the RE-containing lux. Thus, the content of rare earth that has effect on the modification of eutectic silicon is lower than the critical value. At the same time, the oxide inclusions in the melt increase leading to a drop of mechanical properties of the alloy.

Single-layered coatings of WC-Co and multi-layered coatings of NiCrAl/WC-Co were manufactured by high-velocity oxy-fuel (HVOF) and detonation spraying (DS) techniques. The residual stress, mechanical properties, and wear resistance of these coatings were evaluated and the effects of coating structure and spraying method on coating properties were analyzed. Experimental results show that the coatings made by HVOF excel corresponding DS coatings with respect to mechanical and thermal shock properties. Both the spraying method and coating structure affect the residual stress markedly. Compared with the single-layered coatings, multi-layered ones exhibit better wear resistance under light-load conditions.

Gelcasting, an in situ consolidation colloid forming process, is promising for the manufacture of structural ceramics with various shapes. In this case, the gelcasting process was adopted to obtain carbon artifacts with complex shapes. The mesocarbon microbead (MCMB) that has self-sintering property was chosen as the starting material. In order to optimize the MCMB suspensions for gelcasting, the zeta potentials of MCMB particles dispersing in water and the rheological behaviors of MCMB suspensions were investigated. A stable MCMB suspension with solid loading up to 62.5wt.% was prepared, from which uniform green body with complex shape was successfully gelcast. The performance of green bodies and sintered samples were measured and their microstructures were observed.

Various purification methods were explored to eliminate the dissolved hydrogen and nonmetallic inclusious from molten alu minum alloys. A novel rotating impeller head with self-oscillation nozzles or an electromagnetic valve in the gas circuit was used to produce pulse gas currents for the rotary impeller degassing method. Water si mulation results show that the size of gas bubbles can be decreased by 10%-20% as compared with the constant gas current mode. By coating ceramic filters or particles with active flux or enamels, composite filters were used to filter the scrap A356 alloy and pure alu minum. Experimental results de monstrate that better filtration efficiency and operation performance can be obtained. Based on nu merical calculations, the separation efficiency of inclusions by high frequency magnetic field can be significantly improved by using a hollow cylinder like separator or utilizing the effects of secondary flow of the melt in a square separa-tor. A multi-stage and multi-media purification platform based on these methods was designed and applied in on-line pro- cessing of molten aluminum alloys. Mechanical properties of the processed scrap A356 alloy are greatly improved by the composite purification.