The Research On WAl Intermetallic Compound Was Fabricated And Influence Of PCA On The Process Of The TiAl Solid-liquid Reaction Milling

A novel solid-liquid reaction milling technique was selected to prepare intermetallic compound powders by reacting the milling medium with molten metal at a certain temperature range. In the reaction milling course, some milling balls usually bond together which prevent the reaction between the balls and the molten metal. This paper selected the W, Ti as the balls, and Al metal as the liquid metal. The identification of different phases is analyzed by X-ray diffraction(XRD). The morphology and the microstructure of the as-formed powders is analyzed by scanning electron microscopy(SEM) and transmission electron microscopy(TEM).Firstly, W-Al alloy system was investigated. The phase formation regularities and the characteristics of the as-formed powders under different conditions during milling were studied. The conclusions are drawn as follows:(1) For W-Al system, W balls were adopted to mill Al melt, the weight ratio of ball-to-material was 14:1 and the rotation speed of miller was 80rpm. The powders composed of Al12W, Al5W and Al phases were obtained during milling at 953K for 6h. No residual Al liquid was detected after 24h milling and a mixture of Al12W and Al5W was obtained finally. Pure Al5W powder was obtained after milling 48h at 1023K. After 6h milling at 1163K, Al4W and Al2O3 were formed. With the time prolonged, the amount of Al2O3 impurity increased.(2) The process of W-Al reation milling was in accordance with collision-peeling model. With the temperature increasing, the melting point of the as-formed intermetallic compounds raised. In addition, the obtained powder was finer with a longer milling time. The particle size can reach nanoscale.Secondly, The solid-liquid reaction milling processing for Ti-Al system was investigated. The milling temperature was kept at 1033K and the milling time was 10h. C,NaCl,KCl,stearic acid and Na2SO4 was selected before milling as the process control agents(PCA) to prevent the bonding between the milling balls. The effects of the category and the content of the added PCAs on the milling process and milling products were studied. At the same time, the mechanism of action of the PCA during milling was explored. The conclusions are drawn as follows:(1) PCAs can accelerate the reaction process and increase the powders product and weak the bonding between the balls, the melt and the as-formed powders. Moreover, there were only little contamination resulted from the PCAs. Some PCAs could even prevent the contaminations from outside circumstances.(2) The category and content of the PCAs had different influences on the component and amount of the products. When 5% NaCl or 3% stearic acid was added, a large amount of powder was abtained. And the product was almost the pure Al3Ti intermetallic compound.(3) The addition of PCA can produce finer powders with uniform partical size. But over added PCA may pollute the products.