The Quality Control Of The Al Alloy Castings With High Performance

Cast aluminum alloy is one kind of traditional metal materials, which is widely used in many fields such as aviation, spaceflight, automobile, mechanism etc because of its low denstiy and high specific strength. With the development of modern industry and new casting technology, the demand for Cast aluminum alloy becomes larger and larger. The defects of aluminum castings such as gas hole, inclusions and crack, etc, impair the quality of products of aluminum alloy, especially when aluminum alloy is used to make high-performance castings. In this paper, in view of the characteristics of Cast aluminum alloy, the modification of aluminum melt, grain refinement over the surface of aluminum alloy castings, the analysis of the reason for crack in ZL201 aluminum alloy castings have been systematically studied in order to enhance the performance of the aluminum alloy castings. The Sr modification technology in ZL102 aluminum alloy, the fading of Sr modification and its effects on the pin-hole have been studied. The result shows that the appropriate control of the adding amount of Sr and the holding time can effectively improve the quality of aluminum alloy liquid, meanwhile it decreases the pin-hole and the trend of hydrogen absorbing. The difficult problem of the poor quality of aluminum melt under the condition of high amount, long holding time, and the mass production has been solved. When the holding time ranges from 60 min to 90min,the effect of the modification is the best ,and the class of pin-hole is grade 1. At that time the sound casting can be achieved. The law of the fading of the Sr can be induced: 1/C_Sr=3.2t+147. The coating containing La₂O₃+Sb,Sb+TiN used in the grain refinement of the surface of the castings has been developed. The results demonstrate that it can change the original phase-αfrom 22.5μm long, 9.1μm wide to 12.25μm long and 4.10μm wide.The thickness of the grain refinement layer is up to 1mm. The reason for the crack of the ZL201 alloy castings has been systematically analyzed. The porposed measures to eliminate the cracks of AlCu alloy are applied to mass production. It is understand that the effect of Si content on the crack of ZL201 alloy castings has been researched. When the amount of Si exceeds 1.0%, there are a lot of phases of CuAl2 and original phases of AlCuMn distributed along with grain-interface, which directly result in the defects of the crack of the ZL201 alloy castings.