Er on the A356 alloy semi-solid cast

Title: Er on the A356 alloy semi-solid cast and the metamorphism of Author: Zheng Xuebin Degree-granting units: Beijing University Keywords: Er;; A356 alloy;; semi-solid;; deterioration Summary: Semi-solid forming (SSM) is superior to conventional liquid-solid metal forming and metal forming of near net shape technology. Hypoeutectic Al-Si alloy in the primary α-Al phase and the eutectic silicon phase determines the size and morphology of semi-solid forming parts of the final performance. In this paper, optical microscope, quantitative metallographic analysis, X-ray diffraction, thermal analysis, scanning electron microscopy and transmission electron microscopy and other analytical tools for study of rare earth Er A356 hypoeutectic Al-Si alloy semi-solid cast and metamorphism, the results show that: Er-cast A356 alloy can reduce the secondary Neodymium magnets dendrite arm spacing (DAS), grain refinement of cast, so that tends to equiaxed dendrite oriented. Increase of Er added heterogeneous nucleation, the semi-solid structure of primary α-Al phase percentage increases, increasing the α-Al phase solidification range, broadening the temperature range of two-phase region, lower semi-solid slurry preparation the temperature requirements, saving the cost of process control. Morphology of eutectic silicon phase change can improve the mobility of semi-solid slurry. Er eutectic silicon phase of a significant modification effect, add 0.3% of Er can make the eutectic silicon sheet by the thick needle into a small fibrous. Deterioration of Er has a critical cooling rate, the modification effect of cooling rate increases with the increase. As the Er can significantly reduce the total crystal nucleation and growth of the temperature, increase the eutectic recalescence temperature, nucleation difficult to make silicon eutectic Al grains prior to the nucleation of eutectic silicon, silicon eutectic phase Al was forced to only between grain nucleation, and thus the formation of fibrous forms. Control by adding rare earth Er grain nucleation and growth, can be prepared with a small, round ball of semi-solid slurry particles, slurry solid fraction in between 0 to 0.45. Semi-solid roundness of primary phase content increases with increasing Er, Er content increases to 0.5% of the roundness of the primary phase reaches its maximum value. Er solidification of the remaining liquid produced by the second primary α2-Al phase also has a great influence, to make http://www.chinamagnets.biz/Neodymium/Ball-Neodymium-Magnets.php primary α2-Al phase from the dendrites into small spherical crystal. Add 0.3% of the tensile properties of Er significantly improved, but continue to increase the content of Er, Er-rich alloy phase appears mainly to needle-like morphology and the massive presence of the alloys have an adverse effect. Therefore, the optimal dosage of 0.3% rare-earth Er. ALLOY system for the study found that in 180oC time 6h alloy for maximum hardness. Alloy in the aging process of strengthening the role of the still from the strengthening phase Mg2Si, Al-Er intermetallic compounds in the process increase the strength of the alloy is not. Degree Year: 2010