Double compound modification was carried out for hypereutectic Al-24Si alloy. The experiment showed that double modification with phosphorus and rare earth can fine the microstructure of alloy. The complex modifications of phosphorus and rare earth make the coarse block primary silicon obviously refined and the large needle eutectic silicon modified to the fine fibrous or lamella ones. The alloys with the additions of 0.10% P(phosphorus) and 0.90% RE(rare earth) have the optimal microstructure and the highest mechanical properties. Compared with the unmodified alloy, the primary silicon of alloys can be refined from 93.5μm to 24.1μm. The tensile strength is improved from 248MPa to 305MPa and the elongation is improved from 0.31% to 0.47%. Mechanism of double compound modification with phosphorus and rare earth is discussed as well.
Modification process of carbon fiber reinforcement was investigated so as to produce aluminum matrix composite on a large scale. A series of pretreatment technologies could acquire chemical deposition silver, which became the base of copperplating on the surface of carbon fibers. The optimum conditions of electroless plating copper, including components, adding amount of carbon fibers, temperature, pH value, and mixing method, were determined to obtain a perfect copper layer on the surface of carbon fibers. The control of copper deposition and repeating utilization of many technology solutions were realized to reduce the costs. The results laid a foundation of mass production for carbon fiber reinforced aluminum matrix composite.
Double compound modification was carried out for hypereutectic Al-24Si alloy. The experiment showed that double modification with phosphorus and rare earth can fine the structure of alloy. The complex modifications of phosphorus and rare earth make the coarse block primary silicon obviously refined and the large needle eutectic silicon modified to the fine fibrous or lamella ones. Phosphorus mainly refines the primary silicon. Rare earth can well refine the primary and eutectic silicon, but its modification effect on the eutectic silicon is more obvious. The alloys with the additions of 0.10% phosphorus and 0.9% rare earth have the optimal microstructure. Compared with the unmodified alloy, the primary silicon of alloys can be refined from 93.5 μm to 24.1 μm and the eutectic silicon can be refined from 8.5 μm to 5.3 μm. Mechanism of double compound modification with phosphorus and rare earth is discussed as well.
Education informationization of primary and junior school is the foundation and conditions for achieving the education modernization, It is the important content and main symbol of education modernization。This paper take Xinxiang city as an example, Through the analysis on the hardware and software facilities, teachers, information technology course,etc,to expound the difference between Urban and Rural during Educational Informatization of the Primary and Junior School, and submit corresponding resolving strategies.
In this study, the fabrication of the desired SPR joints was investigated as a function of the preheat temperature and strain rate. To determine the optimum preheat temperature, Gleeble thermal analogue testing of 2mm thick magnesium AZ31 was used to assess the combined influence of preheat temperature and strain rate on the strength and total elongation of magnesium AZ31. Magnesium alloy AZ31 with a thickness of 2mm was preheated with various temperatures prior to self-piercing riveting. The appearances, cross-sections and mechanical tests of the SPR magnesium AZ31 joints were investigated. It was found that a preheat temperature of 180 to 200oC largely eliminated the cracking in magnesium AZ31 joints. The joint strength increases with increasing preheat temperature from ambient to 200oC. The strength increase is attributed to the reduction in joint cracking and an increase in mechanical interlock between the rivet and work pieces.
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