Low Superheat Pouring Weak Electromagnetic Stirring The Preparation Of Semi-solid-state Al-30% Si Alloy Slurry Process Research

Hypereutectic Al-30%Si alloy prepared by traditional casting contains primary Si growing as the shape of batten. Concentrated stress at the head of this kind of primary Si as a result of circle stress, which will reduce the mechanics properties (S_b and d_s) a lot. Primary Si is a phase of high stiffness, which results in bad machining property. At the same time the uniformity of Al-30%Si alloy is low as a result of congregated Si particles, so the using property is badly affected. To improve the structure and properties of traditional casting Al-30%Si alloy and excavate fully its application potential and quicken its application in the materials of piston, aim at Al-30%Si alloy, this text designs the experimental apparatus by itself, then prepared semi-solid Al-30%Si alloy by combining low superheat pouring and low intensity electromagnetism stirring process.The DTA curve of Al-30%Si alloy indicated that the liquidus line temperature was 838 °C. After conventional Al-30%Si alloy sample poured at 838 °C, under which semi-solid samples were poured at low superheat temperature. Then the microstructure of prepared samples was compared and analyzed. To improve further the microstructure and properties of semi-solid Al-30% Si alloy, which was poured at low superheat temperature, was inflicted upon with low intensity electromagnetism stirring.And then the effect of poured temperature, electromagnetism stirring power and time on microstructure transformation and improvement in properties.Quantitative analyzed results derived from Image Tool of microstructure of prepared Al-30%Si alloy indicated that not only the average size of primary Si reduced from 138.8μm to 11.49μm owing to low superheat pouring and low intensity electromagnetism stirring, but also distributed equably in the substrate with a shape of nearly rotundity.The property testing results of stiffness, friction and abrasion, heat stabilization, σ_b and δ_s, indicated that, the properties of the stiffness increased 74.59%,the abrasion velocity reduced nearly an order, the heat expansion coefficient minished 22.16%, S_b heightened 46.91451MPa and d_s increased 7.86 multiple compared with conventional casting Al-30%Si alloy.The experiment and analyzed results indicated that semi-solid Al-30%Si alloy was successfully prepared by combining low superheat pouring and low intensityelectromagnetism stirring process with following characters: low collective, fine size and approximate spheroid primary Si distributed equably in the eutectic substrate. All the microstructure, mechanical and rheological property improved to a certain extent. The experiment results improved the application value of Al-30%Si, and provided some direction meaning for scientific research and actual production.