Study On The Regional Control Of Spray Deposition Continuous Extrusion Hypereutectic Al - Si Alloy

Hypereutectic Al-Si alloy is the most common cast aluminum, which has a low thermal expansion coefficient, high wear resistance and anti-seize property. It has been widely used in many kinds of piston members. However, when hypereutectic Al-Si alloy was prepared by conventional cast, thick strips or bulk primary silicon appear. The primary silicon not only seriously fragments the continuity of the matrix, but also increases brittleness, and causes difficult cutting, which limits the widespread application of hypereutectic Al-Si alloy. The refinement of hypereutectic Al-Si alloy primary silicon has become very popular among researchers.Spray deposition is a good method for preparing high performance hypereutectic Al-Si alloy with refined primary silicon. However, the core of the process is to achieve the rapid solidification semi-solid deposited billet deposited into the narrow wheel groove. To solve the problem, a lot of trial and several test devices have been done in this paper. Control method are summarized in the continuing regional exploration, detailed research has:(1) Design and manufacture several flow controller, there is a four-roller controller reformed from the initially flow controller, a big copper rollers flow controller, a small four-roller flow controller, a small water-cooled four-roller controller, a double rotating disk flow controller and so on.(2) Analysis of the area controlled by different flow controllers, as well as the advantages of each structure. Having found the best flow controller is the copper rotating disk controller with water in it. And using the better thermal conductivity of copper disc and filled with water is not more prone to stick aluminum.(3) Twin rotating disk flow controller can obtain the desired narrow deposition billet, which has central width of10mm, total length340mm, the shape of the deposited billet matches with the groove of continuous extrusion machine.(4) When taking spray Conform test, the total utilization of twin rotating disk controller reaches18%, compared with the previous two-roller controller which has the material utilization less than1%, and7.1%by the big four-roller controller, and9.9%by the big copper four-roller controller, the material utilization has greatly improved.(5) Al-20Si was performed by spray Conform method with twin rotating disk flow controller, the microstructure of the material was greatly refined, the equivalent diameter of primary Si was3.4μm, sphericity1.2and dispersion factor was2.3μm. The tensile strength reaches204MPa, elongation is greater than6.8%, hardness value reaches101.4HRB.