Effects of Two Stages of Electro-Magnetic Stirring on Microstructural Evolution in Rheo-Diecasting of a Near Eutectic Al^|^ndash;Si Alloy

Abstract

A new slurry-making method consisting of two-stages of electro-magnetic(EM) stirring, was developed to manufacture high-quality slurries for rheo-diecasting of a near eutectic Al-Si based piston alloy. In the 1 st stage of EM stirring, the optimized process conditions, such as the pouring temperature and the EM induction intensity were investigated to control the microstructural evolution of the primary Si particles. The 2 nd stage of EM stirring was carried out to obtain fine and uniform globular α-Al particles and intermetallic compounds. High quality slurries with fine and uniform microstructures for rheo-diecasting can be obtained through the two-stages of EM stirring. Mechanical properties, such as hardness, high temperature tensile strength and relative wear resistance were evaluated on the specimens taken from the rheodiecast products, and the results are compared with those of the conventional metal mold cast piston.

Effect of Casting Parameters on the Microstructure and Mechanical Properties of ADC10 Alloys Using a Semisolid Die Casting and Heat Treating Process

“…At lower pouring temperatures, the ¡-Al particles become smaller and globularity increases. 8,9,13) Therefore, 873 K (605°C) was found to be the optimal pouring temperature to ensure a uniform and fine semisolid slurry for die casting. Thus, further experiments were performed to explore other casting parameters at the optimal pouring temperature of 873 K (605°C).…”

“…Figure 10 semisolid die cast specimens showed no micro porosities. 8) In addition, the constitutional distribution of Si has an effect on the precipitation. Long and rectangular Si particles hinder the movement of solute diffusion for clustering, which also reduces the mechanical properties that arise from heat treating.…”

“…12,13) In the semisolid casting of ADC10 alloy, compared to other Al-alloys, the relatively small difference between the liquidus and solidus makes it difficult to obtain a high quality semisolid slurry. Past work by Hong and Kim on the semisolid die casting of ADC10 alloys have been presented, 8,14) wherein the effects of lower pouring temperature and conditions of the slurry-making container was discussed. However, the detailed casting parameters such as the cooling rate, container thickness and temperature, and temperature distribution along the container have yet to be fully understood.…”