Effect of Local Pressurization on Microstructure and Mechanical Properties of Aluminum Alloy Flywheel Housing with Complex Shape

Abstract

In this work, squeeze casting experiments of flywheel housing components with a large wall thickness difference and a complex shape were carried out with AlSi9Mg aluminum alloy. The defects, microstructures, and mechanical properties under different process parameters were investigated. Furthermore, the local pressurization process was applied to the thick-walled positions to force-feed the cast defects. The mechanical properties and microstructures at these positions were analyzed. The results showed that the surface quality of formed components was good and that local pressurization could effectively reduce the shrinkage cavity and shrinkage porosity in thick walls, but the scope and effect of forced feeding were limited. The optimum process parameters were a pouring temperature of 650 °C, a specific pressure of 48 MPa, a mold temperature of 220 °C, a local pressurization of 800 MPa, and pressure delay times of 15 s (side A) and 17 s (side B). The ultimate tensile strength, yield strength, and elongation of the formed component under validation experiments of the optimum process parameters were 201 MPa, 103 MPa, and 5.1%. Meanwhile, the fine grains of primary α-Al were mainly rosette and equiaxed grains, and the average grain size was about 40 μm. The microstructure of the eutectic silicon was acicular and was prone to segregation under pressure. According to profile morphology, the positions after pressurization were divided into a deformation zone, a direct action zone, and an indirect action zone. The coexistence of as-cast and plastic deformation microstructures was observed. The effect of local pressurization mainly involved a change in the solidification process, plastic deformation, and forced feeding.

Mechanical Properties of a Structural Component Processed in High-Pressure Die Casting (HPDC) with a Non-Heat-Treated Aluminum Alloy

“…These materials are typically applied in structural components in a vehicle, and they have the capability of satisfying the current demands of being economically sustainable and the mandatory requirement of having more efficient mechanical performance, therefore reducing the vehicle's weight and fuel consumption, and contributing to the reduction in CO 2 emissions, not only in their products but also during their manufacturing processing [6][7][8]. This is a reason why these aluminum alloys began to be widely applied in automotive structural components besides their superb mechanical and physical characteristics such as good rigidity, strength to weight ratio, and corrosion resistance performance [9]. However, most of these material alloys require a heat treatment process to obtain the desired characteristics and attributes suitable for specific applications [10], particularly mechanical performance.…”

“…On the other hand, novel casting technologies for manufacturing larger components, such as high-pressure die casting (HPDC), have emerged with improved material properties and characteristics that allow aluminum alloys to meet strict industrial requirements and substantially reduce the weight of automotive parts or components [11]. Furthermore, high-pressure die casting is considered one of the most profitable and productive processes in casting components [9], due to its ability to enable the mass production of a wide variety of components [12]. Generally, it is a process with great repeatability, where molten aluminum can be injected into a steel die under high pressures at a high speed.…”