Low- and High-Pressure Casting Aluminum Alloys: A Review

Abstract

Low- pressure casting and high-pressure casting processes are the most common liquid-based technologies used to produce aluminum components. Processing conditions such as cooling rate and pressure level greatly influence the microstructure, mechanical properties, and heat treatment response of the Al alloys produced through these casting techniques. The performance of heat treatment depends on the alloy’s chemical composition and the casting condition such as the vacuum required for high-pressure casting, thus, highlighting the low-pressure casting application that does not require a vacuum. The level of pressure applied to fill the mold cavity can affect the formation of gas porosities and oxide films in the cast. Moreover, mechanical properties are influenced by the microstructure, i.e., secondary dendritic arm spacing, grain size, and the morphology of the secondary phases in the α-matrix. Thus, the current study evaluates the most current research developments performed to reduce these defects and to improve the mechanical performance of the casts produced by low- and high-pressure casting.

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

“…The shock towers did not show any defects caused by pre-solidification or shrinkage porosity, which are mainly caused by high temperature differences in solidification; this was a main concern due to the low percentage of silicon and the high temperature set up at the dosing furnace, as shown in Figures 8 and 9. The main defects detected in the mechanical property's samples were small porosities generated due to the process [20][21][22][27][28][29][30][31].…”

“…The advantage of Aural TM -5 compared to other aluminum alloys used for structural components in HPDC is the elongation percentage that can be obtained without the application of heat treatment, even within the same families of Aural alloys, as shown in Table 1. However, the quantity of silicon added to the aluminum alloy depends on the casting process; in the case of HPDC, due to the high solidification rate, it is required to have a per-centage between 8 and 12%, since it increases the melt fluidity and decreases the coefficient of thermal expansion, facilitating the casting and improving mechanical properties [22]. The lower silicon content reduces the melt fluidity, which is critical for the injection process.…”

The Potential of Cast Stock for the Forging of Aluminum Components within the Automotive Industry

“…Notably, the surface segregation depth in LPC billets is significantly lower compared to those billets produced with traditional casting technologies [16]. Nunes et al [23] provide a comparative analysis of low-and highpressure casting technologies, highlighting the reduced tendency of defect formation in lowpressure casting technologies. While LPC material has primarily found application within extrusion, reportedly increasing yield and productivity [24], its potential in aluminum forging remains unexplored despite the improved quality and available dimensions.…”