Powder Metallurgy Aluminum Alloys: Process, Densification, and Heat Treatment

We have attempted to produce components using aluminum alloy powders, and related literature indicates that their main advantage lies in achieving fine microstructures and complex shapes that are difficult to obtain through traditional casting or forging. In terms of design and manufacturing, the net-shape capability of powder metallurgy allows parts to be directly formed in the die, minimizing the need for extensive machining. For complex geometries, this not only reduces costs but also ensures dimensional accuracy. Regarding sintering furnaces, aluminum alloy powders are prone to forming surface oxide films; however, pressing can help break these oxide layers, while liquid-phase sintering mechanisms in aluminum-magnesium alloys promote densification. Inert atmospheres (such as nitrogen or argon) or vacuum sintering furnaces must be used to avoid oxidation and ensure good metallurgical bonding. In some cases, degassing or the addition of small amounts of magnesium is required before sintering to disrupt oxide films and enhance density. The characteristics of powder metallurgy aluminum alloys include low density, high specific strength, and good thermal conductivity. By adjusting alloying elements, properties such as wear resistance and high-temperature strength can be tailored. Compared with cast materials, powder metallurgy aluminum alloys exhibit finer grains and more uniform elemental distribution, resulting in superior mechanical properties and dimensional stability, making them suitable for aerospace, automotive, and electronic applications that demand lightweight and high strength.

During compaction, porosity is inevitably introduced into powder metallurgy aluminum alloys. If used directly after sintering, the density is often insufficient for high-strength applications. Therefore, secondary pressing, repressing, or cold forging is commonly employed to further increase densification. This process effectively compresses residual pores, yielding a more uniform microstructure, improved mechanical performance, and enhanced dimensional stability, particularly in terms of tensile strength and fatigue life. Literature reports indicate that density can be increased to above 99% after secondary pressing. For aerospace and automotive parts, powder metallurgy aluminum alloys subjected to secondary pressing can achieve properties close to wrought alloys, and when combined with subsequent heat treatments, they demonstrate even greater engineering value.

Aluminum alloys are often subjected to solution and aging treatments to maximize their performance. During solution treatment, the alloy is heated to a high temperature so that alloying elements dissolve fully into the aluminum matrix, followed by quenching to retain a supersaturated solid solution. Artificial aging is then performed by reheating at intermediate temperatures for an extended time, promoting uniform precipitation of fine phases throughout the matrix. This significantly enhances strength and hardness while maintaining adequate ductility. These treatments are among the main reasons aluminum alloys are widely adopted in aerospace and automotive industries.