A6061 Powder Metallurgy Pressed Parts

Product Introduction

Aluminum matrix composites are heterogeneous mixtures based on aluminum and its alloys, reinforced by metal, non-metallic particles, whiskers, or fibers, and are widely used in aerospace, automotive, and other fields. Since the reinforcement can be added to the composite material matrix in any proportion by using the method, the reinforcement is also easy to form a more uniform distribution on the macroscopic scale, the sintering temperature is low, and the interface reaction is easy to control; at the same time, the performance and stability of the material are significantly better than those prepared by other methods, so the powder metallurgy method has become a commonly used process for the preparation of aluminum matrix composites.

Process steps for preparing composite materials by powder metallurgy

1. Mix powder

The general mixing methods include ordinary dry mixing, ball milling, and wet mixing. Among the three powder mixing methods, ordinary dry mixing and wet mixing are prone to uneven distribution of reinforcements and a large number of agglomeration and layering. Ball milling is usually more commonly used and effective.

2. Powder pre-pressing

After the powder mixing is completed, the powder pre-pressing treatment is carried out. Powder pre-pressing methods mainly include cold pressing and cold isostatic pressing. In contrast, cold pressing is an economical and commonly used powder pre-pressing method. After the aluminum alloy powder is pre-pressed, the pre-compact density is generally required to be 70% to 80% of the composite material density to facilitate the escape of gas during the degassing stage. Since aluminum powder and reinforcements are easy to absorb water vapor and oxidize, the powder green body will release a large amount of water vapor, hydrogen, carbon dioxide, and carbon monoxide during heating. Therefore, the green body should be degassed before hot processing to avoid air bubbles and cracks in the product; the degassing temperature should generally be equal to or slightly higher than the subsequent hot pressing, hot processing deformation, and heat treatment temperature to avoid bubbles and delamination in the material caused by residual water and gas in the compact. However, if the temperature is too high, some other elements in the aluminum alloy may be burned, and the intermetallic compounds that play a strengthening role in the alloy will aggregate and coarsen, reducing the performance of the material.

3. Curing

After the powder has been degassed, it is densified, ie sintered, hot pressed, hot isostatically pressed, and hot pressed loose powder or pre-pressed powder. In the case of ensuring low cost and high productivity, the billet is formed by uniaxial cold extrusion, after degassing, it is raised to a certain temperature at a certain rate, and hot extruded according to a certain extrusion ratio, and then the final heat treatment is carried out to obtain the final material. This powder-forming process that combines powder metallurgy with subsequent densification treatments (such as extrusion, rolling, etc.) enables the powder to undergo plastic deformation under short-term high temperature and high pressure and then realizes the bonding between powder particles. Compared with the conventional powder metallurgy method, in addition to the three-dimensional compressive stress, the powder particles also bear a huge shear force along the extrusion direction during the extrusion process. The bond strength between adjacent powder particles is further enhanced after the oxide film on the surface is broken. Compared with the high-cost hot isostatic pressing process, the specific process of preparing composite materials by powder metallurgy includes the following steps.

Metal Injection Molding Process

Detection Systems