The casting process performance of aluminum alloys is generally understood as a combination of those properties that are most prominent during the filling mold, crystallization, and cooling process. Fluidity, shrinkage, air tightness, casting stress, air absorption.
1. Activity
Activity refers to the ability of alloy liquid to fill the mold. The size of the activity determines whether alloys can forge large castings. Eutectic alloys in aluminum alloys exhibit the best activity.
There are many factors that affect activity, the important being identity, temperature, and the presence of solid particles of metal oxides, metal compounds, and other pollutants in the alloy liquid. However, the external fundamental factor is the roughness of the pouring temperature and pressure (commonly known as the pouring head).
In real production, in an environment where the alloy has been determined, in addition to strengthening the smelting process (essence and slag removal), it is also necessary to improve the casting process (sand mold permeability, metal mold exhaust gas, and temperature), and improve the pouring temperature without affecting the quality of the casting, ensuring the activity of the alloy.
2. Contractility
Shrinkage is one of the main characteristics of cast aluminum alloys. Generally speaking, alloys can be divided into three stages from liquid pouring to solidification, and then to cooling to room temperature, namely, liquid shrinkage, solidification shrinkage, and solid shrinkage. The shrinkage of alloys has a decisive impact on the quality of castings, which affects the size of shrinkage cavities, the generation of stress, the formation of cracks, and the change in size of castings. Generally, casting shrinkage is divided into volume shrinkage and linear shrinkage. In practical production, linear shrinkage is commonly used to measure the shrinkage of alloys. The shrinkage of aluminum alloys, usually expressed as a percentage, is called shrinkage.
