Casting of aluminum alloys -Defects and part design

The quality of a cast part can be defined as its ability to satisfy the requirements specified in the customer's specifications. It depends on the design of the part by the client, and on the care taken in its production by the caster, who must master a large number of manufacturing parameters.

One of the keys to achieving this quality is to recognize and describe any anomalies or defects that may occur during the casting process, so that corrective action can be taken. Defects observed in aluminum alloy castings are similar to those encountered with other metals and alloys, though with some specific features, such as their high oxidizability in the liquid state and their tendency to dissolve hydrogen. These defects are examined in the first part of the article.

Part design must take into account the casting process used. The diversity of these processes in the case of aluminum alloys implies certain basic rules, the correct application of which is a prerequisite for obtaining quality parts. Digital techniques known as "virtual prototyping", which range from dimensional calculation to simulation of filling, solidification and cooling, enable improved part design and quality, as well as a significant reduction in costs and development times. This article describes the different types of defects and their origins, the means of repair, the design rules for avoiding them, and concludes with a discussion of numerical simulation of foundry processes, a major tool for rapidly achieving satisfactory quality.

The following articles complete the subject:

• [M 3 635] – Aluminium alloy melting ;

• [M 3 636] – Aluminum alloy casting. Sand, investment casting and visible processes;

• [M 3 637] – Aluminum alloy casting. Permanent molds: shell, die-cast and related.