Final treatment of aluminium castings: HIP and heat treatment united into a new process

摘要

Aluminium castings are increasingly used in applications requiring a maximum degree of mechanical strength. In the manufacture of automobiles, steel or cast iron components are replaced by lightweight aluminium castings in order to reduce fuel consumption and harmful emissions. The mechanical strength of a casting is first of all determined by the material used and by its structure. However, structural defects caused by conventional casting procedures, such as gas pores, shrinkage cavities and non-metallic inclusions, limit its performance potential, in particular in case of dynamic load (fatigue fracture). Appropriate treatment of the melt and turbulence-poor mould filling result in a reduction of nonmetallic inclusions. But the formation of gas pores and shrinkage cavities caused by hydrogen is very difficult to control, and in general not avoidable, because of the complex solidification mechanism.