THE EFFECT OF HOT ISOSTATIC PRESSING ON THE MECHANICAL PROPERTIES OF AEROSPACE ALUMINUM CASTINGS

摘要

Aluminum castings offer a low-cost manufacturing approach for many rotorcraft components, because complex shapes can be cast net. However, the usage of castings for fatigue or flight-critical applications is limited because of concern over the internal integrity of the casting. Internal defects, such as porosity, can severely reduce the mechanical strength and fatigue life of the component. Hot Isostatic Pressing (HIP) has been used for decades to improve the internal integrity of titanium and nickel base cast alloys. This paper examines the metallurgical benefits provided by the HIP of aluminum cast structure, and compares the effectiveness of Densal II, a lower-cost proprietary HIP process, to traditional HIP. In this study, A357 sand cast and A356 investment cast materials were put through either a conventional aluminum HIP cycle or the proprietary Densal II HIP process. Results indicate a significant improvement in fatigue strength with the introduction of either HIP or Densal II processing.