Effect of Hot Isostatic Pressing on Microstructure and Mechanical Properties of Cast Aluminum Alloys-A Review

Hot isostatic pressing (Hipping) has over the years found many industrial applications in the broad field of Materials Manufacturing. One of these applications relates to the densification of metal castings. Castings based on aluminum alloys constitute an important segment of metal castings, where Hipping has found widespread usage. A number of cast aluminum alloys have been studied concerning the effect of Hipping on the quality of castings made of them. This review attempts a critical analysis of these studies. Drastic reduction in the volume fraction of porosity in the castings could be achieved by Hipping in a wide spectrum of cast aluminum alloys. There is substantial improvement in ductility and fatigue strength accruing from Hipping. Considering the poor ductility and low fatigue strength of these materials in the as-cast condition, Hipping makes a desirable proposition to the quality of these castings and make them suitable for a variety of applications. It appears, however, that if some unfavorable microstructural features such as oxides, coarse intermetallic particles, etc., dominate the starting material, the Hipping process may become ineffective or even counterproductive. There have been different studies aimed at combining Hipping and final heat treatment of cast AlSiMg alloys to reduce the manufacturing cycle time and thereby the cost of production. Such treatment prerequisites ability to realize fast cooling rates after solution treatment; there are constraints in this regard with the standard Hipping presses. There has been no focused and comprehensive review in the published literature of Hipping of cast aluminum alloys. This review is intended to bridge this gap; it also includes recommendations on further studies required.