The study on characteristics of heat treatment of the direct squeeze cast 7075 wrought Al alloy

The 7075 wrought Al alloy (Al-5.7 wt.% Zn-1.7 wt.% Cu-2.6 wt.%Mg) was prepa red using the direct squeeze casting process in order to study the characte ristics of heat treatment. The micro-structures of squeeze casts applied wi th 25, 50 and 75 MPa could be free from the defects that occur with non-pre ssurized (gravity) die cast billets and became more refined and dense than those of non-pressurized casts. The hardness of 7075 alloy aged at 120 and 180 degreesC was increased with increasing applied pressure due to the incr ease in the nucleation site of intermediate precipitates. The heat resistin g property of 7075 Al alloy was improved by squeeze casting because of grai n refinement effect. In case of 120 degreesC for 129.6 h ageing treatment, the wear loss amount of squeeze cast was decreased as compared with non-pre ssurized casts, because of a high density of precipitates, fine grained str uctures and uniform distribution of eutectics in the periphery of grain bou ndary due to a reduction in solidification time. (C) 2001 Elsevier Science B,V. All rights reserved.