Masataka Sugiyama

Some properties of wrought high aluminium-zinc Base alloys affected by aluminium content

High Al-Zn alloys and Al-Zn-1%Cu alloys containing 20-50%Al were hot-rolled at 300-400°C, finally cold-rolled to 0.5mm thickness and subsequently solution-treated at 370°C for 2hr. The change of some properties of these alloys during ageing at room temperature, 150°C and 230°C for up to 4 months was studied, mainly as a function of Al content.The main results obtained are as follows: 1) Al content for wrought high Al-Zn alloys is desired to be less than 40%, concerning their workability and ductility after ageing. 2) Hardness and strength of the alloys increase with increasing of Al and of course with Cu content, but ductility decreases. 3) Ageing rate becomes maximum at 150°C among three ageing temperatures, and is remarkably affected by Alcontent and Cu addition especially in the case of room temperature ageing, namely, the rate at room temperature decreases by about 1/10 with every 10% increase of Al content in straight alloys. 4) Some countermeasures to check the unstability of these wrought alloys should be taken as in the case of casting alloys. 5) Mechanical properties of the aged wrought alloys are superior to those of casting alloys. 6) Structures of wrought alloys show much homogenious and this is thought to explain the fact that the ductility of the wrought alloys is higher than that of casting alloys. The change of microscopic structure of each alloy corresponds to the change of properties during ageing.