Ageing Effect on Hardness and Microstructureof Al-Zn-Mg Alloys
Ageing Effect on Hardness and Microstructure of Al-Zn-Mg Alloys

Experimental results of the investigation on the hardness of two Al-Zn-Mg alloys Al-10.0 Zn-4.0 Mg and Al-8.5 Zn-3.0 Mg (wt pct)] aged in the temperature range 60 similar to 310 degrees C for different intervals of time from 1/4 h to 168 h are presented. Both the alloys were found to show identical behaviour of hardness with ageing time. Alloy with higher Zn and Mg content had higher hardness than the alloy with lower solute content. There were three ranges of temperature in which different types of precipitates formed and affected the hardness. Some of the grain boundaries were found to migrate and precipitate free zone has been observed.