EFFECTS OF A MODIFIED SIMA PROCESS ON THE STRUCTURE, HARDNESS AND MECHANICAL PROPERTIES OF Al-۱۲Zn-۳Mg-۲.۵Cu ALLOY

A modified strain-induced melt activation (SIMA) process was applied and its effect on the structural characteristics and hardness of the aluminum alloy Al–۱۲Zn–۳Mg–۲.۵Cu was investigated. Specimens subjected to a deformation of ۴۰% at ۳۰۰ °C were heat treated at various times (۱۰-۴۰ min) and temperatures (۵۵۰-۶۰۰ °C). Microstructural studies were carried out using optical and scanning electron microscopies (SEM). Results showed that the best microstructure was obtained at the temperature and time of ۵۷۵ °C and ۲۰ min, respectively. The hardness test results revealed superior hardness in comparison with the samples prepared without the application of the modified SIMA process. T۶ heat treatment including quenching to ۲۵ °C and aging at ۱۲۰ °C for ۲۴ h was employed to reach to the maximum strength. After the T۶ heat treatment, the average tensile strength increased from ۲۳۱ MPa to ۴۸۷ and ۲۱۵ MPa to ۴۶۲ for samples before and after strain-induced melt activation process, respectively. Ultimate strength of globular microstructure specimens after SIMA process has a lower value than as-cast specimens without SIMA process

کلیدواژه ها:

Casting ، Heat treatments ، Microstructure ، SIMA process