THE EFFECTS OF RETROGRESSION PARAMETERS IN RRA TREATMENT ON TENSILE STRENGTH OF 7075 ALUMINIUM ALLOYS

In this study retrogression and re-aging (rra) treatments has been applied on 7075 aluminium alloys after t6 treatment. the alloys were retrogressed at various temperatures and times in the retrogression stage of rra treatment. the effects of the parameters mentioned above on tensile strengths and % elongations were investigated. besides fracture surfaces were examined by scanning electron microscopy (sem) for determination of the effects of retrogression temperatures and times on fracture mechanism. the alloy retrogressed at 220°c for 60 minutes showed the highest tensile strength values, on the other hand, the lowest elongation values. strong relationship has been seen between hardness and tensile strength; however, no effective relationship for elongation was available. retrogression temperatures and times affects on microstructure of the alloys, therefore, it has also great influence on the hardness and tensile strength, elongation and fracture mechanism.