Observations of the mechanical response and evolution of damage of AA 6061-T6 under different strain rates and temperatures

Investigated in this paper is the mechanical and microstructural response of specimens cut from rolled AA 6061-T6 alloy subjected to uniaxial loading at different temperatures (25, 100, 200, and 300 °C) and strain rates (10-4, 10−3, 10−2, 10−1 s−1). It was found that the material exhibits a strain rate and temperature dependent behavior. Microstructure observations reveal grains elongated in the loading direction with the average grain size being independent of loading conditions. However, it was observed that loading conditions influence the distribution and shape of the intermetallic phase particles. Micro cracks are observed to occur and are linked to observed damage and, consequently, decrease of ductility. Investigating the root cause of this damage mechanism reveals that particles of intermetallic phase composition are the likely sites of crack initiation. The crack-initiation mechanism at temperatures less than 200 °C is identified as crack initiation emanating from these particles while at temperatures of about 300 °C the mechanism is identified as interfacial decohesion.