Effects of non-isothermal aging on microstructure, mechanical properties and corrosion resistance of 2A14 aluminum alloy

Abstract

Abstract The microstructure, mechanical properties and intergranular corrosion (IGC) resistance of 2A14 aluminum alloy subjected to several non-isothermal aging (NIA) treatments have been investigated. When target aging temperature is 210 °C during NIA, the hardness at the heating rate of 10 °C/h are higher than that at the heating rate of 20 °C/h. A slight decline of hardness occurs when the temperature is beyond 200 °C during the heating stage of NIA process, while the hardness turns its step to improve at approximately 140 °C at the cooling stage. This is due to the mutual competition between the coarsening of precipitates and secondary precipitation during the cooling process. Compared with isothermal peak (T6) aging temper, The NIA process ((40–210, 10 °C/h) + (210–180, 20 °C/h)) makes the elongation and impact toughness of 2A14 aluminum alloy increase by 6.5% and 4.4%, respectively, while yield strength and fracture strength remain about the same. The co-precipitation of θ′ and Q′ precipitates can be observed for various aging conditions, but different from T6 aging, the NIA process leads to the high-density θ′ precipitates with wider length range. This characteristic of θ′ phase contributes to better mechanical performance of 2A14 aluminum alloy after the NIA process. In addition, the IGC resistance of the non-isothermal aged 2A14 alloy slightly decreases compared with that after T6 aging, which is closely linked with the widening of PFZ and the increase of potential difference between the PFZ and the matrix after the NIA process.