Aging behavior and thermal treatment of aluminum alloy AA6061 refined by different grain refiner master alloys

摘要

Al-Mg alloys are excellent candidates for engineering light structure materials, and have great potential in automotive, high Performance defence and aerospace applications. The effect of grain refiner master alloys on the aging behaviour of aluminium alloys AA 6061 are investigated. The addition of grain refiner particles in AA6061 alloy does not change the aging sequence. However, the result showed that the grain refiner master alloys accelerated the aging kinetic and reduced the aging times compared to the non-grain refined alloy AA 6061. During the precipitation hardening of AI alloy 6061 at 175°C, the peak aging of AA6061 which was grain refined by Al5-Ti-1B occurs at 6 h and at 8 h for the non-grain refined AA6061. The effects of prior cold-work on the recrystallisation behaviour during annealing process was studied for AA6061 with and without grain refiner master alloys. Recrystallisation started early at 200°C for the alloys which were grain refined and at 275°C for that which was not grain refined. Full recrystallisation ended up at 350°C and 400°C for the grain refined and the non-grain refined AA6061, respectively. Thus, the recrystallisation starts early in the microstructure which contains coarse distribution of large particles of intermetallic phases TiAl_3, TiB_2 and β second phase. In recent years, aluminum alloys have attracted the attention of many researchers, engineers and designers as promising structural materials for automotive industry or aerospace applications. The first register of production of an Al-6000 alloy was in 1921 when the Al 6061 alloy was produced with levels of 1 wt.% Si and 0.5 wt.% Mg, that is one of the earliest aluminum alloy aged without copper [1].