Hardenability of high strength 7055 aluminum alloy thick plate

The hardenability of high strength 7055 aluminum alloy thick plate was studied by end quenching test, the microstructure was investigated by means of optical microscopy, scanning electron microscopy and transmission electron microscopy. The results show that the hardened depth is about 45mm for the plate and the corresponding cooling rate is about 230℃/min. A number of equilibrium phase particles tend to form on dispersoids and at grain boundaries after slow quench. The lower the cooling rate, the more the quench-induced phase, the fewer the η´ strengthening precipitates after aging and the wider the precipitate free zone near grain boundaries. In the range of the studied cooling rates, there is a linear relationship between hardness, width of precipitate free zone near grain boundaries and logarithm of cooling rate.     

Key words: hardenability;7055 aluminum alloy plate; end quenching; hardness; microstructure