热轧对7055铝合金淬透性的影响

Effect of hot rolling on hardenability of 7055 aluminum alloy

为研究热轧对7055铝合金淬透性的影响,采用末端淬火实验、硬度测试、光学显微镜和透射电镜研究了不同冷却速率处合金的组织和性能.实验结果表明:合金热轧后淬透性大大降低,淬透深度由约100 mm降至约45 mm,这主要与慢速淬火时析出的η平衡相的数量和尺寸的改变有关;热轧增加了η平衡相的形核位置,并引入大量的位错,增加了η平衡相的长大速率.因此,热轧合金固溶后慢速淬火时,析出的η平衡相的数量和尺寸都大大增加,时效后形成的η'沉淀强化相数量减少,硬度随冷却速率减小而下降的程度增加,合金的淬透性降低.

To investigate the effect of hot rolling on hardenability of 7055 aluminum alloy, the properties and mierostructure at different cooling rates determined by end-quench method, hardness test, optical microscopy and transmission electron microscopy were studied, and the results showed that the hardenability was decreased significantly after hot rolling with the hardened depth deceasing from about 100 mm to 45 mm. This is because the number and size of η equilibrium phase formed during slow quenching are changed by hot rolling. Hot rolling increases the nucleation sites for η equilibrium phase, and introduces a number of dislocations which prompt growth of η equilibrium phase. As a result, in the hotrolled and solution treated alloy, more η equilibrium phase particles with larger size are formed during slow quenching, which decreases the number of strengthening η precipitates after aging. Thus the drop in the hardness with the decreasing of cooling rate is increased, which decreases the hardenability.