Investigation Of Quench Sensivity And Microstructure Of6082and6061Aluminum Alloys

6082and6061aluminum alloys are widely used for the appli-cation of construction, transportation and shipbuilding due to its average strength, excellent corrosion resistance, welding performance and good formability. However, the development of complex cross-section profile is restricted by its high sensitivity. In this paper, quenching characteristic was acquired via end quench test and interrupted quenching method. The correlation of performance with quenching rate was established, which could provide guidance in on-line quenching process.Using end quench test, the quench depth value (at10%reduction of hardness in T6condition is defined as quench depth value) of6082and6061aluminum alloy can reach15-20mm and20-25mm respectively. The simulated time-temperature-transformation (TTT) curve is well with the obtained time-temperature-property (TTP) curve. The (3-Mg2Si phase nose temperature of TTT curve of6082and6061is about450℃and440℃, similar of that β" and β’ phase is340℃and350℃separately. In order to ensure higher mechanical properties and low residual stress, the cooling rate of6082and6061aluminum alloy at the quench sensitive temperature range should be at15℃/s and10℃/s respectively. It should slow down properly in high and low temperature range.When the average cooling rate was about20℃/s, small and dis-persed strengthening precipitates formed and PFZ was narrow after artifi-cial aging; while the cooling rate slowed down to3℃/s, the quench in-duced precipitates as well as width of precipitate-free-zone (PFZ) in the as aged alloys increased and the volume of age harding phases declined, which giving rise to the reduction of hardness.By interrupted quenching method, when the alloys were preserved at high temperature, the precipitation of β-equilibrium phase was not ob-vious which retained high saturated solid solution and had small effect to aging; while in the isothermal process of medium temperature, quench induced precipitates formed and grew up quickly, leading to the decrease of element significantly which greatly affected age hardening. When the alloy was heat treated at low temperature, quench induced precipitates formed slowly but grew up with the extension of time. Combined with TEM analysis, heterogeneous precipitate β-Mg2Si is prior to nucleate on the (AlFeSi) dispersoids in the slow cooling and isothermal process which is a part reason of alloy’s high quench sensitivity.