A New Type Of Al-mg-si-cu Alloy During Hot Deformation Behavior Of Extruded Profiles For Heat Treatment Process

In this paper, the hot deformation behaviors of a new Al-Mg-Si-Cu alloy were studied first by means of compression deformation tests on Gleeble 1500 machine at strain rates ranged between 0.005⁵s^-1 and deformation temperature 350⁵50 ℃ ,and associated structural changes were studied by observations of metallographic and TEM. Then the heat treat process was studied on this new alloy by means of analysis and comparision on heat treated specimens which were treated through 5 different aging,quenching schedules after soluted at 550℃/2h.The results are shown as following:1) The true stress-ture strain curves of new Al-Mg-Si-Cu alloy exhibits a peak stress at small strain(<0.15), after which the flow stresses decrease monotonically until high strains,showing a dynamic softening. Peak stress will decrease if strain rate decreases or deformation temperature increases.2) Peak stress for new Al-Mg-Si-Cu alloy can be represented by the exponent—type equation with the hot deformation activation energy of this alloy is 236 kJ/mol.3) Besides DRV, DRX still happened during new Al-Mg-Si-Cu alloy hot deformation. Decreasing of Z leads to more adequate proceeding of DRX. The main type of DRX is DDRX(Discontinuous Dynamic Recrystallization). Machanisms of DDRX nucleation appear likely that some subgrains coarse by mergering other adjacent subgains.In addition, GDRX(Geometric Dynamic Recrystallization)also happened during hot deformation4) For T6,the feasible heat treat process parameter of this new Al-Mg-Si-Cu alloy is that: soluted at 550℃/2h,then quenched using water as quenching medium,artificially aged at 185℃/2h+200℃/lh. After heat treated as above parameters, its tensile strength can reach over 340MPa and hardness over 105HB, as well as elongation over 12%, which were associated with the formation of fine and dispersed precipitates, leading to excellent age hardening.For T5, its tensile strength can reach 325MPa and yield strength can reach 275 MPa and hardness over 120HV, as well as elongation over 12%.