2219大规格铸锭成分偏析行为及多向锻-固溶时效热处理对铸锭组织和性能的影响

Composition segregation behavior of 2219 aluminum alloy ingot with big size and effect of multi-axial forging and solution-aging treatment on microstructure and mechanical properties of ingot

采用超声半连续铸造方法制备了d 1250mm大规格2219铝合金铸锭,并通过光谱仪、OM、SEM、拉伸试验等手段研究了大铸锭成分偏析现象及多向锻-固溶时效热处理对铸锭组织和性能的影响。结果表明,沿铸锭径向方向合金的凝固冷却速度波动较大,导致主合金元素产生严重的宏观偏析,从而促使中心部非平衡结晶相Al2Cu数量较多且枝晶粗大,愈往边部非平衡结晶相数量逐渐减少,枝晶也呈减薄趋势。经多级均匀化和多向锻-固溶时效热处理后,(2/3~5/6)半径处综合性能最优,轴向和径向性能基本一致,强度分别为420 MPa、323 MPa,伸长率为8.7%,切向强度分别为448 MPa、343 MPa,伸长率为11.0%。从边部到中心部,2219合金的拉伸断裂由韧性断裂为主逐渐过渡到以脆性断裂为主。可见,由于凝固速度造成的大铸锭的偏析现象可以通过多向锻-固溶时效热处理手段加以改善。

The composition segregation behavior of 2219 aluminum alloy produced by ultrasonic semi-continuous ingot with diameter of 1250 mm and the effect of multi-axial forging and solution-aging on microstructure and mechanical properties of 2219 aluminum alloy were investigated by spectrograph, optical microscopy, scanning electron microscopy and tensile testing. The results show that the main alloy element along the radial of casting has serious segregation under the volatile cooling rate, which impels non-uniform distribution of non-equilibrium crystallization phase Al2 Cu. The billet core has higher numbers of Al2 Cu phase and dendrites are coarse. The non-equilibrium crystallization phase reduces gradually and the dendrites refines obviously from the core to the edge. After being treated by multi-stage homogenization and multidirectional forging-solution and aging treatment, the area between 2/3 and 5/6 of ingot radius has the best comprehensive mechanical properties with the tensile strength of 420 MPa（axial and radial directions） and 448 MPa（tangent direction）, the yield strength of 323 MPa（axial and radial directions） and 343 MPa（tangent direction）, and the elongation of 8.70%（axial and radial directions） and 11.0%（tangent direction）. The main fracture mechanisms of 2219 alloy will make the transition from ductile fracture to brittle fracture along the radial of casting. Therefore, multidirectional forging-solution and aging treatment is an effective means to weaken the macro-segregation.