Al-10．78Zn-2．78Mg-2．59Cu-0．22Zr-0．047Sr铝合金挤压材的性能

Microstructure and Mechanical Properties of an Extruded Al-Alloy Al-10.78Zn-2.78Mg-2.59Cu-0.22Zr-0.047Sr

研究了Al-10.78Zn-2.78Mg-2.59Cu-0.22Zr-0.047Sr铝合金挤压材在固溶-T652和预回复-固溶-T652时的组织和性能。结果表明:该合金在121℃×24h时效制度下,预回复退火处理可有效细化晶粒(从9.76μm减小到5.56μm),降低晶界平均角度(从23.59°降低至17.41°),显著提高低角度晶界百分比(从53%提高到67%),提高位错强化,并显著抑制再结晶的发生;与固溶-T652相比,预回复-固溶-T652工艺在不降低强度的情况下可提高其晶间和剥落腐蚀性能(最大晶间腐蚀深度从125.0μm减少到91.4μm,剥落腐蚀从EB级提高到EA级);在预回复-固溶-T652状态下合金的抗拉强度达到728MPa,预回复退火处理能提高合金的强度。位错强化和低角度晶界强化是合金的主要强化机制。

Effect of solid solution-T652 treatment and pre-recovery-solid solution-T652 treatment on microstructure and mechanical properties of an extruded AI- alloy AI- 10.78Zn- 2.78Mg- 2.59Cu- 0.22Zr- 0.047Sr was studied. The results show that after a pre-recovery-annealing treatment and then a post-ag- ing at 121℃ for 24 h the grain size of the extrusion can be refined from 9.76 μm to 5.56 μm; the average grain boundary angle can be reduced from 23.59° to 17.41°, i.e.the percentage of low angle grain bound- ary is significantly enhanced from 53% to 67%, therewith, the dislocation strengthening is increased, and the recrystallization process may be suppressed. Compared with solid solution-T652, the pre-recovery- annealing treatment can enhance the corrosion resistance of the alloy, i.e. the maximum corrosion depth may be reduced from 125.0 μm to 91.4μm, thus its exfoliation corrosion rating increased from EB to EA grade, while the alloy maintained a high strength. The strength of the alloy after the pre-recovery-solid so- lution plus T652 treatment is up to 728 MPa. Dislocation strengthening and low angle grain boundary strengthening are the main strengthening mechanisms.