预回复工艺对7085铝合金挤压材微观组织与抗腐蚀性能的影响

Effect of pre-recovery-annealing treatment on microstructure and corrosion resistance of extruded 7085 aluminum alloy

采用光学显微镜（OM）、电子背散射衍射检验（EBSD）、晶间腐蚀及剥落腐蚀试验,研究了两种预回复工艺（工艺1：250℃×24 h＋300℃×6 h＋350℃×6 h＋400℃×6 h;工艺2：250℃×24 h＋300℃×6 h＋350℃×6 h＋400℃×6 h＋450℃×6 h）对经强化固溶（470℃×2 h＋480℃×2 h＋490℃×2 h）和T76时效（121℃×5 h＋153℃×16 h）处理后的7085铝合金挤压材微观组织及抗腐蚀性能的影响。结果表明,与未经预回复处理的合金相比,经预回复处理后的合金晶粒显著细化（从61.822μm分别下降到6.135μm与10.892μm）、晶界平均角度显著降低（从26.6°分别降低至14.2°和12.9°）、低角度晶界（1-15°）的数目百分数显著提高（分别从31.3%提高到74.4%与76.1%）、抗晶间腐蚀性能明显改善（最大腐蚀深度由152.8μm分别减少到127.8μm与83.3μm）、抗剥落腐蚀性能也得到显著改善。对比两种预回复工艺,经预回复工艺2处理后合金的晶粒尺寸较经预回复工艺1有所长大,其晶界平均角度较低、低角度晶界的数目百分数也较低,抗腐蚀性能也更好,相对更佳。

Effect of different pre-recovery-annealing treatments on microstructure and corrosion resistance of extruded 7085 aluminum alloy after enhanced-solid-solution and T76 aging treated was investigated by means of optical microscope（ OM）,electron back-scattered diffraction（ EBSD）,intergranular corrosion and exfoliation corrosion tests. The results show that the pre-recovery-annealing treatments can restrain recrystallization,refine grain size,reduce the average angle of grain boundaries,increase proportion of low angle grain boundaries,and improve intergranular and exfoliation corrosion resistance significantly. The pre-recovery-annealing process of 250 ℃ ×24 h ＋ 300 ℃ × 6 h ＋ 350 ℃ × 6 h ＋ 450 ℃ × 6 h is recommended,by which the alloy exhibits larger grain size,lower value of average angle of grain boundaries and higher fraction of low angle grain boundaries; and good corrosion resistance is obtained.