预回复退火2099铝锂合金挤压材的组织和位错强化

Microstructure and Dislocation Strengthening of Pre-Recovery-Anneal 2099 Al-Li Alloy Extrusions

2099铝锂合金具有低密度、高比强度、高比刚度以及优良的超塑成型性和耐腐蚀性能等优点,因而被广泛应用于航空航天及武器装备制造领域。本文采用硬度与电导率测试、X射线衍射(XRD)仪显微分析、电子背散射衍射(EBSD)等方法,研究了在固溶处理前进行预回复退火处理对2099铝锂合金挤压材组织和位错强化的影响。实验结果表明:250℃/24 h+300℃/6 h+350℃/6 h+400℃/6 h的预回复退火工艺可以有效地细化合金晶粒(合金晶粒平均尺寸由5.004μm下降到4.775μm),提高合金的硬度和导电率(硬度由HV171.46提高到HV175.13,导电率由16.24%ICAS提高到16.44%ICAS),降低合金内的晶格应变、位错等晶体缺陷(位错密度由0.8284×1014降低到0.4530×1014m-2),同时也降低位错对强度的贡献(位错对强度的贡献由49.705 MPa降低到36.754 MPa)。2099铝合金晶粒细小,合金中小角度晶界比例较高,其再结晶抗力较高,预回复处理对其具有一定的抑制再结晶和强化作用,但不是很明显。

2099 A1-Li alloy has the merits of low density, high specific strength, high specific stiffness, good superplastic formability and decay resistance, so it is widely used in the aerospace and weapon fields. The effect of pre-recovery-anneal treatment before solid solution on the microstructure and dislocation strengthening of Sr microalloyed 2099 A1-Li Alloy was studied by hardness test, conduc- tivity test, X-ray diffraction （XRD） and electron backscattered diffraction （EBSD） analysis. The results showed that pre-recovery an- nealing （250 ℃ ×24 h ＋300 ℃ ×6 h ＋350 ℃ x6 h ＋400 ℃ ×6 h） could refine the grain size which decreased from 5. 004 to 4. 775 μm, the hardness was improved from HV171.46 to HV175.13, and the conductivity was improved from 16.24% ICAS to 16.44% ICAS. Pre-recovery-anneal treatment could reduce the lattice strain and dislocations of the alloy （ the dislocation density reduced from 0. 8284 × 1014 to 0. 4530 ×1014 m -2 ）, and decrease the contribution of dislocation to strength which reduced from 49. 705 to 36. 754 MPa. 2099 A1-Li alloy had very fine grains and high proportion of low angle grain boundaries, so the influence of pre-recovery-anneal treatment on the strength and recrystallization restraining was not that significant.