固溶工艺对Al-Zn-Mg-Cu合金组织与性能的影响

Effect of solution process on microstructure and properties of Al-Zn-Mg-Cu alloy

首先对Al-Zn-Mg-Cu合金分别进行了二级固溶处理(450℃×30 min+470℃×60 min)和三级固溶处理(450℃×30 min+470℃×60 min+485℃×30 min),随后对其进行了120℃时效24 h的处理。采用光学显微镜、扫描电镜、X射线衍射仪、透射电镜等研究了不同工艺固溶处理对Al-Zn-Mg-Cu合金微观组织和性能的影响,并对固溶时效态合金的拉伸性能和晶间腐蚀性能进行了测试。结果表明:与二级固溶工艺相比,经过三级固溶工艺处理后,Al-Zn-Mg-Cu合金中高温残留相Al_(2)CuMg得到有效消除,合金时效态样品晶间腐蚀24 h后最大侵蚀深度由250.78μm降至124.22μm,同时合金的拉伸性能得到提升,抗拉强度由601 MPa提升至653 MPa,屈服强度由546 MPa提升至596 MPa,断后伸长率由10.3%提升至14.5%。这主要是由于Al_(2)CuMg残留相在固溶过程中的消除提高了淬火态Cu、Mg溶质原子的过饱和度,增加了晶内析出相的体积分数,即晶内析出相与位错相互作用的剪切强化效果得以提升。同时拉伸过程中可能发生在Al_(2)CuMg粗大相附近的应力集中也被减弱,合金的塑性得到改善。此外,Al_(2)CuMg残留相的消除提高了合金在时效过程中晶界析出相中的Cu含量,提高了其晶间腐蚀性能。

Firstly,Al-Zn-Mg-Cu alloy was subjected to two-stage solution treatment(450℃×30 min+470℃×60 min)and three-stage solution treatment(450℃×30 min+470℃×60 min+485℃×30 min),respectively,followed by a 120℃aging treatment for 24 h.Effect of different solution treatments on microstructure and properties of the Al-Zn-Mg-Cu alloy was studied by means of optical microscope,scanning electron microscopy,X-ray diffraction and transmission electron microscopy.The tensile and intergranular corrosion properties of the solution-aged alloy were also tested.The results show that compared with the two-stage solution process,the hightemperature residual phase Al_(2)CuMg in the Al-Zn-Mg-Cu alloy is effectively eliminated after the three-stage solution treatment.After 24 h of intergranular corrosion,the maximum corrosion depth of the aged alloy decreases from 250.78μm to 124.22μm,and the tensile properties of the alloy are improved,the tensile strength is increased from 601 MPa to 653 MPa,the yield strength is increased from 546 MPa to 596 MPa,and the elongation is increased from 10.3%to 14.5%.This is mainly due to the elimination of residual Al_(2)CuMg phase during the solution treatment,which increases the supersaturation of quenched Cu and Mg solute atoms and increases the volume fraction of intragranular precipitates.This means that the shear strengthening effect of the interaction between intragranular precipitates and dislocations is improved.At the same time,the stress concentration that may occur near the coarse phase of Al_(2)CuMg during the stretching process is also weakened,and the plasticity of the alloy is improved.In addition,the elimination of residual Al_(2)CuMg phases increases the Cu content in the grain boundary precipitates of the alloy during aging,thereby improving its intergranular corrosion performance.