均匀化热处理对5083铝合金难溶相与晶粒尺寸的影响

Effect of homogenization heat treatment on refractory phase and grain size of 5083 aluminum alloy

为研究5083铝合金均匀化过程中难溶相含量、种类以及晶粒尺寸的变化,采用金相显微镜(OM)、扫描电子显微镜(SEM)、能谱仪(EDS)、差示扫描量热仪(DSC)和X射线衍射仪(XRD)对材料组织进行表征。结果表明:铸态5083铝合金中的难溶相由Al(FeMnCr)相、Al(FeMnCr)Si相和Mg_(2)Si相组成。使用相图计算对铸态组织成分进行验证,结果与实验基本吻合。随着温度从460℃升高至560℃,导电率先升高后降低。这与组织中的弥散相析出和难溶相溶解有关。均匀化制度为540℃/10 h,560℃/10 h时,难溶相主要以针片状Al(FeMnCr)相为主,Mg_(2)Si相回溶充分,面积分数分别为0.730%和0.632%,未出现过烧组织的同时,晶内有明显的弥散相粒子析出。因此均匀化温度只有≥540℃才能实现5083铝合金凝固组织中部分难溶相的回溶。提高均匀化温度和延长均匀化时间均会增加晶粒尺寸,当均匀化温度小于540℃时,难溶相变化对晶粒长大影响不大,当均匀化温度大于540℃时,难溶相回溶的同时平均晶粒直径开始大于140μm。

In order to study the changes in the content,type of the refractory phases and grain size during homogenization of the 5083 aluminum alloy,material microstructure was characterized by metallographic microscope(OM),scanning electron microscope(SEM),energy dispersive spectrometer(EDS),differential scanning calorimetry(DSC)and X-ray diffractometer(XRD).The results show that the refractory phases in the cast 5083 aluminum alloy are composed of Al(FeMnCr)phases,Al(FeMnCr)Si phases and Mg_(2)Si phases.The composition of the cast state alloy was verified by using phase diagram calculations,and the results are basically consistent with the experiment.As the temperature rises from 460℃to 560℃,the electrical conductivity increases firstly and then decreases.This is related to the precipitation of dispersed phase and the dissolution of refractory phase in the structure.When the homogenization processing is 540℃/10 h and 560℃/10 h,the refractory phase is dominated by the needle-flake Al(FeMnCr)phases,Mg_(2)Si phases is fully solubilized,the area fractions are 0.730%and 0.632%,respectively,and there is no over burned tissue at the same time,and there are obvious dispersed phase particles in the grain.Therefore,to dissolve part of the refractory phases in cast 5083 aluminum alloy,the homogenization temperature must be≥540℃.Increasing homogenization temperature and prolonging homogenization time will increase grain size.When the homogenization temperature is less than 540℃,the insoluble phase changes have little effect on the grain growth,when the homogenization temperature is greater than 540℃,the average grain size begins to be greater than 140μm,and the refractory phase is dissolved at the same time.