一种Al-Mg-Si合金板材生产过程中的组织演变

Study on microstructure evolution of Al-Mg-Si alloy sheet in production

采用金相显微镜、扫描电子显微镜、X射线衍射仪等分析方法,研究了一种汽车用Al-Mg-Si合金在铸造、均匀化、热轧、退火、冷轧、固溶和预时效工业化生产过程中的组织和织构演变行为。结果表明:铸态合金晶粒近似呈等轴状,热轧后转变为片层状的变形态晶粒,退火过程中发生再结晶,但保留与轧制方向平行的位向关系,冷轧后晶粒再次变为片层状,固溶和预时效之后发生完全再结晶,形成无畸变的等轴晶粒;铸态合金中主要含有β-富铁相、α-富铁相、Mg2Si相和Q相,沿晶界分布,均匀化之后Mg_(2)Si相和Q相回溶,片层较薄的β-富铁相转变为α-富铁相,片层较厚的β-富铁相未发生改变,热轧之后析出相数量增多,与富铁相一样都平行于轧制方向分布,退火后析出相数量进一步增多,尺寸也有所增加,冷轧后析出相趋于细小弥散分布,经过固溶、预时效后,析出相回溶,基体只残留富铁相;在热轧或冷轧过程中,B、S、C织构增强,而退火或固溶+预时效环节由于再结晶的发生,B、S、C织构减弱,Cube和Goss织构增强。

The grain structure,phase structure,and texture evolution behavior of an Al-Mg-Si alloy used in automobiles during industrial production processes such as casting,homogenization,hot rolling,annealing,cold rolling,solid solution,and pre-aging were studied using metallographic microscopy,scanning electron microscopy,X-ray diffraction,and other analysis methods.The results show that the grain size of the cast alloy is approximately equiaxed,and after hot rolling,it transforms into a deformed lamellar shaped grain.During annealing,recrystallization occurs,but the orientation parallel to the rolling direction is retained.After cold rolling,the grains change again into lamellar shaped ones,and after solid solution and pre-aging,complete recrystallization occurs,forming undistorted equiaxed grains.The cast alloy mainly containsβ-iron-rich phase,α-iron-rich phase,Mg,Si phase,and Q phase,distributed along grain boundaries.After homogenization,the Mg,Si phase and Q phase dissolve back,thinnerβ-iron-rich phase is transformed intoα-iron-rich phase,thickerβ-iron-rich phase is not changed.After hot rolling,the number of precipitated pha-ses increases,and they are distributed parallel to the rolling direction the same as the iron-rich phase.After annealing,the number of precipitates further increases and the size also increases.After cold rolling,the precipitates tend to have a fine and dispersed distribution.After solid solution and pre-aging,the precipitated phase dissolves back,and only the iron-rich phase remains in the matrix.During the hot or cold rolling process,the B,S,and C textures are enhanced,while the annealing or solution+pre-aging process weakens the B,S,and C textures and enhances the Cube and Goss textures due to the occurrence of recrystallization.