Microstructure And Mechanical Property Of The Pre-aged 6201 Aluminum Alloy Processed By R-Conform Process

As a heat treatable aluminum alloy,Al-Mg-Si alloy has excellent comprehensive properties such as high strength,good formability and electrical conductivity,which has been widely used in automotive,overhead lines and other fields.In this paper,the repetitive continuous extrusion forming process?R-Conform process?drawing and subsequent artificial aging treatment were carried out on the pre-aged 6201 Al alloy produced by continuous casting and rolling.The microstructure characteristic and mechanical property evolution of the aluminum alloy were investigated using electron back-scatter diffraction?EBSD?,transmission electron microscopy?TEM?,X-ray diffractometer,polarizing metallographic microscopy,and tensile testing.The effect of pre-aging treatment on the evolution of microstructure and properties of Al-Mg-Si alloy during the process of R-Conform,drawing and artificial aging was investigated.The main results and are as follows that:1)In two different pre-aging conditions,the tensile strength and ductility of the Al-Mg-Si alloy increase first and then decrease generally,the production of strength-and ductility of alloy increases gradually and reaches the peak in the fourth and fifth Conform pass respectively,and that it tends to be stable with the increase of Conform pass.2)In two different pre-aging conditions,the grain size of the alloy decreases continuously from 259?m to 60?m and the grain is more equiaxed and uniform,the density of dislocation density of in the alloy increases continuously from 10¹³ to 10¹⁴m^-2,and the dispersive Mg₂Si phase is gradually dissolved into the matrix with the increase of the Conform pass.3)There is an obvious hardening phenomenon during artificial aging treatment.The hardness of the alloy increases first and then decreases,and the hardening curve has a peak value with the increase of aging time.The strength and elongation of the alloy increase gradually with the increase of R-Conform pass,and the comprehensive mechanical properties of the alloy is enhanced obviously after the artificial aging.4)The fracture morphology of aluminum alloy after artificial aging is mainly composed of dimple.The fracture microstructure of original continuous rolling and casting alloys has mixed-rupture characteristics of quasi-cleavage and dimples.With the increase of the extrusion pass,there are many larger dimples on the dimple fracture surface after the fourth draw pass fracture and the dimples are smaller,more uniform,and the elongation is higher in the seventh pass.5)The grain of the aluminum alloy after drawing is fibrous along the drawing axis.The dislocation increases greatly and it appears a large number of subgrains formed in the grain.The dispersive distribution and fine?"phases are precipitated in the alloy and gradually increase with the increase of the extrusion path after artificial aging,this is the main reason for the high strength and plasticity of the aluminum-alloy after the seventh pass alloy.