| To further improve the mechanical properties of ZM6ing magnesium alloyunder T6state, the magnesium alloy was firstly soluted and then pre-deformedbefore aging on the base of the superior T6heat treatment process. With theintegation of the analysis such as OM, TEM, XRD, SEM, hardness, tensile atroom temperature and so on, the influence of pre-deformation on the ZM6ingmagnesium alloy was studied.By controlling the tensile pre-strain, the influence of the tensile pre-deformation on the microstructure and properties under pre-deformed state andaging state after solution was researched. With the increase of the tensile pre-strain (2%-10%), the number of twins gradually increased and precipitate rob-like second phase mainly containing Zn and Zr in morphology after the solution.Through aging, there is no significant change in the number of twins, onlyfinding small amount of residual dislocations. For the reason that dislocationsprovides a diffusion path for the precipitation of second phase, the distribution ofsecond phase in the matrix is gradually dispersed, and part of the second phasechange from the needle to a curved shape. As the deformation increases, thestrength of the pre-stretched ZM6firstly increases and then flattens and theelongation decreases in the direction of zero degree. While the amount ofdeformation is8%, the tensile strength reaches a maximum value of297MPa.But the deformation reaches10%, the elongation of alloy dropped to4%; In thedirection of90°, the strength and elongation of the alloy gradually increasedwith the increase of deformation. When the deformation reaches10%, the tensilestrength and elongation of the alloy are290MPa and11%, respectively. To pre- deformed ZM6, the tensile specimens fracture in the way of transgranular andintergranular and most of them crack from the coarse Zr precipitates. With theelongation increasing, the proportion of transgranular fracture increases. Thefracture gradually shows ductile-brittle fracture morphology.By controlling the compression pre-strain, the influence of the compressionpre-deformation on the microstructure and properties under pre-deformed stateand aging state after solution was researched. Compared with the tensile pre-deformation, the change principle of the microstructure is almost the same. Butin the same deformation, the number of twins the increase of the tensile pre-strain, the width of twins is larger. As the deformation increases, the strength ofthe pre-stretched ZM6firstly increases and then flattens in the direction of zerodegree. While the amount of deformation is14%, the strength and elongation ofthe alloys are275MPa and14%, respectively. In the direction of90°, thestrength of the alloy firstly increases and then decreases and the elongationgradually decreases with the increase of deformation. When the deformationreaches8%, the strength of the alloy are315MPa. Meanwhile, the deformationreaches14%, the strength of the alloy decreases to4.5%. Compared with thetensile pre-deformed ZM6, the fracture mechanism and rules of specimenschanges little.In summary, compared with T6heat treatment, the pre-deformation heattreatment can significantly improve the mechanical properties of the aged ZM6magnesium alloy at room temperature. The best pre-deformation heat treatmentprocess is:540℃×14h, pre-compressed8%deformation in the direction of90°,200℃×8h. |
