Effect Of Snake Rolling On Microstructure And Properties Of Mg-Gd-Y-Nd-Zr Alloy

Magnesium alloy has the advantages of low density,high specific strength and high specific stiffness,which has a broad application prospect in the aerospace field.However,due to the close packed hexagonal structure of magnesium,only basal slip and tensile twinning are easy to start at room temperature,so the rolled magnesium alloy sheets usually form a strong basal texture,resulting in poor plasticity,which seriously limits its application fields.It is an important research direction to improve the room temperature plasticity of magnesium alloys by weakening the basal texture or deflecting the basal surface.The results show that the asymmetric deformation technology can introduce shear deformation,which can not only refine the grain,but also weaken the basal texture and improve the mechanical properties.Snake rolling is a new type of asymmetric deformation method proposed in recent years.It has been used to improve the microstructure and mechanical properties of aluminum alloy by introducing shear deformation through dislocation of upper and lower rolls and different speed.However,the research on snake rolling of magnesium alloy is rarely reported.Taking Mg-Gd-Y-Nd-Zr alloy as the research object,the effects of different speed ratio and rolling path on Microstructure and properties of snake rolled Mg-Gd-Y-Nd-Zr alloy sheet were studied.The results are as follows:(1)The effect of different speed ratio on the texture of snake rolled sheet was studied.Due to the shear effect in snake rolling process,the texture components of normal deviation of basal plane from normal direction of plate are formed in snake rolling plate.With the increase of different speed ratio,the angle of normal deviation of basal plane from normal direction of plate first increases and then decreases.When the different speed ratio of upper and lower rolls is 1.4:1,the normal deviation of basal plane from normal direction of plate is obvious The angle of normal direction is the largest,reaching 17 ° which is more conducive to the starting of basal slip.(2)The effect of different speed ratio on the mechanical properties of snake rolled sheet was studied.The tensile strength of conventional rolling sheet is the highest,reaching 308 MPa,and the plasticity is the lowest,which is 2.5%.snake rolling reduces the strength and increases the plasticity of sheet.With the increase of different speed ratio,the room temperature elongation of sheet first increases and then decreases.When the different speed ratio is 1.4:1,the room temperature plasticity of sheet is the best,and the elongation reaches9.6%,which is 287% higher than that of conventional rolling.(3)The mechanism of improving the room temperature plasticity of the sheet by snake rolling is studied.Due to the existence of strong texture components in snake rolled sheet which deviate from the normal direction of the sheet along the rolling direction,the basal slip and prismatic slip of snake rolled samples are initiated during the tensile deformation at room temperature,which improves the room temperature elongation.However,due to the strong basal texture of conventional rolled samples,it is difficult to initiate the basal slip during the tensile deformation at room temperature,which leads to the failure of the alloy.The plasticity is low at room temperature.(4)The effect of rolling path on the microstructure and texture of the alloy was studied.The results show that the samples rotated 180° in rolling direction,transverse direction and normal direction(RD-180°,TD-180° and ND-180° respectively)are mainly composed of deformed grains with high dislocation density,while the samples rotated 90° in normal direction(ND-90 ° respectively)are mainly composed of fine recrystallized grains with low dislocation density;the basal normal direction of the strongest texture components in RD-180° and TD-180° samples deviates from the normal direction of the plate The angle of the strongest texture component in ND-180° and ND-90° samples deviates more from the normal direction of the plate.(5)The effect of rolling path on the mechanical properties of the alloy was studied.The tensile strength of TD-180° sample is the highest,318 MPa,and the elongation after fracture is the lowest,2.0%;The ND-90° sample has the lowest tensile strength of 287 MPa and the highest elongation after fracture of 10.0%.The high plasticity of the sample is mainly attributed to the deviation of the basal normal direction from the plate normal direction of the strongest texture component,fine grain size and low dislocation density.The ND-180° sample has good comprehensive properties,with tensile strength of 307 MPa and elongation after fracture of 9.5%,respectively For the strongest texture component,the normal direction of the basal plane deviates from the normal direction of the plate and the dislocation density is relatively low.