Cold-rolling method for a wrought mg alloy with weak/non-basal texture and a cold rolled sheet

Abstract

The present invention relates to a cold-rolling method for cold-rolling a wrought Mg alloy with a weak or non-basal texture as well as a cold-rolled sheet, the method comprising the steps of: pre-treating a billet of the wrought Mg alloy with a weak or non-basal texture, and then cold rolling it; wherein the weak or non-basal texture plane of said billet is selected as a rolling plane, and the rolling direction is parallel to the rolling plane; and said billet is cold rolled at room temperature to a sheet or foil with a thickness of 0.1 to 100 mm, wherein single-pass or multi-pass rolling is used, and the cold rolling is followed by an annealing at 200 to 400° C. for 10 min to 48 h.

Description

TECHNICAL FIELD OF THE INVENTION[0001]The present invention relates to a cold-rolling technique for manufacturing a cold rolled Mg sheet with excellent mechanical properties, which is featured to obviously enhance the strength of the wrought Mg alloy with weak / non-basal texture by the large stain cold-rolling.BACKGROUND OF THE INVENTION[0002]Compared with materials, such as plastics, woods, and other metals, magnesium and its alloys are more attractive candidates for a number of structural applications due to their high specific strength and stiffness, excellent damping capacity, good electromagnetic shielding, good machinability, and ease to be recycled. Therefore, they are progressively used in automotive, electronic and consumer electric appliance, leisure and gymnasium apparatus, bicycle, aviation, aerospace and defense industries. They are called “the Green Engineering Materials in the 21st Century”, and it can be expected that the consumption of Mg alloy as metallic structural...

AI Technical Summary

Benefits of technology

[0006]To solve the problems found in the wrought Mg alloys with a weak or non-basal texture in the prior art, such as low strength, poor surface finish quality, the product size overstepping the tolerance, a thin sheet or foil having small thickness being not able to obtained therefrom, non-uniform microstructure and mechanical properties, the single use, and so on, the present invention provides a cold-rolling method for a wrought Mg alloy with a weak or non-basal texture. The strength of the wrought Mg alloy with a weak or non-basal texture can be enhanced by more than 15% by this cold-rolling method, as compared with that the billet of the wrought Mg alloy with a weak or non-basal texture for cold-rolling. Furthermore, the strength of the cold-rolled sheet, processed by proper annealing treatment, is increased by no less than 10%, and the elongation δ along the rolling direction is no less than 25%, compared with the billet of the wrought Mg alloy with a weak or non-basal texture for cold-rolling.

[0017]Compared with the billet of the wrought Mg alloy with a weak or non-basal texture, the strength of the cold-rolled sheet is increased by no less than 15%.

[0020]1) In the invention, a large strain cold rolling is employed to process the wrought Mg alloy with a weak or non-basal texture at room temperature. High density of dislocations and a certain amount of twins can be introduced in the microstructure, and the intensity of basal texture component is increased during the cold-rolling process. Therefore, the yield strength and ultimate tensile strength of said billet are obviously enhanced. The cold rolled sheet has a relatively high strength at room temperature. The method is easy to manipulate and control.

[0022]3) The original billet of the wrought Mg alloy with a weak or non-basal texture is eventually cold rolled to thin sheets or foils with the thickness of 0.1 to 100 mm in the invention. The strength of the cold-rolled sheet can be enhanced by no less than 15% along the rolling direction; then appropriate annealing treatment is adopted to the cold-rolled sheet, so the strength of the annealed cold-rolled sheet can be increased by no less than 10%, while ensuring a relatively high elongation (δ≧25%) along the rolling direction, in comparison with the original billet of the wrought Mg alloy with a weak or non-basal texture. The strength of the cold rolled sheet is increased significantly, or the ultimate product of this invention exhibits high strength, accompanied with excellent ductility.

Problems solved by technology

Thus, Mg alloys has a poor ductility, workability and formability at middle to low temperature and room temperature, which limits their further press formability and industrial applications.

Thereby, the wrought Mg alloy with a weak or non-basal texture presents a low competitive power and its application is severely limited.

Cold-rolling process is mainly employed to produce thin sheets and belts, which can solve the problems that the size of the hot rolled sheet oversteps the tolerance and the mechanical properties in the same sheet are not uniform, due to the heat drop and non-uniform distribution of temperature during hot rolling.

Nevertheless, the cold rolling response of the conventional wrought Mg alloy sheets, such as AZ31 rolled sheet, is generally poor due to its low ductility at room temperature, as shown in FIG. 1 (a), and it is easy to produce cracks in the surface or side margin when a reduction per pass is more than 10% at room temperature, as shown in FIG. 1 (b), thus it is improper for the conventional Mg alloy sheet to be cold rolled in commercial process, that is, a relatively large stain cold-rolling process.

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