CN116356185A - A method for promoting the plastic forming of high-difficult-formable magnesium alloys - Google Patents

Abstract

A plastic processing forming method for promoting magnesium alloy which is difficult to form belongs to the field of plastic material processing. Aiming at the problem of poor rolling forming capability of Mg-RE (containing Gd, dy, er, ho and other heavy rare earth elements) alloy with high rare earth content. The rolling forming capability of the Mg-RE alloy is improved mainly through the synergistic effect of a pre-heat-force coupling technology and a small amount of Sn, single-pass deformation of the Mg-RE alloy with large reduction can be realized, the single-pass reduction can reach 25-60%, the surface quality of the obtained Mg-RE alloy plate is good, no crack and no cracking exist, and the production efficiency and the product quality of the Mg-RE alloy plate are improved.

Description

A method for promoting the plastic forming of high-difficult-formable magnesium alloys

technical field

The invention belongs to the field of plastic material processing, in particular to a method for promoting the plastic processing of high-difficulty-forming magnesium alloys.

Background technique

After entering the modern society, the consumption of fossil energy and iron and steel resources has accelerated, the problem of energy depletion has become more and more serious, and the crisis of human survival has emerged. Energy conservation and emission reduction have become the focus of attention at home and abroad. Magnesium alloy is the lightest engineering metal material, which has important application value in the fields of automobile, track, aviation, national defense and military industry. my country is a country with large magnesium resources and a strong country in the development and application of magnesium alloys. Vigorously exerting the advantages of magnesium resources in my country and continuously applying the developed magnesium alloy products and technologies to my country's industrial fields will help the upgrading of my country's industrial equipment.

However, pure magnesium and most magnesium alloys have a hexagonal close-packed structure (HCP), and the lattice c/a=1.6236 at room temperature is very close to the ideal c/a=1.633, which has only 2 independent groups at room temperature. The surface slip system leads to poor plastic deformation ability, especially in the rolling process, which often manifests as difficult rolling, surface microcracks and serious edge cracks, which seriously restricts the development and application of magnesium alloy sheets.

As an important magnesium alloy product, Mg-RE alloy has always been the focus of domestic and foreign scholars. The existing Mg-RE alloys mainly focus on Mg-Gd, Mg-Y and other alloy systems, which have good room temperature and High-temperature mechanical properties, its products are mainly extrusion-based. At present, ultra-high magnesium alloys with a strength of more than 500 MPa are mainly concentrated in Mg-Gd alloys, mainly because the Gd element has a high equilibrium solid solubility at high temperature, but the equilibrium solid solubility is seriously reduced at low temperature, so Mg -Gd alloys, especially alloys with a Gd content above 10wt.%, have a very significant aging strengthening effect. After deformation, aging and other treatments, Mg-Gd alloys tend to have a higher strengthening effect. Currently, the room temperature strength is known The highest magnesium alloy is Mg-Gd series alloy, its strength can reach more than 700MPa.

Therefore, Mg-RE alloy has always been an important magnesium alloy product concerned by domestic scholars. After nearly two decades of development, although many Mg-RE alloy products with excellent performance have been successfully developed, there has always been the problem that they cannot be rolled and formed quickly. Therefore, there are very few rolled products of Mg-RE alloys at present. In order to obtain high-quality Mg-RE alloy sheets, it must be achieved through a cumbersome rolling process. The main feature is high temperature and multi-pass rolling. The rolling temperature is generally higher than 450 °C, and the deformation in a single pass is Between 5-10%, the rolling passes generally range from 10-30 passes according to product requirements, which leads to extremely low production efficiency and low product quality of Mg-RE alloy plates. Therefore, how to improve the production efficiency of magnesium alloy sheets with high rare earth content and improve the quality of their products has become the key to whether the magnesium alloy sheets with high rare earth content can be widely used.

The invention relates to a method for improving the rolling forming ability of a magnesium alloy with high rare earth content. The single-pass rolling forming ability of Mg-RE alloy can be significantly improved by adding a small amount of Sn and corresponding pre-"thermal-mechanical" coupling technology. Finally, the Mg-RE alloy sheet with good surface quality, no cracks and no cracks can be obtained through single-pass large reduction deformation, which significantly improves the production efficiency of the alloy sheet and saves costs.

Contents of the invention

The problem to be solved by the present invention is how to improve the rolling forming ability of magnesium alloys with high rare earth content. It mainly adopts the addition of a small amount of Sn and cooperates with effective pre-"heat-force" coupling technology to realize high rare earth content under certain rolling process conditions. Efficient preparation of Mg-RE alloy sheets with high content. As a result, Mg-RE alloy plate products with good surface quality are obtained, which has a unique effect in improving the quality and production efficiency of plate products.

The invention provides an improved rolling forming method of magnesium alloy with high rare earth content, specifically the preparation of Mg-RE alloy plate with high rare earth content, wherein the alloy composition of the plate is that Sn is added as an auxiliary element in Mg-RE alloy, Mg - The total amount of RE in the RE alloy is ≥13wt.%, and is selected from heavy rare earth elements such as Gd, Dy, Er, Ho, etc.; the Sn element does not participate in phase formation, and its content is 0.4wt.%-1.0wt.%.

Its main steps are as follows:

(1) Add a small amount of Sn to the magnesium alloy with high rare earth content, the main melting process is as follows:

First, the surface of the prepared Mg-RE alloy is cleaned to remove impurities such as scale, and then divided into small pieces, and placed in a resistance melting furnace with a temperature of 720-800°C for heat preservation. After the alloy is melted, stir evenly. After standing still for 10-25 minutes, raise the furnace temperature to 720-800°C again, keep it warm for 5-10 minutes, turn off the power supply of the heating furnace, and set the furnace temperature to 650-720°C. After the temperature is stable, add 0.4-1.0wt. % Sn is added into the alloy liquid, vigorously stirred, and kept at 650-720° C. for 10-25 minutes, and then the alloy is poured into an ordinary low-carbon steel mold.

(2) The prepared Mg-Gd alloy containing a small amount of Sn element is solution treated, the solution treatment temperature is 450-550 ℃, and after 5-25 hours of heat preservation, the coarse eutectic phase in the alloy disappears, thus obtaining super Saturated magnesium alloy solid solution, and then use the pre-"thermal-mechanical" coupling technology to carry out extrusion thinning pretreatment on the supersaturated magnesium alloy solid solution. The treatment conditions are 360-400°C, the holding time is 10-15min, and the deformation is 5%-10%. , and finally water quenched. Subsequently, the pretreated product is subjected to rolling treatment. The rolling process is as follows: the temperature is 400-450° C., and the holding time is 5-15 minutes, which is higher than the pre-"thermal-mechanical" coupling treatment temperature. Finally, a high-quality Mg-RE alloy sheet is obtained, with a single-pass reduction of 25-60% and a sheet thickness of 2-4mm. , The thickness of the sheet is 2-4mm. The surface quality of the final Mg-RE alloy plate of the present invention is good, without cracks and cracks, and the production efficiency is high.

Substantive features and remarkable progress of the present invention

1. The present invention involves adding a small amount of Sn to improve the roll-formability of Mg-RE alloys. This element only improves the roll-formability and does not participate in phase formation.

2. The rapid preparation of Mg-RE alloy plates is realized by using the pre-"thermal-mechanical" coupling technology and the synergistic technology of Sn elements.

3. The rolling process involved in the present invention is simple and practical, and high-quality Mg-RE alloy sheet products can be obtained without multi-pass cumulative deformation.

4. The present invention has obvious advantages in technological progress, not only saving the production cost of Mg-RE alloy plates, but also significantly improving the production efficiency of Mg-RE alloys.

Specific embodiments (please reflect the effect advantage of the present invention for embodiment supplementary characterization)

The present invention will be further described below in conjunction with the examples, but the present invention is not limited to the following examples.

Example 1

Clean the surface of the prepared Mg-13wt.% RE alloy, remove the scale, cut it into small pieces, place it in a resistance furnace with a temperature of 780 ° C, melt and stir it, then let it stand for 15 minutes, and raise the temperature of the furnace to 780°C, keep warm for 20 minutes, turn off the power of the furnace, and set the temperature of the furnace to 700°C. After the temperature is stable, add 0.5wt.% Sn into the alloy liquid, stir vigorously, and keep it at 700°C for 10 minutes , and finally cast Mg-RE alloy containing a small amount of Sn. Then extrude at 360°C, with a deformation of 5%, and keep warm for 10 minutes. The pretreated plate was kept at 400°C for 5 minutes, water quenched, and rolled. The deformation was 25%, and a Mg-RE plate with a good surface quality and a thickness of 4mm was obtained. The yield strength at room temperature could reach 320MPa and the elongation was 8%.

Example 2

Clean the surface of the prepared Mg-20wt.% RE alloy, remove the scale, cut it into small pieces, place it in a resistance furnace with a temperature of 780 ° C, melt and stir it, then let it stand for 15 minutes, and raise the temperature of the furnace to 780°C, keep warm for 20 minutes, turn off the power of the furnace, and set the temperature of the furnace to 700°C, after the temperature is stable, add 1.0wt.% Sn into the alloy liquid, stir vigorously, and keep it at 700°C for 10 minutes , and finally cast Mg-RE alloy containing a small amount of Sn. Then extrude at 400°C with a deformation of 10% and keep warm for 15 minutes. The pretreated sheet was kept at 450°C for 15 minutes, water quenched, and rolled. The deformation was 60%, and a Mg-RE sheet with a good surface quality and a thickness of 2mm was obtained. The yield strength at room temperature could reach 450MPa and the elongation was 15%.

Example 3

Clean the surface of the prepared Mg-16wt.% RE alloy, remove the scale, cut it into small pieces, place it in a resistance furnace with a temperature of 780 ° C, melt and stir it, then let it stand for 15 minutes, and raise the temperature of the furnace to 780°C, keep warm for 20 minutes, turn off the power of the furnace, and set the temperature of the furnace to 700°C, after the temperature is stable, add 0.6wt.% Sn into the alloy liquid, stir vigorously, and keep it at 700°C for 10 minutes , and finally cast Mg-RE alloy containing a small amount of Sn. Then extrude at 380°C with a deformation of 6%, hold for 8 minutes, and quench in water. The pretreated sheet was kept at 425°C for 10 minutes, and then rolled, with a deformation of 40%, to obtain a Mg-RE sheet with a good surface quality and a thickness of 3mm. The yield strength at room temperature can reach 395MPa, and the elongation is 11%.

Example 4

The surface of the prepared Mg-18wt.% RE alloy was cleaned, the scale was removed, and it was cut into small pieces, placed in a resistance furnace with a temperature of 780°C, melted and stirred, then left to stand for 15 minutes, and the temperature of the furnace was raised to 780°C, keep warm for 20 minutes, turn off the power of the furnace, and set the temperature of the furnace to 700°C, after the temperature is stable, add 1.0wt.% Sn into the alloy liquid, stir vigorously, and keep it at 700°C for 10 minutes , and finally cast Mg-RE alloy containing a small amount of Sn. Then extrude at 395°C with a deformation of 5%, keep it warm for 10 minutes, and quench in water. The pretreated sheet was kept at 435°C for 10 minutes, and then rolled, with a deformation of 25%, to obtain a Mg-RE sheet with a good surface quality and a thickness of 4mm. The yield strength at room temperature can reach 387MPa, and the elongation is 6%.

Claims (4)

1. A method for promoting plastic forming of high-difficult-formable magnesium alloys, characterized in that, it is specifically the preparation of Mg-RE alloy plates with high rare earth content, wherein the alloy composition of the plates is that Sn is added as auxiliary elements in Mg-RE alloys, Mg - The total amount of RE in the RE alloy is ≥13wt.%, and is selected from heavy rare earth elements such as Gd, Dy, Er, Ho, etc.; the Sn element does not participate in phase formation, and its content is 0.4wt.%-1.0wt.%. 2. according to claim 1, a kind of method for promoting the plastic working of high-difficult-formable magnesium alloys is characterized in that, its main steps are as follows: (1) Add a small amount of Sn to the magnesium alloy with high rare earth content, the main melting process is as follows: First, the surface of the prepared Mg-RE alloy is cleaned to remove impurities such as scale, and then divided into small pieces, and placed in a resistance melting furnace with a temperature of 720-800°C for heat preservation. After the alloy is melted, stir evenly. After standing still for 10-25 minutes, raise the furnace temperature to 720-800°C again, keep it warm for 5-10 minutes, turn off the power supply of the heating furnace, and set the furnace temperature to 650-720°C. After the temperature is stable, add 0.4-1.0wt. Add % Sn into the alloy liquid, stir vigorously, and keep it at 650-720°C for 10-25 minutes, then pour the alloy into an ordinary low-carbon steel mold; (2) The prepared Mg-Gd alloy containing a small amount of Sn element is solution treated, the solution treatment temperature is 450-550 ℃, and after 5-25 hours of heat preservation, the coarse eutectic phase in the alloy disappears, thus obtaining super Saturated magnesium alloy solid solution, and then use the pre-"thermal-mechanical" coupling technology to carry out extrusion thinning pretreatment on the supersaturated magnesium alloy solid solution. The treatment conditions are 360-400°C, the holding time is 10-15min, and the deformation is 5%-10%. , and finally water quenched. Subsequently, the pretreated product is subjected to rolling treatment. The rolling process is as follows: the temperature is 400-450° C., and the holding time is 5-15 minutes, which is higher than the pre-"thermal-mechanical" coupling treatment temperature. 3. The method according to claim 2, characterized in that the pressing amount in a single pass can reach 25-60%, and the plate thickness is 2-4mm. 4. The magnesium alloy plate prepared by the method according to any one of claims 1-3.