CN113046663B - Preparation method of 'double-layer sandwich' rolled high-strength rare earth magnesium alloy - Google Patents

Abstract

A preparation method of a 'double-layer sandwich' rolled high-strength rare earth magnesium alloy belongs to the technical field of magnesium alloys. The rare earth magnesium alloy comprises, by mass, 10.0-15.0% of Gd, 0-2.0% of Er, 0-1.0% of Zr, the sum of the Gd, the Er and the Zr is not less than 10.0% and not more than 15.0%, and the balance of Mg. A rolling process of 'double-layer sandwich'. The rolling deformation temperature range is 300-500 ℃. The alloy and the rolling technology thereof involved in the invention are different from the prior magnesium alloy and plate preparation technology thereof, and the high-strength rare earth magnesium alloy plate with smooth surface, thin thickness and no crack can be obtained.

Description

A kind of preparation method of "double sandwich" rolling high-strength rare earth magnesium alloy

technical field

The invention relates to a "double-sandwich" rolling high-strength rare-earth magnesium alloy preparation technology, in particular to the preparation of the high-strength rare-earth magnesium alloy sheet through a certain alloy composition, a smelting process and a subsequent rolling process, belonging to the technical field of magnesium alloys.

Background technique

With the rapid development of science and technology, people's requirements for low-carbon and low-energy-consumption materials in modern industrial production are increasingly demanding, and magnesium alloys, as the lightest metal structural materials, have attracted widespread attention. Among them, magnesium alloy sheet is a product with high technology content and high added value. The application of magnesium alloy sheets in industrial production can greatly simplify the process of deep processing of magnesium alloys, thereby reducing production costs and expanding its application range. Depending on the shape and size of magnesium alloy sheets, they can be used in aerospace, aviation, automotive, electronics and other industries. Therefore, the development of magnesium alloy sheet forming technology has become an important direction in the development of the magnesium industry. However, the absolute mechanical properties of magnesium alloys are very low, and room temperature deformation is difficult, which severely limits the industrial production and application of magnesium alloy sheets.

Most magnesium alloys have a hexagonal close-packed structure, which has a series of different slip regimes compared to the cubic structure, namely <a> dislocation slip at the basal and prismatic planes and <c+a at the conical planes >Dislocation slip. There are significant differences in the critical shear stress required to activate different slip systems. At room temperature, the critical shear stress for activating basal plane dislocation slip is much lower than the critical shear stress for activating non-basal plane dislocation slip on prismatic and conical planes. Therefore, the basal plane slip is dominant when the magnesium alloy is deformed at room temperature. However, basal plane slip can only provide two independent slip systems, which is far less than the requirement of at least five independent slip systems required for uniform plastic deformation of crystals, and therefore, the plastic formability of magnesium alloys is poor. As the amount of deformation increases, the base plane slip gradually tends to a hard orientation, and the deformation can only be coordinated in the form of twinning. The twinning modes existing in magnesium alloys mainly include {10-12}<-1011> tensile twinning and {10-11}<-1012> compression twinning. Among all twinning modes, the tensile twinning {10-12}<-1011> has the smallest critical shear stress. Tensile twinning and basal plane slip occurred mainly during the deformation process of magnesium alloys. Due to its very limited deformation mode, magnesium alloys formed a strong texture during machining. The difference in critical shear stress for cylindrical and conical slip is reduced, but strong texture formation is still observed in rolled and extruded magnesium alloys. In addition, these strong textures persisted during subsequent heat treatment, and the texture strength increased with grain growth. The texture responds to mechanical loading, further reducing the plastic formability of magnesium alloys. Therefore, the texture control of wrought magnesium alloys has an important influence on improving its plastic forming ability.

Relevant studies have shown that the addition of rare earth elements to magnesium alloys can effectively improve the plastic forming ability of the alloy and improve the mechanical properties of the alloy at room temperature and high temperature. Therefore, in recent decades, the development and application of rare earth magnesium alloys have attracted much attention. The addition of rare earth elements to magnesium alloys can change the main deformation and dynamic recrystallization mechanism to obtain wrought magnesium alloy products with lower texture strength. A notable feature of texture weakening in wrought magnesium alloys is the generation of some special texture components, namely "rare earth texture". The common "rare earth texture" is the <11-21> crystallographic orientation parallel to the extrusion direction formed during extrusion and an atypical TD-direction-expanding texture formed during rolling. The presence of "rare earth texture" helps to improve the formability of magnesium alloys at room temperature and reduce mechanical anisotropy.

Among the Mg-RE alloys currently studied, the Mg-Gd alloys have good comprehensive mechanical properties. The common strengthening methods in Mg-Gd alloys include grain refinement strengthening, solid solution strengthening and second phase strengthening. Grain refinement strengthening: The grain boundary can effectively hinder the transmission of slip, and cause stress concentration in front of the grain boundary, forcing more slip systems to open, thereby making the alloy deformation more uniform. Therefore, grain refinement strengthening is the only way to increase both strength and toughness. Mg-Gd alloys mainly refine the grains through the following two ways. One is that Gd element acts as a modifier to increase the nucleation rate of the alloy, thereby refining the grain structure, and the other is to make the alloy occur through plastic deformation. Recrystallization to refine the grain structure; solid solution strengthening: due to the difference in size and elastic modulus of Gd atoms and Mg atoms, when Gd atoms are dissolved in the Mg lattice, the surrounding crystals will be elastically distorted, resulting in The stress field interacts with the dislocation stress field to strengthen the crystal; precipitation strengthening: Mg-Gd alloys have a good aging strengthening effect. When the temperature is high, the rare earth element Gd and the maximum solid solubility reach 23.49wt.% and the solid solubility decreases significantly with the decrease of temperature. When the temperature is 200 °C, the Gd solid solubility is about 3.82wt.% (0.61at.% ), so Gd has a good precipitation strengthening effect. The research shows that the precipitation sequence of Mg-Gd binary alloy is: SSSS supersaturated solid solution→β″(D019)→β′(cbco)→β ₁ (FCC)→β(FCC). The β′ metastable phase has a convex lens shape. The metastable phase in the shape of a convex lens is perpendicular to the basal plane (0002), which can effectively hinder the slippage of matrix dislocations, so it has a high strengthening effect and is also the main strengthening phase when the alloy is aged.

Considering the material design, the smaller the content of the coarse second phase in the alloy, the better the processing of the magnesium metal sheet, otherwise it will lead to the cracking of the alloy during the rolling process. However, the smaller the content of the second phase, the worse the strengthening effect of the second phase, resulting in low alloy performance. Therefore, choosing an appropriate amount of rare earth elements is the key to developing a high-strength rollable rare earth-magnesium alloy. Moreover, the rolling temperature range of Mg-RE series alloys is small and difficult to control, so it is very important to explore the rolling conditions for obtaining Mg-RE series magnesium alloys.

The invention relates to a "double-sandwich" rolling high-strength rare-earth magnesium alloy preparation technology. The composition and mass percentage of the rare earth magnesium alloy are 10.0-15.0wt.% Gd, 0-2.0wt.% Er, 0-1.0wt% Zr, the sum of the mass percentages of Gd, Er and Zr elements is not less than 10.0% and Not higher than 15.0%, and the remainder is Mg. Combining with a specific preparation process, it is described in this application as a new type of rolling process, the main feature of which is a "double-sandwich" rolling process. The rolling deformation temperature range is 300 to 500 °C. The alloy and its rolling technology involved in the present invention are different from the previous magnesium alloy and its sheet preparation technology, and can obtain a high-strength rare-earth magnesium alloy sheet with smooth surface, thin thickness and no cracks.

SUMMARY OF THE INVENTION

The invention relates to a new alloy and a preparation method of the alloy plate, and provides a magnesium alloy material that can be rolled into a plate and a novel "double-sandwich" rolling process. The Mg-Gd-Er-Zr alloy in the invention is a high-strength rare-earth magnesium alloy plate that can be rolled and formed. It overcomes the shortcomings of low absolute strength and poor plasticity of the current magnesium alloy, and is a magnesium alloy sheet material with application prospects.

alloy composition:

In order to obtain the Mg-RE series alloy with higher absolute strength and better plastic forming ability, the present invention adopts the following preparation method: Gd, Er and Zr are selected as the main alloying elements, and their addition amounts are 10.0-15.0wt. %Gd, 0-2.0wt.%Er, 0-1.0Zr, the sum of the total mass percentage of rare earth elements Gd, Er and Zr is not less than 10.0% and not higher than 15.0%, and the rest is Mg.

The preparation process includes the following steps:

(1) The casting alloy is obtained by ordinary melting process, and the prepared casting alloy is heat treated at a temperature of 480-530 °C, a holding time of 2-10 h, and quenched in water at 25 °C; then cutting is performed to obtain an extruded blank , and place the extruded blank in a holding furnace for heat treatment, the temperature of the holding furnace is 300-450 ° C, the holding time is 1h, and then extruded, the extrusion rate is 0.5-2mm/s, and the thickness of the extrusion is 4-12mm. Pressing the sheet, cutting the extruded sheet to obtain a rolled blank;

(2) Carry out "double-sandwich" rolling, and wrap a layer of thermal insulation material on both surfaces of the rolled blank. The thermal insulation material is copper, aluminum, steel and other sheet products. It is 1-0.01:1, the function of this method is to keep warm and promote deformation; the process flow of this method is: before rolling, first roll the blank and thermal insulation material in the order of thermal insulation material, rolling blank and thermal insulation material Combined into a sandwich structure, and then fix the sandwich structure with copper wire/or iron wire, and then put it into the heating furnace for heating and heat preservation. , immediately put it into cold water for quenching, and finally separate the separator and sample of this pass, and so on, in the whole rolling process, each pass is done in this way; the temperature range of "double-sandwich" rolling is 300-500 ℃, the holding time of each pass is 5min-20min, the reduction amount of each pass is 5-30%, the cumulative reduction is 60-80%, the thickness of the final plate is 0.5-3.0mm, the surface and edge are smooth, No cracking.

Substantive features and significant progress of the present invention:

1. Invented a high-strength rare-earth magnesium alloy material that can be rolled and formed, the total deformation can reach 60-80%, and its rolling forming ability is better than the current common Mg-RE alloys.

2. The present invention adopts a novel preparation process, which is characterized by a segmented preparation process combining extrusion and rolling.

3. The present invention adopts a new type of rolling technology, which is called "double-sandwich" rolling, which is characterized in that the sample is wrapped with two layers of thermal insulation material and then subjected to subsequent heat treatment and rolling process.

4. In addition to the "double-sandwich" rolling, the rolling technology in the present invention also adopts a wider temperature range, the temperature range is 300-500°C, and the deformation amount per pass is 5-30%.

5. The alloy has strong rolling forming ability, and high-strength rare-earth magnesium alloy sheet with smooth surface can be obtained without special equipment.

Detailed ways

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

The Mg-10Gd-1Er-0.5Zr alloy obtained by ordinary casting is subjected to heat treatment at a temperature of 480 ° C and a holding time of 10 h, and is quenched in 25 ° C water, and then subjected to cutting to obtain an extruded blank, which is extruded. The blank is placed in a holding furnace for heat treatment, and the temperature of the holding furnace is 300°C. The extrusion rate was set to 1.0 mm/s, and an extruded sheet with a thickness of 5 mm was obtained. The obtained extruded sheet is subjected to cutting processing to obtain a rolled blank. The rolled blank is wrapped with two layers of thermal insulation material to obtain a "double sandwich" structure. The "double-sandwich" structure was placed in a holding furnace for heat treatment, the temperature of the holding furnace was 300°C, and the rolling rate was set to 4.0 m/s. First, the rolling temperature is 300°C, holding for 10 minutes, the deformation of each pass is 10%, the rolling direction is along the extrusion direction, and rolling is performed for 1 pass; then the same rolling temperature is maintained, and the sample is at this temperature. Heat preservation for 15 minutes, the deformation amount per pass is 15%, the rolling direction is along the extrusion direction, and rolling is performed for 4 passes; the rolling temperature is set to 300 ° C, the holding time is 20 minutes, and the deformation amount per pass is 5%. The rolling direction is along the extrusion direction, and the rolling is carried out in 2 passes. A plate with a thickness of about 1.0 mm was obtained, and the accumulated deformation was about 80%. Sandwich rolling technology is used in each pass. Finally, a magnesium alloy sheet with excellent mechanical properties is obtained, and its mechanical properties are: tensile strength: 400Mpa; yield strength: 260Mpa; elongation: 10%.

Example 2

The Mg-11Gd-1Er-0.5Zr alloy obtained by ordinary casting is heat treated at a temperature of 510 ° C, the holding time is 8 h, and quenched in 25 ° C water, and then cut to obtain an extruded blank, which is extruded. The blank is placed in a holding furnace for heat treatment, and the temperature of the holding furnace is 410°C. The extrusion rate was set to 1.0 mm/s, and an extruded sheet with a thickness of 8 mm was obtained. The obtained extruded sheet is subjected to cutting processing to obtain a rolled blank. The rolled blank is wrapped with two layers of thermal insulation material to obtain a "double sandwich" structure. The "double-sandwich" structure was placed in a holding furnace for heat treatment, the temperature of the holding furnace was 380°C, and the rolling speed was set to 2.0 m/s. First, the rolling temperature is 380°C, the deformation of each pass is 20%, the rolling direction is along the extrusion direction, and one pass is rolled; then the same rolling temperature of 380°C is maintained, and the sample is kept at this temperature. 15min, the deformation amount per pass is 15%, the rolling direction is along the extrusion direction, and rolling is performed for 8 passes; then the holding time is extended for 20min, the rolling temperature is set to 380 °C, and the deformation amount per pass is 10%, The rolling direction is along the extrusion direction, and 5 passes are rolled. A plate with a thickness of about 2 mm was obtained, and the accumulated deformation was about 75%. Sandwich rolling technology is used in each pass. Finally, a magnesium alloy sheet with excellent mechanical properties is obtained, and its mechanical properties are: tensile strength: 460Mpa; yield strength: 320Mpa; elongation: 8.0%.

Example 3

The Mg-12Gd-1Er-0.5Zr alloy obtained by ordinary casting is heat-treated at a temperature of 520 ° C and a holding time of 6 h, and then quenched in 25 ° C water, and then subjected to cutting to obtain an extruded blank, which is extruded. The blank is placed in a holding furnace for heat treatment, and the temperature of the holding furnace is 450°C. The extrusion rate was set to 1.0 mm/s, and an extruded sheet with a thickness of 10 mm was obtained. The obtained extruded sheet is subjected to cutting processing to obtain a rolled blank. The rolled blank is wrapped with two layers of thermal insulation material to obtain a "double sandwich" structure. The "double sandwich" structure was placed in a holding furnace for heat treatment, the temperature of the holding furnace was 450°C, and the rolling speed was set to 2.0 m/s. First, the rolling temperature is 450°C, the deformation of each pass is 20%, the rolling direction is along the extrusion direction, and one pass is rolled; then the same rolling temperature of 450°C is maintained, and the sample is kept at this temperature. 15min, the deformation amount per pass is 15%, the rolling direction is along the extrusion direction, and the rolling is 8 passes; then the holding time is reduced to 10min, the deformation amount per pass is 10%, and the rolling direction is along the extrusion direction. , 5 passes of rolling. A plate with a thickness of about 2 mm was obtained, and the accumulated deformation was about 80%. Sandwich rolling technology is used in each pass. Finally, a magnesium alloy sheet with excellent mechanical properties is obtained, and its mechanical properties are: tensile strength: 485Mpa; yield strength: 460Mpa; elongation: 5%.

Example 4

The Mg-13Gd-1Er-0.5Zr alloy obtained by ordinary casting is heat treated at a temperature of 520°C and a holding time of 10h, and quenched in 25°C water, and then cut to obtain an extruded blank, which is extruded. The blank is placed in a holding furnace for heat treatment, and the temperature of the holding furnace is 430°C. The extrusion rate was set to 1.0 mm/s, and an extruded sheet with a thickness of 5 mm was obtained. The obtained extruded sheet is subjected to cutting processing to obtain a rolled blank. The rolled blank is wrapped with two layers of thermal insulation material to obtain a "double sandwich" structure. The "double sandwich" structure was placed in a holding furnace for heat treatment, the temperature of the holding furnace was 480°C, and the rolling speed was set to 2.0 m/s. First, the rolling temperature is 480°C, the deformation of each pass is 20%, the rolling direction is along the extrusion direction, and one pass is rolled; then the same rolling temperature of 480°C is maintained, and the sample is kept at this temperature. 15min, the deformation of each pass is 15%, the rolling direction is along the extrusion direction, and the rolling is 8 passes; then the holding time is 12min, the deformation amount of each pass is 10%, and the rolling direction is along the extrusion direction, 5 passes of rolling. A plate with a thickness of about 1.0 mm was obtained, and the accumulated deformation was about 80%. Sandwich rolling technology is used in each pass. Finally, a magnesium alloy sheet with excellent mechanical properties is obtained, and its mechanical properties are: tensile strength: 550Mpa; yield strength: 463Mpa; elongation: 3%.

Example 5

The Mg-14Gd-1Er-0.5Zr alloy obtained by ordinary casting is heat-treated at a temperature of 530 ° C and a holding time of 2 h, and quenched in 25 ° C water, and then cut to obtain an extruded blank, which is extruded. The blank is placed in a holding furnace for heat treatment, and the temperature of the holding furnace is 450°C. The extrusion rate was set to 1.0 mm/s, and an extruded sheet with a thickness of 5 mm was obtained. The obtained extruded sheet is subjected to cutting processing to obtain a rolled blank. The rolled blank is wrapped with two layers of thermal insulation material to obtain a "double sandwich" structure. The "double-sandwich" structure was placed in a holding furnace for heat treatment, the temperature of the holding furnace was 500°C, and the rolling speed was set to 2.0 m/s. First, the rolling temperature was 500 °C, the deformation amount per pass was 20%, the rolling direction was along the extrusion direction, and one pass was rolled; The deformation amount of each pass is 15%, the rolling direction is along the extrusion direction, and the rolling is carried out for 8 passes; then the same rolling temperature is maintained, the holding time is 11 minutes, the deformation amount per pass is 10%, and the rolling direction is along the According to the extrusion direction, rolling is carried out for 5 passes. A plate with a thickness of about 1.0 mm was obtained, and the accumulated deformation was about 80%. Sandwich rolling technology is used in each pass. Finally, a magnesium alloy sheet with excellent mechanical properties is obtained, and its mechanical properties are: tensile strength: 548Mpa; yield strength: 442Mpa; elongation: 2%.

Claims (2)

1. a preparation method of " double-layer sandwich " rolling high-strength rare earth magnesium alloy, is characterized in that, comprises the following steps: (1) The casting alloy is obtained by ordinary melting process, and the prepared casting alloy is heat treated at a temperature of 480-530 °C, a holding time of 2-10 h, and quenched in water at 25 °C; then cutting is performed to obtain an extruded blank , and place the extruded blank in a holding furnace for heat treatment, the temperature of the holding furnace is 300-450 ° C, the holding time is 1h, and then extruded, the extrusion rate is 0.5-2mm/s, and the thickness of the extrusion is 4-12mm. Pressing the sheet, cutting the extruded sheet to obtain a rolled blank; (2) Carry out "double-sandwich" rolling, and wrap a layer of thermal insulation material on both surfaces of the rolled blank. The thermal insulation material is copper, aluminum, and steel sheet products. 1-0.01:1; The process flow is: before rolling, firstly, the rolling blank and thermal insulation material are combined into a sandwich structure in the order of thermal insulation material, rolling blank and thermal insulation material, and then the sandwich structure is formed by copper wire/or iron wire. Fix, and then put it into the heating furnace for heating and heat preservation, and the sandwich product can be put into the rolling inlet after the holding time. , sample separation, and so on, in the whole rolling process, each pass is done in this way; the temperature range of "double-sandwich" rolling is 300-500 ℃, and the holding time of each pass is 5min-20min. The secondary reduction is 5-30%, the cumulative reduction is 60-80%, and the thickness of the final plate is 0.5-3.0mm, the surface and edge are smooth, and there is no cracking; Alloy composition: Gd, Er, Zr are selected as the main alloying elements, and their addition amounts are 10.0-15.0wt. The sum of the total mass percentage is not lower than 10.0% and not higher than 15.0%, and the rest is Mg. 2. The high-strength rare-earth magnesium alloy prepared according to the method of claim 1.