KR20170133510A - Moldable magnesium-based alloys for processing - Google Patents

Abstract

0.1 to 2.0 Zn; Ca of 0.05 to 1.5; Zr of 0.1 to 1.0; A rare earth element of 0 to 1.3 or a mixture thereof containing Gd or Y; 0 to 0.3 Sr, 0 to 0.7 Al; (% By weight) essentially consisting of magnesium and inevitable impurities of the remainder.

Description

Moldable magnesium-based alloys for processing

The present invention generally relates to a new magnesium-calcium alloy composition. More particularly, the present invention relates to a magnesium-zinc-rare earth-calcium-zirconium and magnesium-calcium-zinc (zirconium) -based alloy for processing, which comprises a plurality of alloying elements, A magnesium alloy working sheet, and a magnesium alloy working sheet.

The following description of the background of the present invention is intended to assist in understanding the present invention. It is to be understood, however, that the description is not intended to be " obvious "

Magnesium (Mg) is the lightest structural material with a density of 1.74 g / cm ³ at 20 ° C, which is about two thirds of the aluminum (Al) density and one quarter of the steel density. This property makes the magnesium a promising candidate for replacing steel and Al alloys. In particular, interest in the development of structural magnesium sheet alloys in the automotive, aerospace, light rail, and high-speed train industries is rapidly increasing. This is because a wide range of applications of magnesium alloys can save energy and reduce running costs. However, conventional Mg-sheet alloys, AZ31 and ZK60, have not been widely used in the industry due to poor ductility and moldability at moderate temperatures.

Conventional magnesium machining / sheet alloys such as AZ31 and ZK60 form strong basal texture during thermomechanical processing and have strong anisotropic mechanical properties. Thus, these alloys exhibit lower moldability than metallic competitors such as aluminum and steel alloys at moderate temperatures. Due to the limited moldability of conventional magnesium commercial alloys at moderate temperatures, broad application of such materials is limited.

The formability of the alloy sheet can be improved by changing the alloy composition and controlling the processing parameters. Mg-RE (rare earth) alloy sheets show substantial improvements in ductility and formability compared to commercial AZ31 alloy sheets. In addition, according to recently reported documents, the addition of non-RE element, i.e. Zn, to Mg-RE alloys can provide ductility and formability superior to soft and moldable Mg-RE binary alloy sheets. Nevertheless, there is no report yet on how to make magnesium alloy sheets superior in ductility and moldability than Mg-Zn-Gd alloy sheets.

Therefore, it would be desirable to develop a novel magnesium alloy containing Ca, preferably an Mg-based processing alloy for sheet formation with good formability and mechanical properties.

A first embodiment of the present invention is a Zn-Zn-doped Zn-doped Zn-doped Zn- Ca of 0.05 to 1.5; Zr of 0.1 to 1.0; A rare earth element of 0 to 1.3 or a mixture thereof containing Gd or Y; 0 to 0.3 Sr, Al: 0 to 0.7; (% By weight) essentially consisting of magnesium and unavoidable impurities of the remainder.

The present invention relates to a first aspect of a magnesium-zinc-rare earth-calcium-zirconium and magnesium-calcium-zinc (zirconium) -based alloy for processing, comprising a plurality of alloying elements for improving moldability. The alloy comprises a lean alloy composition wherein the total amount of alloying elements is preferably less than 4 weight percent (or less). While not wishing to be bound by any theory, the present inventors have found that a lean alloy composition comprising an additive of a low cost alloying element Ca in Mg-Zn-RE-Zr and Mg-Zn- (Zr) alloys significantly reduces the nature of the alloy , And the moldability can be improved. The formability of the resulting Mg-Zn-RE-Ca-Zr alloy with a suitable composition is superior to that of conventional Mg-Zn-Gd- (Zr) alloys.

Depending on the alloy composition, the amount of rare earth element may be present. In the most common form, the magnesium alloy (wt%) comprises 0 to 1.3 rare earth elements or mixtures thereof, but in some embodiments the rare earth elements or mixtures thereof may comprise between 0.05 wt% and 1.3 wt%. The rare earth element or a mixture thereof may contain a lanthanide rare earth element or yttrium. For the purposes of this specification, the lanthanide series elements include element groups having atomic numbers from 57 (lanthanum) to 71 (lutetium). These elements are called lanthanes because the lighter elements in the series are chemically similar to lanthanum. Strictly speaking, lanthanum is a Group 3 element, and its ion La ³⁺ does not have f electrons. However, for the purposes of this specification, it should be understood that lanthanum is included as one of the lanthanide-based rare earth elements. For purposes of the present invention, yttrium will also be considered to be encompassed by the term "rare earth element ". Therefore, the rare earth elements of the lanthanide series include lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. In some embodiments, the rare earth component comprises gadolinium (Gd). In another embodiment, the rare earth component comprises a mixture of gadolinium (Gd) and lanthanum (La). In another embodiment, the rare earth component comprises a mixture of gadolinium and yttrium. In another embodiment, the rare earth component comprises a mixture of rare earth elements of gadolinium or yttrium and lanthanum series. The advantage of embodiments comprising the lanthanide series of rare earth elements or yttrium is their relatively high solubility in magnesium.

It should be understood that the alloying element acts as follows: a rare earth element is added to make the essence thin, and as a result, the moldability of the Mg-Zn alloy is improved at an appropriate temperature. Zirconium is added as a grain refiner. Aluminum is added to promote the age hardening reaction of Mg-Ca-Zn- (Zr) based alloys.

A second aspect of the present invention is a Zn-Zn-based alloy comprising: Zn: 0.1 to 2.0; Ca: 0.05 to 1.5; Zr: 0.1 to 1.0; Gd: 0 to 1.0, preferably 0.05 to 1.0; Sr: 0 to 0.3; La: 0 to 0.3; Al: 0 to 0.7; And the balance of Mg and other inevitable impurities, wherein the total weight percent of the alloying elements is less than 4%.

In a preferred embodiment, the magnesium-based processing alloy comprises Ca: 0.3 to 1.0; Zn: 0.3 to 1.0; Zr: 0.2 to 0.7; Gd: 0.1 to 0.5; Sr: 0 to 0.2; La: 0 to 0.2; Al: 0 to 0.5; And Mg of the remainder and other inevitable impurities, wherein the total weight percentage of the alloying elements is less than 4%.

In some embodiments, the present invention can be distinguished into two general calcium-containing magnesium alloy compositions that contain several alloying elements to improve the moldability of their alloy compositions. The general alloying groups are as follows:

Group 1: Mg-Zn-Gd-Ca-Zr alloy; And

Group 2: Mg-Ca-Zn- (Zr) -based alloy.

The specific alloy composition of each of these groups will now be described:

Group 1: Mg-Zn-Gd-Ca-Zr alloy.

In Group 1, the Mg alloy contains more than 0.5% but less than 2.0% Zn, 0.05-1.0% Gd, 0.05-1.0% Ca, 0.1-1.0% Zr, 0-0 0.3% (Sr), 0% to 0.3% lanthanum (La), 0% to 0.7% Al and the balance Mg, and inevitable other impurities. In addition, the content of Zn preferably ranges from 0.5% to 1.5%. In addition, the content of Gd is preferably more than 0.1% and less than 0.5%. In addition, it is preferable that it contains Ca in excess of 0.1% and less than 0.7%. In addition, the content of Zr is preferably more than 0.2% and less than 0.7%. In addition, the content of Sr is preferably less than 0.2%. In addition, the content of La is preferably less than 0.2%. In addition, the content of Al is preferably more than 0.2% and less than 0.5%.

Group 2: Mg-Ca-Zn- (Zr) -based alloy.

In Group 2, the Mg alloy contains more than 0.3%, less than 1.5% Ca, 0.1-0.8% Zn, 0-1.0%, preferably 0.1-1.0% Gd, 0-0 0.7% Al , 0% to 0.3% Sr, 0.1% to 1.0% Zr, and the balance Mg, and other inevitable impurities. In addition, the content of Ca is preferably in the range of 0.6% to 1.0%. In addition, the content of Zn is preferably more than 0.3% and less than 0.5%. In addition, the content of Gd is preferably more than 0.1% and less than 0.5%. In addition, the content of Al is preferably more than 0.1% and less than 0.7%, more preferably, the content of Al is more than 0.2% and less than 0.5%. In addition, the content of Sr is preferably less than 0.2%. In addition, the content of Zr is preferably more than 0.2% and less than 0.7%.

The total weight of the alloying elements is preferably less than 4%, more preferably less than 3%, and even more preferably less than 2.5%. It should be appreciated that the addition of additional alloys can lead to the formation of secondary phase particles that can act as nucleation sites for cracks during deformation, which may be detrimental to the formability of the Mg-working alloys.

Mg-1Zn-0.4Gd-0.2Ca-0.5Zr, Mg-1Zn-0.4Gd-0.5Ca-0.5Zr, Mg-1Zn-0.4 Mg-0.8Ca-0.1Sr-0.5Zr, Mg-1Zn-0.4Gd-0.2Ca-0.1La-0.5Zr, Mg-0.8Ca-0.4Zn, Mg- 0.8Ca-0.4Zn-0.4Gd, Mg- 0.8Ca -0.4Zn-0.3Al, Mg-0.8Ca-0.4Zn-0.3Al-0.1Sr, Mg-0.8Ca-0.4Zn-0.5Zr, Mg- 0.8Ca-0.4Zn- 0.1Sr- 0.5Zr, Mg- 0.8Ca -0.4Zn-0.4Gd-0.5Zr, or Mg-0.8Ca-0.4Zn-0.1Sr-0.4Gd-0.5Zr.

In a preferred embodiment, the magnesium-based working alloy is selected from one of Mg-1Zn-0.4Gd-0.2Ca-0.5Zr or Mg-0.8Ca-0.4Zn-0.1Sr-0.4Gd-0.5Zr.

Manganese (Mn) is also free of Zr and added to all of the alloys containing Zr, thereby minimizing the iron content and further improving the corrosion resistance. If present, the Mn content is preferably greater than 0.05%, less than 0.7%, more preferably greater than 0.1% and less than 0.5%.

The magnesium-based alloy preferably contains a minimal amount of ancillary impurities. In some embodiments, the magnesium-based alloy comprises less than 0.5% by weight, more preferably less than 0.2% by weight of incidental impurities. The additional impurities may be selected from the group consisting of Li, Be, Ca, Sr, Ba, Sc, Ti, Hf, Mn, Fe, Cu, Ag, Ni, Cd, Al, Si, Ge, Sn, As shown in FIG.

The present invention also relates to a magnesium alloy processing alloy sheet comprising at least one magnesium-based processing alloy according to the first or second aspect of the present invention. In this connection, the inventors do not know to apply Mg-Ca-Zn- (Zr) based alloys in sheet form in the reported documents or patent publications. Therefore, the present inventors think that the sheet form of the magnesium-based processing alloy is unique.

The present invention also relates to a method of producing a magnesium-based alloy sheet product. Therefore, a third aspect of the present invention provides a method of manufacturing a magnesium-based alloy sheet product, the method comprising:

Providing a magnesium alloy melt from the magnesium-based alloy;

Casting the magnesium alloy melt into a slab or strip having a predetermined thickness;

Homogenizing or preheating the cast slab or strip;

Continuously hot-rolling the homogenized or preheated slab or strip at an appropriate temperature to reduce the thickness of the homogenized slab or strip to produce an alloy sheet product of a predetermined thickness; And

Annealing the alloy sheet product at an appropriate temperature for a period of time;

The magnesium alloy melt can be produced using any suitable method. In many embodiments, each element is mixed and melted at a temperature above the liquidus temperature of the alloy embodiment in a suitable vessel, such as a mild steel crucible, in a melting furnace, for example a high frequency induction melting furnace, In an embodiment, the melt is heated to about 760 DEG C in an argon atmosphere.

The casting step may comprise any suitable casting process. For example, the casting step may include casting an ingot or a billet. In other embodiments, the casting step may include casting into a sheet or strip. In some embodiments, the casting step comprises injecting the magnesium alloy melt into one of a direct chill (DC) castor, a sand caster, or a permanent mold caster. For example, the casting step may use a DC cast billet that is subsequently extruded to form a slab or strip after pre-heating. In another embodiment, the casting step comprises feeding the magnesium alloy melt between rolls of a twin-roll castor to produce a strip.

The step of homogenizing or preheating the cast slab or strip preferably takes place at a temperature between 300 and 500 ° C. The actual homogenization temperature depends on the alloy composition. In some embodiments, the homogenizing or pre-heating step of the cast slab or strip is followed by subsequent quenching, preferably water quenching. The homogenizing or pre-heating step of the cast slab or strip is preferably carried out for a period of about 0 to 24 hours.

The homogenized slab or strip is preferably machined into a 5 mm thick strip and then hot rolled. The hot rolling is preferably carried out at a temperature range of 300 to 550 캜, more preferably 350 to 500 캜. Hot rolling typically results in a total thickness reduction of 50 to 95%, preferably 70 to 80%. In some embodiments, hot rolling is performed using multiple rolling passes, and each rolling After passing, the sheet is reheated at a temperature in the range of 350 to 500 占 폚 before the subsequent rolling. The sheet is preferably reheated for about 5 to 20 minutes, preferably for 5 to 10 minutes. The reduction in thickness per pass is preferably about 20%. Thus, if the thickness reduction per pass is about 20%, the total reduction rate can be about 80%.

After final rolling, the sheet was annealed to remove the accumulated strain through stactic recrystallization. The annealing temperature is preferably +/- 50 DEG C from the inflection point of the annealing curve obtained for the composition of the alloy for a 1 hour standard period. In addition, the time for annealing the alloy sheet product is preferably about 1 minute to 24 hours.

The present inventors have found that it is possible to strengthen magnesium-calcium-zinc (zirconium) based alloys of various embodiments of the present invention by artificial aging treatment. Thus, in some embodiments, the method may further comprise applying an age-hardening treatment to the annealed alloy comprising heating the alloy for at least one hour at 150 < 0 > C. The age hardening period depends on a necessary or sufficient period to obtain maximum precipitation hardening.

The invention will now be described with reference to the accompanying drawings, which illustrate certain preferred embodiments of the invention:
BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a flow chart illustrating a method for manufacturing magnesium alloys according to the present invention including an experimental test system.
Figure 2 provides tensile stress-strain curves for annealed B1, B2, B3, B4, and B5 alloy sheets and comparative annealed AZ31 and T4-6016 Al alloy sheets.
Figure 3 provides the tensile stress-strain curves of the annealed B6, B7, B8, B9, B10, B11, B12, and B13 alloy sheets and the comparative annealed AZ31 and T4-6016 Al alloy sheets.
Fig. 4 provides a plot of the age hardening reaction of a Mg-Ca-Zn- (Zr) based alloy sheet.
Figure 5 provides a plot of the hardness variation of the B2 alloy sheet as a function of annealing time at temperatures of 350, 400, 450 and 500 < 0 > C.

The present invention relates to magnesium-zinc-rare earth-calcium-zirconium and magnesium-calcium-zinc (zirconium) alloys for processing which contain a plurality of alloying elements for improving moldability. The present invention improves the formability of magnesium-zinc-rare earth-calcium-zirconium and magnesium-calcium-zinc-zirconium alloys such as Mg-Zn-Gd-Zr alloys by adding a small amount of Ca or Ca- .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a flow chart showing a method for producing a magnesium alloy sheet of the present invention. As shown in FIG. 1, magnesium-zinc-rare earth-calcium-zirconium and magnesium-calcium-zinc- (zirconium) based alloys according to the compositions described herein are first provided in step 105 first.

After the melt preparation, each alloy is cast at 110 using the appropriate casting technique. In some embodiments, the step of casting may include casting an ingot, billet, bar, block, or other molded body. In other embodiments, casting may include casting into the casting step sms sheet or strip.

Specific examples of casting techniques include sand casting with or without a chill plate on two sides of twin roll casting (TRC), casting or DC casting. It should be appreciated that a number of direct-cast (DC) casting methods and apparatus suitable for magnesium alloys are well known in the art and can be used in the process / method of the present invention. The strip or slab may also be made from a DC cast billet with a slab or strip that is then extruded again using a suitable apparatus and method for magnesium alloys known in the art.

In one embodiment, the alloy was melted and cast using a high frequency induction melting furnace using a mild steel crucible at about 760 ° C in an argon atmosphere. The resulting melt was cast into an appropriately sized ingot having a length of 30 mm thickness x 55 mm width x 120 mm.

Homogenization or preheating is used to reduce interdendritic segregation and composition differences associated with the casting process. A suitable commercial practice is to select a temperature of typically 5 to 10 DEG C below a non-equilibrium solidus. Considering that magnesium, zinc and calcium are the main components in the alloy, a temperature range of 300 to 500 DEG C is given depending on the alloy composition. The time required in the homogenization step is determined by the size of the cast ingot, billet, strip or slab. For TRC strips, 2 to 4 hours will be sufficient, but for sand cast slabs or direct cooled cast slabs, up to 24 hours will be required. After the homogenization treatment, a quenching step, typically a water quenching step, is followed.

For experimental purposes, the homogenized ingots are machined into 5 mm thick strips. However, it should be understood that the strip in the casting step can be formed using any number of other techniques as described above.

The homogenized ingot, strip or slab is hot rolled at an appropriate temperature in step 120. Different rolling steps may be used depending on the cast material. For alloy slabs having a thickness of more than 25 mm produced by sand casting, DC casting or any other type of casting, a brake-down rolling step may be used. The purpose of this step is to refine and remove the cast structure as well as to reduce the thickness. The temperature for this step depends on the furnace available in the rolling facility, but usually a temperature between 350 and 500 ° C is used. For alloy strips produced by TRC, the rolling is carried out at a temperature between 250 ° C and 450 ° C without the need for a brake-down rolling step. Hot rolling involves passing the strip between rollers several times. After each rolling pass, the sheet is reheated at a temperature in the range of 350 to 500 占 폚 for about 5 to 10 minutes to raise the temperature before the next pass prior to the next pass. A small number of cold passes with a reduction rate of 10% per pass can also be used for final rolling or sizing operations. The process continues at step 125 until the final thickness (within the set tolerance) is reached. The total reduction rate may be about 85%, and the thickness reduction per pass may be about 20%.

After final rolling, the sheet was annealed at the appropriate temperature and time, and the accumulated deformation was removed through static recrystallization at step 130. The annealing step is a heat treatment process designed to restore the ductility of the strongly strain hardened alloy by rolling. Annealing heat treatment has three steps - recovery, recrystallization and grain growth. During recovery, the physical properties of the alloy, such as electrical conductivity, are restored, while the cold-treated tissue during recrystallization is replaced by a new set of unmodified particles. Recrystallization can be perceived by metal-meal inspection methods and can be confirmed by decreasing hardness or strength and increasing ductility. If the new amorphous particles are heated at a temperature higher than the temperature required for recrystallization and the strength is significantly reduced, grain growth will occur and this should be avoided. The recrystallization temperature depends in particular on the alloy composition, initial particle size and amount prior to deformation; Therefore, this is not a fixed temperature. In practice, this can be specified as the temperature at which a highly strain-hardened (cold worked) alloy is fully recrystallized within one hour.

The optimal annealing temperature for each alloy and condition is determined by measuring the hardness after exposing the alloy at different temperatures for one hour and then determining the annealing curve to determine the approximate temperature at which the recrystallization is terminated and grain growth begins. curve. This temperature can also be identified by the inflection point of the hardness-annealing temperature curve. Using this technique, the optimum temperature can be obtained easily and fairly accurately.

Thereafter, the annealed strip was quenched in a suitable medium, such as water.

Example

A series of experiments were conducted to test the relative merits of the embodiments of the alloys described above and to establish the low temperature moldability of the alloys made to form the sheet product.

A number of alloy compositions comprising alloys developed according to the present invention (B1 to B13) and comparative samples (AZ31 and T4-Al 6016) were formed and tested in these experiments. Table 1 summarizes the composition of each alloy composition tested.

The composition of each tested alloy designation Composition (Nominal composition, wt.%) B1 Mg-1Zn-0.4Gd-0.5Zr B2 Mg-1Zn-0.4Gd-0.2Ca-0.5Zr B3 Mg-1Zn-0.4Gd-0.5Ca-0.5Zr B4 Mg-1Zn-0.4Gd-0.2Ca-0.1Sr-0.5Zr B5 Mg-1Zn-0.4Gd-0.2Ca-0.1La-0.5Zr B6 Mg-0.8Ca-0.4Zn B7 Mg-0.8Ca-0.4Zn-0.4Gd B8 Mg-0.8Ca-0.4Zn-0.3Al B9 Mg-0.8Ca-0.4Zn-0.3Al-0.1Sr B10 Mg-0.8Ca-0.4Zn-0.5Zr B11 Mg-0.8Ca-0.4Zn-0.1Sr-0.5Zr B12 Mg-0.8Ca-0.4Zn-0.4Gd-0.5Zr B13 Mg-0.8Ca-0.4Zn-0.1Sr-0.4Gd-0.5Zr AZ31 Mg-3Al-1Zn-0.3Mn T4-Al 6016 Al-1.3Si-0.25Fe-0.11Mn-0.4Mg

A sheet of each alloy composition was prepared using the method described above. In the experiment, each component was mixed and melted in a high frequency induction furnace using a mild steel crucible in an argon atmosphere at about 760 ° C. The homogenization treatment was performed in a temperature range of 300 to 500 占 폚 according to the alloy composition. After the homogenization treatment, the water quenching step is continued. The homogenized ingot was machined into strips 5 mm thick and then hot rolled in a temperature range of 350-500 ° C. The total thickness reduction was about 80% and the thickness reduction per pass was about 20%. After each rolling pass, the sheet was reheated at a temperature in the range of 350 to 500 DEG C for about 10 minutes before subsequent rolling. After final rolling, the sheet was subjected to an annealing treatment, and the deformation accumulated through the static recrystallization was removed.

These sheets were subjected to mechanical tests, as described in the following examples:

Example 1: Mechanical properties at room temperature

The tensile properties and formability of the above-described as-annealed sheets of the alloys (B1 to B16) and the control groups (AZ31 and T4-Al 6016) were evaluated at room temperature.

An annealed sheet of each studied alloy composition (see Table 1) was tested at room temperature using a screw-driven Instron 4505 machine at a strain rate of 10 < ^-3 > / s along the rolling direction Respectively. The thickness of each tensile sample was about 1 mm and the gage length was about 10 mm. The sample was further rolled to a thickness of 0.5 mm to evaluate the room temperature moldability of the alloy developed in a mini deep drawing test with a 6 mm diameter punch. The diameters of the annealed disks were 9, 9.5, 10, 10.5, 11.5, 13.1 and 14.6 mm. The critical drawing ratio (LDR) is defined as the ratio of the maximum disc diameter that can be plotted against the punch diameter without a complete failure. In conclusion, high LDR values show good moldability and low LDR values show poor moldability.

Table 2 summarizes the mechanical properties of the alloy sheets (B1 to B13) and comparative alloys (AZ31 and Al 6016) formed at room temperature. The tensile stress-strain curves obtained as a result of the annealed Mg-Zn-Gd-Ca-Zr system including the comparison or benchmark of B1, B2, B3, B4 and B5 alloy sheets and AZ31 and Al 6016 alloy sheets 2.

The Mg-Zn-Gd-Ca-Zr alloy sheet exhibited significantly higher ductility than the ductility of the AZ31 alloy sheet. The overall elongation and LDR values of the B1 alloy sheet reached about 32% and 1.93, respectively. The addition of 0.2% Ca to the B1 alloy can further increase the total elongation from 32% to 38%, increase the strength from 141 MPa to 152 MPa, and increase the LDR value from 1.93 to 2.02 It turned out. It is worth noting that the formability, ductility and strength of the B2 alloy sheet are much better than the moldability, ductility and strength of the 6016 alloy sheet. When the Ca content was increased from 0.2% to 0.5% (B3 alloy), the ductility of the B3 alloy sheet was reduced to 33% and the LDR was reduced to 1.87. As a result, Ca indicates that Mg-Zn-Gd-Ca-Zr alloy is essential for improving the formability and strength of the Mg-Zn-Gd-Ca-Zr alloy. However, strict control of the Ca content is necessary. Likewise, addition of 1% Sr or 0.1% La to the B2 alloy increases the strength but may reduce ductility and formability.

Previously, Mg-Ca based alloys were regarded as fragile and thus were not considered candidates suitable for sheet manufacture. However, in the study of the present invention, the addition of dilute Zn (0.4%) to the Mg-0.8Ca alloy can greatly improve not only the formability but also the rolling property and ductility, and the Mg-0.8Ca-0.4Zn alloy sheet Making it ideal for applications.

In this embodiment, an alloy sheet formed of eight different Mg-0.8Ca-0.4Zn based alloys (B6 to B13) was examined. The mechanical properties of B6 to B13 are provided in Table 2. From a comprehensive viewpoint, B13 (Mg-0.8Ca-0.4Zn-0.1Sr-0.4Gd-0.5Zr) has not only yield strength (137 MPa) among all Mg-Ca-Zn- (Zr) The best mechanical properties were also exhibited.

The mechanical test results indicate that Mg-Zn-Gd-Ca-Zr and Mg-Ca-Zn- (Zr) based alloy sheets have higher ductility and moldability than AZ31 alloy sheets. In particular, the ductility, formability and strength of the Mg-Zn-Gd-Ca-Zr alloy sheet can yield higher results than the Al 6016 alloy, and these alloys can be made ideal for a wide range of commercial applications.

Summary of Mechanical Properties of Annealed Samples of Alloy Sheets of the Invention. Annealed AZ31 and T4 treated 6016 Al alloy sheets are provided as benchmarks. designation Yield strength (MPa) UTS (MPa) UE (%) TE (%) SHE LDR B1 141 213 15 32 0.19 1.93 B2 152 224 20 38 0.22 2.02 B3 155 225 21 33 0.23 1.87 B4 161 230 19 36 0.21 1.90 B5 160 229 18 26 0.22 1.78 B6 128 207 13 26 0.20 1.73 B7 125 202 16 25 0.20 1.78 B8 123 206 17 20 0.22 1.72 B9 128 207 16 27 0.21 1.70 B10 137 209 15 26 0.19 1.74 B11 132 206 17 21 0.21 1.79 B12 129 209 17 23 0.21 1.73 B13 137 215 18 23 0.21 1.83 AZ31 119 230 20 23 0.27 1.60 T4-6016 Al 153 254 20 29 0.20 1.90

Note: The best alloy composition is highlighted in bold

Example 2 :

The annealed Mg-Ca-Zn- (Zr) based alloy sheet was subjected to age hardening treatment by heating at 150 DEG C in silicone oil for a sufficient period of time to obtain maximum precipitation hardening.

The aging reaction was measured by Vickers hardness and tensile tests. The tensile properties and formability of the age hardened sheet were measured at room temperature.

The aging curve of the Mg-Ca-Zn- (Zr) alloy sheet subjected to the aging treatment at 150 ° C. after the solution treatment (400 ° C. for 0.5 hour) is shown in FIG.

It has been found that the Mg-Ca-Zn- (Zr) based alloy sheet not only has excellent ductility and moldability, but also has age-hardening reaction characteristics. That is, after sheet production, the strength of these alloy sheets can be further improved by aging at 150 ° C. As shown in Fig. 3 and Table 3, the hardness value of the B6 alloy sheet before aging was 46 VHN. However, after aging treatment at 150 캜 for 30 hours, the B6 alloy sheet reached maximum aging with a hardness increase of 12 VHN to 58 VHN. On the other hand, when 0.4% Gd was added to B6 alloy, the time to reach maximum aging was extended to 72 hours, but when 0.3% Al was added to B6 alloy, it was shortened to 12 hours. The lean addition of Gd or Al to the B6 alloy only changed the time to reach maximum aging, but the maximum hardness value remained the same. In addition, when adding 0.5% Zr or 0.1% Sr to the B6 alloy, the maximum hardness and required time during the heat treatment will not be apparently changed.

A summary of the tensile properties of the Mg-Ca-Zn- (Zr) based alloy sheets under maximum aging conditions is provided in Table 4. The T6 treatment (artificial aging after the heat treatment of the solid solution) reduced the B6 alloy sheet from 128 MPa to 153 MPa, the B7 alloy sheet from 125 MPa to 146 MPa, the B8 alloy sheet from 123 MPa to 163 MPa, the B9 alloy sheet to 128 MPa To 164 MPa, B10 alloy sheet from 137 MPa to 166 MPa, B11 alloy sheet from 132 MPa to 174 MPa, B12 alloy sheet from 129 MPa to 166 MPa, and B13 alloy sheet from 137 MPa to 168 MPa Respectively. The UE, TE and SHE of the Mg-Ca-Zn- (Zr) -based alloy sheet were reduced as expected. In this connection, the ductility was slightly reduced to obtain a B13 alloy sheet, for example, the ductility of the B13 alloy sheet decreased from 23% (annealed) to 19% (maximum age).

The initial hardness, the maximum hardness, the increase in hardness due to precipitation hardening, and the time to reach the maximum hardness of the Mg-Ca-Zn- (Zr) designation Initial hardness (VHN) Maximum Hardness (VHN) Time to reach maximum hardness (hours) B6-T6 46 58 30 B7-T6 46 57 72 B8-T6 47 56 12 B9-T6 47 55 12 B10-T6 46 56 30 B11-T6 47 58 30 B12-T6 47 57 30 B13-T6 48 58 30

Tensile Properties of Mg-Ca-Zn- (Zr) Based Alloy Sheet in Maximum-Age designation Yield strength (MPa) UTS (MPa) UE (%) TE (%) SHE B6-T6 153 232 13 18 0.16 B7-T6 146 228 14 20 0.17 B8-T6 163 234 13 19 0.16 B9-T6 164 233 13 19 0.16 B10-T6 166 235 13 18 0.16 B11-T6 174 241 11 17 0.15 B12-T6 166 234 14 20 0.18 B13-T6 168 236 13 19 0.16

Example 3

The above results show that the B2 alloy sheet shows the most ductility and moldability among the Mg-Zn-Gd-Ca-Zr system. Therefore, in order to further improve the mechanical properties of the alloy sheet, two important processing parameters are defined, namely rolling temperature and annealing conditions.

The B2 alloy sheet was subjected to various hot rolling and annealing conditions to determine thermodynamic process parameters to optimize mechanical properties using the methods and experimental equipment described above. Tables 5 and 6 summarize the tensile properties of the annealed sheets of the two alloys produced under different thermomechanical processing conditions.

During the annealing process, recrystallization can refine the grain size, remove the bonds created by plastic deformation, and render the texture lean. Thus, the ductility and formability of the annealed sheet dramatically increased compared to the rolled sheet. Experimental results show that recrystallization can occur in the temperature range of 350 ° C to 500 ° C. At a given annealing temperature, recrystallization is complete when the hardness is no longer significantly reduced with an extension of the annealing time.

Since the final mechanical properties are closely related to the annealing temperature and time, B2 alloy sheets are selected to optimize the annealing conditions. Optimized annealing conditions for the alloy sheet were identified by measuring the change in hardness after exposure to different temperatures for different times. Therefore, in order to find the completion time of recrystallization at different annealing temperatures, a hardness test is conducted on B2 alloy sheet samples with different annealing temperatures and annealing times.

The change in hardness as a function of exposure time for the B2 sheet rolled at 450 DEG C and then annealed at different temperatures is shown in FIG. The hardness value was sharply reduced in the first one minute annealing and found to be stable for one hour at 350 占 폚, 0.5 hours at 400 占 폚, 0.5 hours at 450 占 폚, or 0.5 hours at 500 占 폚 for the B2 processing alloy sheet. Thus, the sheet was annealed at 350 DEG C for 1 hour, 400 DEG C for 0.5 hour, 450 DEG C for 0.5 hour, and 500 DEG C for 0.5 hour, and then tested along the rolling direction. As the annealing temperature increased, the yield strength of the B2 alloy sheet decreased as expected, while the strain-hardening index of these alloys slightly increased. The UE and SHE of the B2 alloy sheet were found to decrease after annealing at 500 DEG C for 0.5 hour.

Further, as shown in Table 5, when the annealing temperature is 350 占 폚, the recrystallization time of the B2 alloy sheet is one hour. However, when the annealing temperatures are 400, 450 and 500 ° C, the recrystallization time of the B2 alloy sheet is 0.5 hour for the B2 alloy sheet.

A room temperature tensile test was also performed on B2 alloy sheets annealed at 350 DEG C for 1 hour, 400 DEG C, 450 DEG C and 500 DEG C for 0.5 hour under different conditions. The mechanical properties including the yield strength, UTS, UE, TE, and SHE of the B2 alloy sheet under the different annealing conditions are summarized in Table 6. With respect to the B2 alloy sheet, annealing treatment at 400 DEG C for 0.5 hour, in which a ductility of 38% appeared, proved to be the optimum annealing condition.

Summary of tensile sheets of B2 alloy sheet annealed at different temperatures designation Hot rolling temperature (캜) Yield strength (MPa) UTS (MPa) UE (%) TE (%) SHE B2 400 156 228 19 33 0.21 450 152 224 20 38 0.22 500 130 211 17 23 0.22

Summary of tensile properties of annealed B2 alloy sheets under different conditions designation Annealing conditions Yield strength (MPa) UTS (MPa) UE (%) TE (%) SHE B2 350 ℃ 1 hour 162 228 18 25 0.17 400 ℃ for 0.5 hour 152 224 20 38 0.22 450 DEG C 0.5 hours 137 222 21 36 0.24 500 ° C 0.5 hours 123 219 19 30 0.24

Taking into account the UE and SHE values, hot rolling at 450 ° C and annealing at 0.5 h at 400 ° C for 0.5 hour provides the best formability for both alloys.

conclusion

Overall, it can be concluded from the experimental results that Mg-Ca-Zn- (Zr) based alloys show moderate moldability but can be significantly strengthened by artificial aging treatment. For example, in the annealed state, the yield strength of the Mg-0.8Ca-0.4Zn-0.1Sr-0.4Gd-0.5Zr alloy is only about 137 MPa, but the alloy is increased to 168 MPa .

Further, the inventors of the present invention have found that a sheet formed from a Mg-Zn-Gd-Ca-Zr alloy shows excellent mechanical properties in terms of strength and moldability. The addition of 0.2% Ca to the Mg-1Zn-0.4Gd-0.5Zr alloy revealed that the formed alloy sheet (1.93 LDR to 2.02 LDR) and the strength (141 MPa to 152 MPa) of the formed alloy sheet were remarkably increased. When the Ca content was increased to 0.5%, the yield strength slightly increased from 152 MPa to 155 MPa, but the LDR value decreased from 2.02 to 1.87 as compared with the Mg-1Zn-0.4Gd-0.2Ca-0.5Zr alloy Respectively. As a result, the Ca element is indispensable for improving the moldability and strength of the Mg-Zn-Gd-Ca-Zr alloy sheet, but strict control of the Ca content is necessary. Addition of 0.1% Sr or 0.1% La to the Mg-1Zn-0.4Gd-0.2Ca-0.5Zr alloy increases the strength but decreases the LDR value.

In addition, the Mg-Zn-Gd-Ca-Zr alloy and the Mg-Ca-Zn-Sr- (Gd) -Zr alloy sheet also exhibited sufficient strength and moldability at room temperature. The composition of Mg-0.8Ca-0.4Zn-0.1Sr-0.4Gd-0.5Zr showed the best mechanical properties in terms of yield strength (137 MPa) and moldability (1.83 LDR).

In summary, the present invention is directed to the development of magnesium alloys and thus magnesium alloy sheets which are highly formable. The addition of the alloying element Ca to the Mg-Zn-RE-Zr alloy can remarkably improve the ductility and moldability of each alloy sheet. Particularly, when a small amount of Ca is added to the Mg-Zn-Gd-Zr alloy, a new Mg alloy sheet having high ductility, moldability and relatively good strength can be obtained. In this regard, (1) addition of dilute calcium to the Mg-Zn-Gd-Ca-Zr system can significantly improve ductility and formability; (2) The Mg-Ca-Zn- (Zr) -based alloy showed excellent ductility and moldability by addition of a small amount of alloying elements. The ductility and formability of the sheets formed from these new alloys have been used as impurities and are far superior to AZ31, which can be compared to 6016 alloy sheets, indicating that alloys and corresponding alloy sheets are suitable for many industrial applications.

The inventors believe that the above-described features make the alloy of the present invention particularly suitable for automotive applications. In addition, the alloy of the present invention can be processed by a variety of manufacturing techniques including extrusion, forging, and twin-roll casting.

Those skilled in the art will appreciate that the invention described herein can be embodied in compositions and arrangements of steps other than those in which modifications and variations are specifically described. The present invention is intended to cover all modifications and variations that fall within the spirit and scope of the invention. .

Where the use of the terms "comprises," " including, "" including," or "comprising, " Numerical values, steps, components, or combinations thereof, unless the context clearly dictates otherwise.

Subsequent patent applications may be filed in Australia or abroad based on, or prior to, the present application. It is to be understood that any of the following claims are provided by way of example only and are not intended to limit the scope of what may be claimed in a subsequent application. Features may be added or omitted from the provisional claims in the future to further specify or re-specify the invention or inventions.

Claims (25)

0.1 to 2.0 Zn;
Ca of 0.05 to 1.5;
Zr of 0.1 to 1.0;
A rare earth element of 0 to 1.3 or a mixture thereof containing Gd or Y;
0 to 0.3 Sr;
0 to 0.7 Al;
(% By weight) essentially consisting of magnesium and inevitable impurities of the remainder.
The method according to claim 1,
Wherein the rare earth element mixture comprises gadolinium (Gd) or yttrium (Y) and a rare earth element of the lanthanide series.
3. The method according to claim 1 or 2,
Wherein the rare earth element mixture comprises gadolinium and lanthanum (La).
3. The method according to claim 1 or 2,
Wherein the rare earth element is essentially composed of gadolinium.
Zn: 0.1 to 2.0;
Ca: 0.05 to 1.5;
Zr: 0.1 to 1.0;
Gd: 0 to 1.0;
Sr: 0 to 0.3;
La: 0 to 0.3;
Al: 0 to 0.7; And
(% By weight) essentially consisting of magnesium and inevitable impurities of the remainder.
6. The method according to any one of claims 1 to 5,
Zn: 0.3 to 1.0;
Ca: 0.3 to 1.0;
Zr: 0.2 to 0.7;
Gd: 0.1 to 0.5;
Sr: 0 to 0.2;
La: 0 to 0.2;
Al: 0 to 0.5; And
(% By weight) essentially consisting of magnesium and inevitable impurities of the remainder.
7. The method according to any one of claims 1 to 6,
Zn: 0.5 to 2.0;
Ca: 0.05 to 1.0;
Zr: 0.1 to 1.0;
Gd: 0.05 to 1.0;
Sr: 0 to 0.3;
La: 0 to 0.3;
Al: 0 to 0.7; And
Mg-Zn-Gd-Ca-Zr-based alloy essentially consisting of Mg and unavoidable impurities.
8. The method of claim 7,
Zn: 0.5 to 1.5;
Ca: 0.1 to 0.7;
Zr: 0.2 to 0.7;
Gd: 0.1 to 0.5;
Sr: 0 to 0.2;
La: 0 to 0.2;
Al: 0.2 to 0.5; And
Mg-Zn-Gd-Ca-Zr-based alloy essentially consisting of Mg and unavoidable impurities.
7. The method according to any one of claims 1 to 6,
Ca: 0.3 to 1.5;
Zn: 0.1 to 0.8;
Zr: 0.1 to 1.0;
Gd: 0 to 1.0;
Al: 0 to 0.7;
Sr: 0 to 0.3; And
A Mg-Ca-Zn- (Zr) -based alloy essentially consisting of Mg of the remainder and other inevitable impurities (% by weight).
10. The method of claim 9,
Ca: 0.6 to 1.0;
Zn: 0.3 to 0.5;
Zr: 0.2 to 0.7;
Gd: 0 to 0.5;
Al: 0.2 to 0.5;
Sr: 0 to 0.2; And
A Mg-Ca-Zn- (Zr) -based alloy essentially consisting of Mg of the remainder and other inevitable impurities (% by weight).
In any of the previous claims,
Wherein the total weight percent of the alloy element is less than 4%, preferably less than 3%.
In any of the previous claims,
A magnesium-based processing alloy further comprising Mn of 0.05 to 0.7, preferably 0.1 to 0.5.
In any of the previous claims,
Wherein the magnesium-based alloy comprises incidental impurities less than 0.5% by weight.
In any of the previous claims,
Wherein the magnesium-based alloy comprises an incidental impurity of less than 0.2 wt%.
In any of the previous claims,
Wherein the magnesium-based alloy is selected from Mg-1Zn-0.4Gd-0.2Ca-0.5Zr or Mg-0.8Ca-0.4Zn-0.1Sr-0.4Gd-0.5Zr.
16. A magnesium-based working alloy sheet comprising at least one magnesium-based working alloy according to any one of claims 1 to 15.
A method of producing a magnesium alloy sheet product,
Providing a magnesium alloy melt from the magnesium-based alloy according to any one of claims 1 to 15;
Casting the magnesium alloy melt into a slab or strip having a predetermined thickness;
Homogenizing or preheating the cast slab or strip;
Continuously hot-rolling the homogenized or preheated slab or strip at an appropriate temperature to reduce the thickness of the homogenized slab or strip to produce an alloy sheet product of a predetermined thickness; And
And annealing the alloy sheet product at an appropriate temperature for a period of time.
18. The method of claim 17,
Wherein the casting comprises supplying a magnesium alloy melt between rolls of a twin-roll caster to produce a strip.
The method according to claim 17 or 18,
Wherein the homogenizing or preheating of the cast slab or strip is performed at a temperature between 300 and 500 < 0 > C.
The method according to any one of claims 17 to 19,
The homogenizing or preheating step of the cast slab or strip is then followed by quenching, preferably water quenching.
21. The method according to any one of claims 17 to 20,
Wherein the step of hot rolling is performed at a temperature range of 300 to 550 캜, preferably 350 to 500 캜.
22. The method according to any one of claims 17 to 21,
Wherein the total thickness is reduced by 50 to 95%, preferably by 70 to 80% as a result of the hot rolling step.
23. The method according to any one of claims 17 to 22,
The hot rolling step is performed using a plurality of rolling passes and after each rolling pass the sheet is reheated at a temperature in the range of 350 to 550 占 폚 prior to subsequent rolling to form a magnesium- A method for manufacturing a sheet product.
24. The method according to any one of claims 17 to 23,
Wherein the casting step comprises injecting the magnesium alloy melt into one of a direct chill (DC) caster, a sand caster, or a permanent mold caster, A method for manufacturing a product.
25. The method according to any one of claims 17 to 24,
Further comprising aging the annealed alloy at 150 < 0 > C for at least 1 hour.

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