CN111172445B - High-entropy alloy with double-layer close-packed hexagonal structure - Google Patents

High-entropy alloy with double-layer close-packed hexagonal structure Download PDF

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CN111172445B
CN111172445B CN202010018097.4A CN202010018097A CN111172445B CN 111172445 B CN111172445 B CN 111172445B CN 202010018097 A CN202010018097 A CN 202010018097A CN 111172445 B CN111172445 B CN 111172445B
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rare earth
entropy alloy
pressure
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CN111172445A (en
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于鹏飞
李工
刘日平
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Yanshan University
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Yanshan University
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C30/00—Alloys containing less than 50% by weight of each constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/02—Making non-ferrous alloys by melting

Abstract

The invention discloses a high-entropy alloy with a double-layer close-packed hexagonal structure, which belongs to the technical field of rare earth alloy materials and comprises the following components of LaxCexPrxNdxWherein x is atomic number percent x-25, or LaxCexPrxNdxSmxWherein x is the atomic number percentage x is 20, and the alloy is smelted by a high vacuum arc smelting furnace under the protection of high-purity argon; the high-entropy alloy is prepared from light rare earth simple substances of lanthanum, cerium, praseodymium, neodymium and samarium (La, Ce, Pr, Nd and Sm), an X-ray diffraction spectrum of the high-entropy alloy is obtained through an X-ray diffractometer, and the crystal structure of the prepared light rare earth high-entropy alloy is determined to be a double-layer close-packed hexagonal structure. The in-situ high-pressure synchrotron radiation X-ray technology is utilized to determine that the high-pressure phase structure has two high-pressure phase structures of face-centered cubic (fcc) and distorted face-centered cubic (dfcc) under high pressure.

Description

High-entropy alloy with double-layer close-packed hexagonal structure
Technical Field
The invention relates to the technical field of rare earth alloy materials, in particular to a double-layer close-packed hexagonal high-entropy alloy completely composed of light rare earth.
Background
Rare earth elements have similar crystal structures, similar atomic radii and electronegativities, and can form infinite solid solution alloys with each other. Therefore, the rare earth elements are alloyed according to equal atomic percentage, so that the rare earth high-entropy alloy can be obtained, has excellent magnetic performance, is a good magnetic refrigeration material, and has attracted wide attention of material science workers. Seventeen rare earth elements are generally divided into two groups according to the atomic electron shell structure and physicochemical properties of the rare earth elements, and the characteristics that the different properties can be generated by the coexistence situation and different ionic radii of the rare earth elements in minerals: light rare earth: lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium; heavy rare earth: gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium and yttrium. At present, the research on rare earth high-entropy alloys mainly comprises heavy rare earth high-entropy alloys composed of heavy rare earth (Y, Gd, Tb, Dy, Ho, Er, Tm and Lu) elements, such as YGdTbDyLu, GdTbDyTmLu, DyGdHoTbY, GdDyErHoTb, DyGdHoTbY and the like, wherein the heavy rare earth high-entropy alloys have a close-packed hexagonal crystal structure. The crystal structure of the heavy rare earth high-entropy alloy is not changed by adding a small amount of light rare earth elements, and GdHoLaTbY, LaGdHoYCe and the like still keep a close-packed hexagonal structure. The light rare earth elements La, Pr, Nd and Sm all have double-layer close-packed hexagonal structures at normal temperature and normal pressure, and Ce has two structures of face-centered cubic (fcc) and double-layer close-packed hexagonal (dhcp).
Under pressure, rare earth simple substance has rich phase transition, and due to the characteristic of conduction band d electrons, trivalent rare earth elements show similar crystal structure change process from La to Lu (except Eu and Yb) along with the increase of pressure: hcp → Sm-type → dhcp → fcc, and its phase transition pressure increases with increasing atomic number. As the pressure increases, a distorted fcc structure will result. With further increase of pressure, part of the rare earth elements will transform into a structure of low symmetry with volume collapse. The heavy rare earth high-entropy alloy ygdddyhotb has a similar phase transition process at high pressure, however, high-entropy alloys formed entirely of light rare earth elements and phase structures thereof at high pressure are rarely reported.
Disclosure of Invention
The invention aims to provide a high-entropy alloy with a double-layer close-packed hexagonal structure with pressure-induced polymorphic transformation.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a high-entropy alloy with hexagonal close-packed structure is prepared from LaxCexPrxNdxWherein x is atomic number percentage x-25.
The technical scheme of the invention is further improved as follows: laxCexPrxNdxThe alloy has both face centered cubic and twisted face centered cubic structures under high pressure.
The technical scheme of the invention is further improved as follows: the preparation method comprises the following steps:
(1) weighing La with the purity of 99.5-99.9 wt% according to equal atomic percentage: 25%, Ce: 25%, Pr: 25%, Nd: 25% of the raw material;
(2) and uniformly mixing the raw material components, putting the mixture into a high-vacuum arc melting furnace for melting, melting for 4-5 times under the protective atmosphere of high-purity argon, and cooling in a water-cooled copper mold to obtain the alloy button ingot.
The technical scheme of the invention is further improved as follows: the detection method comprises the following steps:
step a, embedding the alloy button ingot into a sample with the size of phi 5mm multiplied by 5mm by using a metallographic sample embedding machine, grinding the surface of the sample by using metallographic abrasive paper of 400#, 800#, 1200# and 2000# in sequence, and polishing the sample;
b, measuring the X-ray diffraction spectrum of the light rare earth high-entropy alloy by using an X-ray diffractometer, wherein the scanning angle range is 20-100 ℃, and the scanning speed is 4 DEG/min;
and c, grinding the alloy ingot into a sheet with the thickness of 30 microns, cutting the sheet into small pieces by using a scalpel, selecting the small pieces with the size of 50-80 microns under a microscope, loading the small pieces into a T301 seal cushion sample cavity with the diameter of phi 100 microns, providing high pressure for a top anvil by using silicon oil as a pressure transmission medium through diamond, and obtaining the structure of the light rare earth high-entropy alloy under the high pressure by adopting in-situ high-pressure synchrotron radiation X-rays.
A high-entropy alloy with hexagonal close-packed structure is prepared from LaxCexPrxNdxSmxWherein x is atomic number percentage x-20.
The technical scheme of the invention is further improved as follows: la20Ce20Pr20Nd20Sm20The alloy has both face centered cubic and twisted face centered cubic structures under high pressure.
The technical scheme of the invention is further improved as follows: the preparation method comprises the following steps:
(1) weighing La with the purity of 99.5-99.9 wt% according to equal atomic percentage: 20%, Ce: 20%, Pr: 20%, Nd: 20%, Sm: 20 percent of the raw material is used as the raw material;
(2) and uniformly mixing the raw material components, putting the mixture into a high-vacuum arc melting furnace for melting, melting for 4-5 times under the protective atmosphere of high-purity argon, and cooling in a water-cooled copper mold to obtain the alloy button ingot.
The technical scheme of the invention is further improved as follows: the detection method comprises the following steps:
step A, embedding the alloy button ingot into a sample with the size of phi 5mm multiplied by 5mm by using a metallographic sample embedding machine, grinding the surface of the sample by using metallographic abrasive paper of No. 400, No. 800, No. 1200 and No. 2000 in sequence, and polishing the sample;
step B, measuring the X-ray diffraction spectrum of the light rare earth high-entropy alloy by using an X-ray diffractometer, wherein the scanning angle range is 20-100 ℃, and the scanning speed is 4 DEG/min;
and step C, grinding the alloy ingot into a sheet with the thickness of 30 microns, cutting the sheet into small pieces by using a scalpel, selecting the small pieces with the size of 50-80 microns under a microscope, loading the small pieces into a T301 seal cushion sample cavity with the diameter of phi 100 microns, providing high pressure to a top anvil by using silicon oil as a pressure transmission medium, and obtaining the structure of the light rare earth high-entropy alloy under the high pressure by using in-situ high-pressure synchrotron radiation X-rays.
Due to the adoption of the technical scheme, the invention has the technical progress that:
la in the present inventionxCexPrxNdxRare earth high entropy alloys wherein x is 25 atomic percent x, or LaxCexPrxNdxSmxWherein x is the atomic number percentage x of 20 and is completely composed of light rare earth elements, breaks through the convention that the prior rare earth high-entropy alloy is mainly composed of heavy rare earth elements, provides a new idea for the development of the rare earth high-entropy alloy, and promotes the application of the rare earth high-entropy alloy in the industrial field.
The light rare earth high-entropy alloy has a double-layer close-packed hexagonal (dhcp) structure at normal temperature and normal pressure, and has two structures of face-centered cubic (fcc) and distorted face-centered cubic (dfcc) at high pressure.
Drawings
FIG. 1 is alloy La25Ce25Pr25Nd25X-ray diffraction pattern of the cast ingot under normal temperature and normal pressure;
FIG. 2 is alloy La20Ce20Pr20Nd20Sm20X-ray diffraction pattern of the cast ingot under normal temperature and normal pressure;
FIG. 3 is alloy La25Ce25Pr25Nd25X-ray diffraction patterns at high pressure;
FIG. 4 is alloy La20Ce20Pr20Nd20Sm20X-ray diffraction pattern at high pressure.
Detailed Description
The present invention will be described in further detail with reference to the following examples:
example one (see FIGS. 1 and 3)
A high-entropy alloy with hexagonal close-packed structure is prepared from LaxCexPrxNdxWherein x is atomic number percentage x-25. LaxCexPrxNdxThe alloy has both face centered cubic (fcc) and distorted face centered cubic (dfcc) structures at high pressures.
High-entropy alloy La with double-layer close-packed hexagonal structure25Ce25Pr25Nd25The preparation method comprises the following steps:
(1) weighing La: 25%, Ce: 25%, Pr: 25%, Nd: 25 percent of the rare earth metal is used as a raw material, and the purity of the light rare earth metal is within the range of 99.5 to 99.9 weight percent;
(2) and uniformly mixing the raw material components, putting the mixture into a high-vacuum arc melting furnace for melting, melting under the protective atmosphere of high-purity argon, repeatedly turning the alloy ingot for 4-5 times in the melting process to improve the uniformity of the alloy components, and cooling in a water-cooling copper mold to obtain the alloy button ingot.
High-entropy alloy La with double-layer close-packed hexagonal structure25Ce25Pr25Nd25The detection method comprises the following steps:
step a, embedding the alloy button ingot into a sample with the size of phi 5mm multiplied by 5mm by using a metallographic sample embedding machine, grinding the surface of the sample by using metallographic abrasive paper of 400#, 800#, 1200# and 2000# in sequence, and polishing the sample;
b, measuring the X-ray diffraction spectrum of the light rare earth high-entropy alloy by using an X-ray diffractometer, wherein the scanning angle range is 20-100 ℃, and the scanning speed is 4 DEG/min;
step c, grinding the alloy ingot into a sheet with the thickness of 30 microns, cutting the sheet into small pieces by using a scalpel, selecting the small pieces with the size of 50-80 microns under a microscope, loading the small pieces into a T301 seal cushion phi 100 micron sample cavity, placing the seal cushion on a diamond anvil, and providing high pressure for the diamond anvil by using silicon oil as a pressure transmission medium; in a Beijing high-pressure synchrotron radiation device 4W2 high-pressure station of Chinese academy of sciences, the structure of the light rare earth high-entropy alloy under high pressure is obtained by adopting in-situ high-pressure synchrotron radiation X-rays.
EXAMPLE two (see FIGS. 2 and 4)
High-entropy alloy with double-layer close-packed hexagonal structure and preparation method thereofComponent (A) is LaxCexPrxNdxSmxWherein x is atomic number percentage x-20. High-entropy alloy La with double-layer close-packed hexagonal structure20Ce20Pr20Nd20Sm20Both face centered cubic (fcc) and distorted face centered cubic (dfcc) structures at high pressures.
High-entropy alloy La with double-layer close-packed hexagonal structure20Ce20Pr20Nd20Sm20The preparation method comprises the following steps:
(1) weighing La with the purity of 99.5-99.9 wt% according to equal atomic percentage: 20%, Ce: 20%, Pr: 20%, Nd: 20%, Sm: 20 percent of the raw material is used as the raw material;
(2) and uniformly mixing the raw material components, putting the mixture into a high-vacuum arc melting furnace for melting, melting for 4-5 times under the protective atmosphere of high-purity argon, and cooling in a water-cooled copper mold to obtain the alloy button ingot.
High-entropy alloy La with double-layer close-packed hexagonal structure20Ce20Pr20Nd20Sm20The detection method comprises the following steps:
step A, embedding the alloy button ingot into a sample with the size of phi 5mm multiplied by 5mm by using a metallographic sample embedding machine, grinding the surface of the sample by using metallographic abrasive paper of No. 400, No. 800, No. 1200 and No. 2000 in sequence, and polishing the sample;
step B, measuring the X-ray diffraction spectrum of the light rare earth high-entropy alloy by using an X-ray diffractometer, wherein the scanning angle range is 20-100 ℃, and the scanning speed is 4 DEG/min;
and step C, grinding the alloy ingot into a sheet with the thickness of 30 microns, cutting the sheet into small pieces by using a scalpel, selecting the small pieces with the size of 50-80 microns under a microscope, loading the small pieces into a T301 seal cushion sample cavity with the diameter of phi 100 microns, providing high pressure to a top anvil by using silicon oil as a pressure transmission medium, and obtaining the structure of the light rare earth high-entropy alloy under the high pressure by using in-situ high-pressure synchrotron radiation X-rays.
The invention adopts a high vacuum arc melting furnace to prepare the La component25Ce25Pr25Nd25And La20Ce20Pr20Nd20Sm20Light rare earthThe high-entropy alloy is measured by an X-ray diffractometer, and the crystal structure of the prepared light rare earth high-entropy alloy is determined to be a double-layer close-packed hexagonal (dhcp) structure by diffraction spectrum calibration.
The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments, and any other embodiments obtained by changing, combining and simplifying the basic principle of the present invention belong to the protection scope of the present application.

Claims (1)

1. A high-entropy alloy with a double-layer close-packed hexagonal structure is characterized in that: the component is LaxCexPrxNdxSmxWherein x is atomic number percentage x ═ 20;
La20Ce20Pr20Nd20Sm20the alloy has two structures of face-centered cubic and twisted face-centered cubic under high pressure;
the preparation method comprises the following steps:
(1) weighing La with the purity of 99.5-99.9 wt% according to equal atomic percentage: 20%, Ce: 20%, Pr: 20%, Nd: 20%, Sm: 20 percent of the raw material is used as the raw material;
(2) uniformly mixing the raw material components, putting the mixture into a high-vacuum arc melting furnace for melting, melting for 4-5 times under the protective atmosphere of high-purity argon, and cooling in a water-cooled copper mold to obtain an alloy button ingot;
the detection method comprises the following steps:
step A, embedding the alloy button ingot into a sample with the size of phi 5mm multiplied by 5mm by using a metallographic sample embedding machine, grinding the surface of the sample by using metallographic abrasive paper of No. 400, No. 800, No. 1200 and No. 2000 in sequence, and polishing the sample;
step B, measuring the X-ray diffraction spectrum of the light rare earth high-entropy alloy by using an X-ray diffractometer, wherein the scanning angle range is 20-100 ℃, and the scanning speed is 4 DEG/min;
and step C, grinding the alloy ingot into a sheet with the thickness of 30 microns, cutting the sheet into small pieces by using a scalpel, selecting the small pieces with the size of 50-80 microns under a microscope, loading the small pieces into a T301 seal cushion sample cavity with the diameter of phi 100 microns, providing high pressure to a top anvil by using silicon oil as a pressure transmission medium, and obtaining the structure of the light rare earth high-entropy alloy under the high pressure by using in-situ high-pressure synchrotron radiation X-rays.
CN202010018097.4A 2020-01-08 2020-01-08 High-entropy alloy with double-layer close-packed hexagonal structure Active CN111172445B (en)

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