Disclosure of Invention
In view of the above, the present invention provides an aluminum alloy and a method for preparing the same. The aluminum alloy provided by the invention has high tensile strength and good high-temperature mechanical property.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides an aluminum alloy which comprises the following elements in percentage by mass: fe: 5.8-6.2 wt.%, ce:1.3 to 1.7wt.% and the balance aluminum.
Preferably, the aluminum alloy comprises the following elements in percentage by mass: fe: 5.8-6.2 wt.%, ce:1.5wt.% and balance aluminum.
The invention also provides a preparation method of the aluminum alloy in the technical scheme, which comprises the following steps:
providing Al-Fe-Ce alloy powder;
and carrying out selective laser melting on the Al-Fe-Ce alloy powder, and then carrying out stress relief annealing to obtain the aluminum alloy.
Preferably, the grain diameter of the Al-Fe-Ce alloy powder is 15-53 mu m, and the loose packed density is 1.30-1.45 g/cm 3 。
Preferably, the power of the selective laser melting is 200-300W, and the scanning speed is 400-1600 mm/s.
Preferably, the power of the selective laser melting is 300W, and the scanning speed is 1600mm/s.
Preferably, the temperature of the stress relief annealing is 200-250 ℃, and the holding time is 4-6 h.
Preferably, the scanning distance of the selective laser melting is 100-140 μm, the layer thickness is 25-30 μm, and the scanning strategy is that the rotation angle between adjacent layers is 67 degrees.
Preferably, the substrate for selective laser melting is an Al substrate, and the preheating temperature of the Al substrate is 100 to 150 ℃.
Preferably, the drying is also included before the selective laser melting of the Al-Fe-Ce alloy powder, the drying temperature is 120-140 ℃, and the heat preservation time is 2-4 h.
The invention provides an aluminum alloy which comprises the following elements in percentage by mass: fe: 5.8-6.2 wt.%, ce:1.3 to 1.7wt.% and the balance aluminum.
Aiming at the problems existing in the preparation of Al-Fe alloy by the traditional casting technology and the problem that the application of the traditional aluminum alloy under the high-temperature condition is restricted due to the strengthening phase coarsening phenomenon, the invention provides an alloy proportion which can improve the structure of the Al-Fe alloy, improve the high-temperature mechanical property of the Al-Fe alloy, is suitable for the selective laser melting technology and avoids the generation of acicular and leaf-shaped Al 3 The Fe phase cracks the matrix, causes the deterioration of the performance, and the addition of the Ce element can refine the size of the Al-Fe intermetallic compound and improve the Al 3 The shape of the Fe phase obtains reinforced phase particles in a matrix, so that the strength and the high-temperature mechanical property of the alloy are further improved, the plasticity of the alloy is improved, the high-temperature stability of the alloy is enhanced, the application of the alloy in the field of additive manufacturing is expanded, and an aluminum alloy additive manufacturing material system is enriched.
The invention also provides a preparation method of the aluminum alloy, which comprises the following steps: providing Al-Fe-Ce alloy powder; and carrying out selective laser melting on the Al-Fe-Ce alloy powder, and then carrying out stress relief annealing to obtain the aluminum alloy.
According to the invention, the strength of pure Al under the equilibrium solidification condition is increased along with the increase of Fe content through calculation and analysis, which shows that the strengthening effect of the iron phase is very obvious. Although Al-Fe phase has excellent properties such as high hardness, good high temperature resistance, wear resistance and corrosion resistance, the content of Fe element is too high, which increases the material density, and if the content of Fe element in Al exceeds the limit solid solubility, coarse needle-like Al is generated in the structure 13 Fe 4 Phase, fracture of the matrix, resulting in severe decrease of mechanical properties, with increase of cooling rate, al 13 Fe 4 Equilibrium phase will be metastable Al 6 Fe phase and Al m Fe phase substitution.Al-Fe alloy with Fe content greater than eutectic point component to form metastable Al 6 Fe and Al m The cooling rate required for the Fe phase increases as the Fe content increases. Through SLM forming (selective laser melting technology) of the Al-Fe binary alloy, when a near-eutectic Al-Fe alloy with Fe content of 2.5wt.% is prepared, al in short rods is distributed in the structure 6 Fe is connected to form a net structure; when hypereutectic Al-Fe alloy with 15wt.% Fe content is prepared, leaf-shaped Al is distributed at the edge of the molten pool 13 Fe 4 Phase, spherical metastable Al is distributed in the molten pool 6 An Fe phase. The selective area laser melting technology adopted by the invention has a higher cooling speed than that of a spin casting method, can increase the maximum solid solubility of Fe in Al, enhances the solid solution strengthening effect, reduces the heat affected area in the solidification process and obtains a finer structure.
Detailed Description
The invention provides an aluminum alloy which comprises the following elements in percentage by mass: fe: 5.8-6.2 wt.%, ce:1.3 to 1.7wt.% and the balance aluminum.
In the present invention, the aluminum alloy preferably includes the following elements in percentage by mass: fe: 5.8-6.2 wt.%, ce:1.5wt.% and balance aluminum.
In particular embodiments of the present invention, the mass percent Fe in the aluminum alloy is 5.8wt.%, 6.0wt.%, or 6.2wt.%, and the mass percent Ce is 1.3wt.%, 1.5wt.%, or 1.7wt.%. The method can clarify the structure morphology regulation mechanism of the Ce element on the Al-Fe-Ce alloy under the rapid solidification condition, and clarify the room temperature strengthening mechanism of the Al-Fe-Ce alloy.
The invention also provides a preparation method of the aluminum alloy in the technical scheme, which comprises the following steps:
providing Al-Fe-Ce alloy powder;
and performing selective laser melting on the Al-Fe-Ce alloy powder, and then performing stress relief annealing to obtain the aluminum alloy.
The invention provides an Al-Fe-Ce alloy powder.
In the present invention, the Al-Fe-Ce alloy powder preferably has a particle diameter of 15 to 53 μm and a bulk density of 1.30 to 1.45g/cm 3 。
In the invention, the Al-Fe-Ce alloy powder is preferably dried before selective laser melting, the drying temperature is preferably 120-140 ℃, the heat preservation time is preferably 2-4 h, the drying is used for degassing and removing water, and the drying is preferably carried out in a vacuum drying oven.
The Al-Fe-Ce alloy powder is preferably prepared by adopting an atomic gas atomization method.
The invention preferably observes the morphology and the cross-sectional structure of the powder under a scanning electron microscope.
In the present invention, when observing the cross-sectional structure of the powder, it is preferable to insert a small amount of the powder on an insert block having a diameter of 30mm, sequentially polish the insert block with sand paper having a particle size of 600 mesh or 1000 mesh, and then use SiO 2 And polishing by using the polishing solution.
After the Al-Fe-Ce alloy powder is obtained, the selective laser melting is carried out on the Al-Fe-Ce alloy powder, and then the stress relief annealing is carried out to obtain the aluminum alloy.
According to the invention, the Al-Fe-Ce alloy powder is preferably put into a powder baking cylinder of an SLM printer, and the SLM printer is started to perform selective laser melting.
In the invention, the power of the selective laser melting is preferably 200-300W, and the scanning speed is preferably 400-1600 mm/s. In the present invention, the interval of the selective laser melting is preferably 200mm/s.
The invention preferably selects three laser powers of 200W, 250W and 300W and seven scanning speeds of 400-1600mm/s and 200mm/s interval to carry out orthogonal test, 2 groups of 21 groups of 8 multiplied by 8mm are formed, wherein each group corresponds to different parameters respectively 3 The block sample of (1).
In a specific embodiment of the present invention, the power of the selective laser melting is preferably 300W, and the scanning speed is preferably 1600mm/s.
In the invention, the scanning interval of the selective laser melting is preferably 100-140 μm, the layer thickness is preferably 25-30 μm, and the scanning strategy is preferably that the rotation angle between adjacent layers is 67 degrees.
In the invention, the substrate for selective laser melting is preferably an Al substrate, and the preheating temperature of the Al substrate is preferably 100-150 ℃.
After the selective laser melting is finished, the printed sample piece is separated from the substrate by linear cutting, residual powder is cleaned, the sample piece is sequentially polished by 120-2000 meshes of abrasive paper and then is polished by SiO 2 Polishing the polishing solution, observing the polished polishing solution under an optical microscope, calculating the porosity of the corresponding sample under each parameter through software, and performing subsequent work by adopting the parameter capable of obtaining the sample with the highest density.
According to the invention, the optimal process parameters are determined by controlling the energy density (scanning speed and laser power) of selective laser melting and the distance between scanning lines, so that the defect-free and high-density particle reinforced aluminum matrix composite material is prepared.
In the invention, the temperature of the stress relief annealing is preferably 200-250 ℃, and the holding time is preferably 4-6 h.
After the stress relief annealing, the method preferably further comprises the step of furnace cooling to room temperature.
According to the invention, SEM and EBSD analysis and characterization are preferably carried out on the samples in the deposition state and the annealing state respectively, and the samples for SEM and EBSD test are preferably ground by 120-2000 meshes of sand paper and then are ground by SiO 2 And polishing by using the polishing solution, and preparing a sample for the EBSD test by adopting ion polishing.
After the stress relief annealing is finished, the method preferably further comprises the step of measuring the mechanical property of the part under the optimal process parameters, and preferably comprises the following steps:
(1) Machining the samples before and after stress relief annealing, machining 6 plate-shaped tensile samples from the bottom to the top of the obtained massive metal sample piece along the deposition direction, and machining 1 rod-shaped tensile sample from the columnar metal sample piece;
(2) Respectively testing the mechanical properties of the plate-shaped tensile sample in a deposition state and an annealing state at room temperature;
(3) And (3) testing the mechanical property of the annealed rod-shaped tensile sample at high temperature, wherein the high temperature is 200 or 300 ℃.
In order to further illustrate the present invention, the following will describe in detail the aluminum alloys and the methods for preparing the same provided by the present invention with reference to examples, which should not be construed as limiting the scope of the present invention.
Example 1
First, powder preparation.
(1) The particle diameter is 15 to 53 mu m, the apparent density is 1.30 to 1.45g/cm 3 The Al-Fe-Ce alloy powder of (1), wherein the mass percent of Fe in the Al-Fe-Ce alloy powder is 5.8wt.%, 6.0wt.%, or 6.2wt.%, the mass percent of Ce in the Al-Fe-Ce alloy powder is 1.3wt.%, 1.5wt.%, or 1.7wt.%, and the balance is Al;
(2) And observing the morphology and the cross-sectional structure of the powder under a scanning electron microscope. A small amount of powder is inlaid on an inlaying sample block with the diameter of 30mm, and after being sequentially polished by sand paper with the granularity of 600 meshes and 1000 meshes, siO is adopted 2 And polishing by using the polishing solution.
(3) The powder was subjected to composition and particle size measurement.
Secondly, determining the optimal technological parameters of the selective laser melting
(1) Drawing a three-dimensional graph to be formed through software;
(2) Placing the prepared powder in a vacuum drying oven for drying, degassing and dewatering, wherein the specific process is at 120 ℃, and keeping the temperature for 4 hours;
(3) And putting the powder after vacuum drying into a powder drying cylinder of the SLM printer, starting the SLM printer, and starting printing operation. Respectively selecting three laser powers of 200W, 250W and 300W and seven scanning speeds of 400-1600mm/s and 200mm/s interval to carry out orthogonal test, forming 2 groups of 21 groups of 8 multiplied by 8mm and 8mm respectively corresponding to different parameters 3 The block sample of (1);
(4) Wherein the scanning distance is 100-140 mu m, the layer thickness is 25 mu m, the scanning strategy is that the rotation angle between adjacent layers is 67 degrees, and the preheating temperature of the Al substrate is 100 ℃;
(5) Separating the printed sample piece from the substrate by linear cutting, and cleaning the residual powder;
(6) The sample piece is sequentially polished by 120-2000 meshes of abrasive paper and then is polished by SiO 2 Polishing the polishing solution, observing the polished polishing solution under an optical microscope, calculating the porosity of the corresponding sample under each parameter through software, and performing subsequent work by adopting the parameter capable of obtaining the sample with the highest density;
(7) The software calculation shows that the density of the prepared sample is the highest and is 99.877% when the power is 300W and the scanning speed is 1600mm/s;
(8) Preparing a tensile sample under the optimal process parameters.
And thirdly, observing the microstructure of the sample, and detecting the phase components of the sample.
(1) Performing stress relief annealing on the sample, wherein the specific process system is that the temperature is increased to 200 ℃ along with the furnace, and the temperature is kept for 6 hours and then the sample is cooled along with the furnace;
(2) And respectively carrying out SEM analysis and EBSD analysis characterization on the deposition state sample and the annealing state sample. The samples for SEM and EBSD tests are sequentially polished by 120-2000 meshes of sand paper and then are polished by SiO 2 Polishing ofAnd polishing the solution, and preparing a sample for the EBSD test by adopting ion polishing.
And fourthly, measuring the mechanical property of the part under the optimal process parameters.
(1) And (3) machining a sample obtained by performing stress relief annealing on the formed metal sample, machining 6 plate-shaped tensile samples from the bottom to the top of the massive metal sample along the deposition direction, and machining 1 rod-shaped tensile sample from the columnar metal sample.
(2) Respectively testing the mechanical properties of the plate-shaped tensile sample in a deposition state and an annealing state at room temperature;
(3) And (3) testing the mechanical property of the annealed rod-like tensile sample at high temperature.
Table 1 shows the room-temperature tensile strength test results of Al-Fe-Ce alloys with different element contents, table 2 shows the 200 ℃ tensile strength test results of Al-Fe-Ce alloys with different element contents, and Table 3 shows the 300 ℃ tensile strength test results of Al-Fe-Ce alloys with different element contents.
TABLE 1 room-temperature tensile strength test results of Al-Fe-Ce alloy with different element contents
TABLE 2 tensile strength test results of Al-Fe-Ce alloy with different element contents at 200 DEG C
TABLE 3 tensile strength at 300 ℃ of Al-Fe-Ce alloy with different element contents
FIG. 1 shows Jmatpro softwareThe strength change trend chart of the Al-Fe alloy is calculated along with the increase of the Fe content, and the strength of the pure Al under the equilibrium solidification condition is increased along with the increase of the Fe content, which shows that the strengthening effect of the iron phase is very obvious. Although Al-Fe phase has excellent properties such as high hardness, good high temperature resistance, wear resistance and corrosion resistance, the content of Fe element is too high, which increases the material density, and if the content of Fe element in Al exceeds the limit solid solubility, coarse needle-like Al is generated in the structure 13 Fe 4 Phase, which cracks the matrix, causing severe degradation of mechanical properties.
Fig. 2 is a particle size distribution diagram of Al-Fe-Ce alloy powder (6.0 wt.% Fe, 1.5wt.% Ce, and the balance Al). The particle size of the powder is mainly defined to be 15 to 53 μm.
Fig. 3 is a sectional morphology of Al-Fe-Ce alloy powder (Fe of 6.0wt.%, ce of 1.5wt.%, balance Al), illustrating that fine equiaxed crystals with a size less than 1 μm are visible on the surface and section of the powder, and the grain boundary has a continuous precipitated phase.
FIG. 4 is a design diagram of a printing scheme of the optimal process parameters of the Al-Fe-Ce alloy.
Fig. 5 is a photograph of a molten pool of an Al-Fe-Ce alloy sample (6.0 wt.% Fe, 1.5wt.% Ce, and the balance Al) as deposited under a light mirror, illustrating that the characteristic microstructure of the SLM-molded sample consists of a semi-cylindrical molten pool corresponding to a local melting and rapid solidification region under scanning laser irradiation. The height of the molten pool is 80-110 μm, and the width is 100-150 μm.
Fig. 6 is an EBSD scanning image of an as-deposited Al-Fe-Ce alloy sample (mass% Fe is 6.0wt.%, mass% Ce is 1.5wt.%, and the balance is Al), which illustrates that the inside of the sample has an isomeric structure composed of columnar crystals and equiaxed crystals, and the crystal grain orientation is along the 111 direction.
FIG. 7 shows the tensile test results of Al-Fe-Ce alloy samples under different temperature conditions, wherein 1 is yield strength and 2 is tensile strength.
Example 2
During powder preparation, the mass percent of Fe in the Al-Fe-Ce alloy powder is 6.0wt.%, the mass percent of Ce is 1.5wt.%, and the balance is Al.
The method is the same as the example 1, except that the stress relief annealing is furnace-mounted heating to 250 ℃, and furnace-mounted cooling is carried out after 4 hours of heat preservation.
The aluminum alloy obtained in example 2 had a room-temperature tensile strength of 575MPa, a 200 ℃ tensile strength of 507MPa, and a 300 ℃ tensile strength of 366MPa.
Example 3
During powder preparation, the mass percent of Fe in the Al-Fe-Ce alloy powder is 5.8wt.%, the mass percent of Ce is 1.7wt.%, and the balance is Al.
The method is the same as the example 1, except that the stress relief annealing is furnace-mounted heating to 220 ℃, and furnace-mounted cooling is carried out after 5h of heat preservation.
The aluminum alloy obtained in example 2 had a room-temperature tensile strength of 581MPa, a 200 ℃ tensile strength of 503MPa, and a 300 ℃ tensile strength of 372MPa.
Comparative example 1
The same as example 1, except that the mass% of Fe in the Al-Fe-Ce alloy powder in the first step of powder preparation was 6.87wt.%, the mass% of Ce was 3.95wt.%, and the balance was Al.
The aluminum alloy obtained in comparative example 1 had tensile strength of 502MPa at room temperature, 469MPa at 200 ℃ and 335MPa at 300 ℃.
Comparative example 2
The method is the same as the example 2, except that the stress relief annealing is furnace-mounted heating to 190 ℃, and furnace-mounted cooling is carried out after the temperature is kept for 7 hours.
The aluminum alloy obtained in comparative example 2 had a tensile strength of 560MPa at room temperature, 498MPa at 200 ℃ and 347MPa at 300 ℃.
Comparative example 3
The method is the same as the example 2, except that the stress relief annealing is furnace-mounted heating to 260 ℃, and furnace-mounted cooling is carried out after 3h of heat preservation.
The aluminum alloy obtained in comparative example 3 had a room temperature tensile strength of 553MPa, a 200 ℃ tensile strength of 488MPa and a 300 ℃ tensile strength of 340MPa.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that, for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be construed as the protection scope of the present invention.