A method for improving the strength of laser selectively melted AlSi10Mg alloy

Abstract

The present invention provides a method for improving laser selective melting of AlSi 10 The invention relates to a method for improving the strength of Mg alloy, and belongs to the technical field of additive manufacturing materials. 10 The Mg alloy is continuously cooled from room temperature to ‑170-‑150°C in the furnace and kept warm for 0-30 minutes, and then placed in an air circulation heat treatment furnace at 150-170°C for 50-70 minutes; and kept warm in an air circulation heat treatment furnace at 150-170°C for 0-320 minutes. This is to reduce the residual stress while improving its strength. Due to the extremely high solidification rate in the laser selective melting process, most of the alloy elements in the alloy structure are dissolved in the aluminum matrix to form a supersaturated solid solution. Heat treating the alloy in the temperature range of 150-170°C can promote the dispersed precipitation of GP zone or β″(Mg2Si) strengthening phase in the structure. This precipitation phase coherent with the matrix can achieve precipitation strengthening effect, thereby improving the strength of the alloy.

Description

Technical Field

[0001] The invention relates to a method for improving the strength of laser selectively melted AlSi10Mg alloy, belonging to the technical field of additive manufacturing materials. Background Art

[0002] In recent years, metal additive manufacturing technology represented by laser selective melting has developed rapidly. However, due to the high cooling rate, large temperature gradient, and complex cyclic heat conduction during laser selective melting, large residual stress usually exists in the deposited alloy, which seriously affects the fatigue performance and stress corrosion resistance of the material. Therefore, most alloy materials formed by laser selective melting need to be stress relieved.

[0003] At present, the aluminum alloy widely used in the field of additive manufacturing is AlSi 10 Mg, which has good adaptability to laser selective melting process, has been widely used in the forming of aluminum alloy parts in additive manufacturing. At present, most of them use annealing treatment at 270-300℃ for 2-3 hours to reduce the deposition of AlSi 10 Mg alloy (i.e. AlSi 10 However, this treatment process will cause the room temperature tensile strength and yield strength of the annealed alloy to decrease significantly (by about 34% to 45%), making additive manufacturing of AlSi 10 Mg alloys are difficult to meet the needs of high-load structural parts. Therefore, it is necessary to develop new heat treatment processes to reduce residual stress and improve strength. Summary of the invention

[0004] In order to reduce the laser selective melting of AlSi 10 The present invention provides a method for reducing the residual stress of the deposited Mg alloy and improving the room temperature tensile strength and yield strength. 10 Method for improving residual stress and strength of Mg alloy, the method can reduce laser selective melting AlSi 10 The residual stress of Mg alloy is reduced while improving the room temperature tensile strength and yield strength.

[0005] The object of the present invention is achieved through the following technical solutions:

[0006] A method for improving the strength of laser selectively melted AlSi10Mg alloy, the method comprising the following steps:

[0007] (1) placing the deposited AlSi10Mg alloy in a cold treatment device, introducing liquid nitrogen or liquid argon to continuously cool the alloy from room temperature to -170 to -150°C and keep the temperature for 0 to 30 minutes, and then placing the alloy in an air circulation heat treatment furnace at 150 to 170°C and keeping the temperature for 50 to 70 minutes;

[0008] (2) Keep the temperature in an air circulation heat treatment furnace at 150-170°C for 0-320 min, and air cool to room temperature.

[0009] Furthermore, the deposited AlSi10Mg alloy refers to the AlSi10Mg alloy formed by laser selective melting.

[0010] Furthermore, the AlSi10Mg alloy formed by laser selective melting is prepared by the following method: AlSi10Mg atomized powder with a particle size of 20 to 65 μm is dried in an explosion-proof drying oven, then printed and formed using laser selective melting equipment, and the formed alloy is removed by wire cutting to obtain laser selective melting AlSi10Mg alloy.

[0011] Furthermore, a chessboard scanning strategy is adopted during forming, with a laser power of 300-450 W, a scanning rate of 800-1500 mm / s, a powder layer thickness of 20-60 μm, and an overlap spacing of 0.1-0.2 mm;

[0012] Furthermore, argon gas is used for protection during the forming process, and the oxygen content of the atmosphere is controlled to be less than 100 ppm.

[0013] Furthermore, the drying temperature is 90 to 170° C., and the drying time is 0.5 to 3 hours.

[0014] Furthermore, the method comprises: repeating step (1) 1-2 times.

[0015] Furthermore, the room temperature tensile strength of the treated AlSi10Mg alloy is 490-525 MPa; the yield strength of the AlSi10Mg alloy is 285-335 MPa.

[0016] Furthermore, the cold treatment equipment is a cryogenic box or a constant temperature box.

[0017] Beneficial effects of the present invention:

[0018] The present invention provides a method for reducing the laser selective melting of AlSi 10 Method for improving residual stress and strength of Mg alloy, the present invention is based on laser selective melting technology and AlSi 10The microstructure characteristics of Mg alloys are targeted at the large residual stress of the material, so as to reduce the residual stress and improve its strength at the same time. Due to the extremely high solidification rate in the laser selective melting process, most of the alloy elements in the alloy structure are dissolved in the aluminum matrix to form a supersaturated solid solution. Heat treatment of the alloy in the temperature range of 150-170°C can promote the dispersion and precipitation of GP zone or β″(Mg2Si) strengthening phase in the structure. This precipitation phase coherent with the matrix can achieve precipitation strengthening effect, thereby improving the strength of the alloy.

[0019] The method of the present invention can effectively reduce the laser selective melting of AlSi 10 The residual stress of the deposited Mg alloy is reduced by about 68% to 79%, while the room temperature tensile strength of the alloy is increased by about 2.7% to 9.5% and the yield strength is increased by about 9.7% to 26.1%. Compared with stress relief annealing, this method can reduce the residual stress while increasing the strength (about twice that of the former), effectively improving the mechanical properties and helping to solve the problem of laser selective melting of AlSi 10 The problem of severe strength loss of Mg alloy after stress relief treatment. It is a new type of material suitable for laser selective melting of AlSi 10 Post-treatment methods of Mg alloys. DETAILED DESCRIPTION

[0020] The method of the present invention will be described in further detail below in conjunction with specific examples. It should be understood that the following examples are only exemplary descriptions and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0021] A method for improving laser selective melting of AlSi 10 A method for improving the strength of a Mg alloy, the method comprising the steps of:

[0022] (1) placing the deposited AlSi10Mg alloy in a deep cold box or a constant temperature box, introducing liquid nitrogen or liquid argon to continuously cool the alloy from room temperature to -170 to -150°C and keep it at that temperature for 0 to 30 minutes, and then placing the alloy in an air circulation heat treatment furnace at 150 to 170°C and keeping it at that temperature for 50 to 70 minutes; the deposited AlSi10Mg alloy refers to the AlSi10Mg alloy formed by laser selective melting.

[0023] The AlSi10Mg alloy formed by laser selective melting is prepared by the following method: drying AlSi10Mg atomized powder with a particle size of 20 to 65 μm in an explosion-proof drying oven, then printing and forming using laser selective melting equipment, and removing the formed alloy by wire cutting to obtain laser selective melting AlSi10Mg alloy. A chessboard scanning strategy is adopted during forming, with a laser power of 300 to 450 W, a scanning rate of 800 to 1500 mm / s, a powder layer thickness of 20 to 60 μm, and an overlap spacing of 0.1 to 0.2 mm; argon is used for protection during the forming process, the oxygen content of the atmosphere is controlled to be less than 100 ppm, the drying temperature is 90 to 170°C, and the drying time is 0.5 to 3 hours.

[0024] Step (1) can be repeated 1-2 times for better effect.

[0025] (2) Keep the temperature in an air circulation heat treatment furnace at 150-170°C for 0-320 min, and air cool to room temperature.

[0026] The room temperature tensile strength of the treated AlSi10Mg alloy is 490-525 MPa; the yield strength of the AlSi10Mg alloy is 285-335 MPa.

[0027] Preparation Example 1

[0028] AlSi with a particle size of 20 to 63 μm 10 The Mg atomized powder was dried in an explosion-proof drying oven at 120°C for 1.5 hours. Then, it was printed and formed using laser selective melting equipment. During the forming process, a chessboard scanning strategy was adopted, with a laser power of 370W, a scanning rate of 1000mm / s, a powder layer thickness of 30μm, and an overlap spacing of 0.12mm. Argon was used for protection during the forming process, and the oxygen content of the atmosphere was controlled to be less than 100ppm. The formed alloy was removed by wire cutting to obtain laser selective melting AlSi 10 Mg alloy.

[0029] Embodiment 1:

[0030] The AlSi prepared in Example 1 was selectively melted by laser 10 Mg alloy is processed, and the process is as follows:

[0031] S1: Place the deposited alloy in a cryogenic box at room temperature, introduce liquid nitrogen to control the temperature of the thermostat and the alloy at -160°C, and take it out when it reaches the temperature. After taking it out, place the alloy in an air circulation heat treatment furnace at 160°C for insulation for 60 minutes, and air cool it.

[0032] S2: The alloy obtained in step S1 is placed in an air circulation heat treatment furnace at 160°C for 300 min and air-cooled.

[0033] Embodiment 2:

[0034] The AlSi prepared in Example 1 was selectively melted by laser 10 Mg alloy is processed, and the process is as follows:

[0035] S1: Place the deposited alloy in a thermostat at room temperature, introduce liquid nitrogen to control the temperature of the thermostat and the alloy at -160°C, and take it out when it reaches the temperature. After taking it out, place the alloy in an air circulation heat treatment furnace at 160°C for insulation for 60 minutes, and air cool it.

[0036] S2: Repeat step S1 once.

[0037] Embodiment 3:

[0038] The AlSi prepared in Example 1 was selectively melted by laser 10 Mg alloy is processed, and the process is as follows:

[0039] S1: Place the deposited alloy in a thermostat at room temperature, introduce liquid nitrogen to control the temperature of the thermostat and the alloy at -160°C, and take it out when it reaches the temperature. After taking it out, place the alloy in an air circulation heat treatment furnace at 160°C for insulation for 60 minutes, and air cool it.

[0040] S2: Repeat step S1 once.

[0041] S3: The alloy from step S2 is placed in an air circulation heat treatment furnace at 160° C. for 240 min and air-cooled.

[0042] Embodiment 4:

[0043] The AlSi prepared in Example 1 was selectively melted by laser 10 Mg alloy is processed, and the process is as follows:

[0044] S1: Place the deposited alloy in a thermostat at room temperature, introduce liquid nitrogen to control the temperature of the thermostat and the alloy at -160°C, and take it out when it reaches the temperature. After taking it out, place the alloy in an air circulation heat treatment furnace at 160°C for insulation for 60 minutes, and air cool it.

[0045] S2: Repeat step S1 twice.

[0046] Embodiment 5:

[0047] The AlSi prepared in Example 1 was selectively melted by laser 10 Mg alloy is processed, and the process is as follows:

[0048] S1: Place the deposited alloy in a thermostat at room temperature, introduce liquid nitrogen to control the temperature of the thermostat and the alloy at -160°C, and take it out when it reaches the temperature. After taking it out, place the alloy in an air circulation heat treatment furnace at 160°C for insulation for 60 minutes, and air cool it.

[0049] S2: Repeat step S1 twice.

[0050] S3: The alloy from step S2 is placed in an air circulation heat treatment furnace at 160° C. for 180 min and air-cooled.

[0051] Comparative Example 1:

[0052] The AlSi prepared in Example 1 was selectively melted by laser 10 Mg alloy is subjected to stress relief annealing treatment, and the process is as follows:

[0053] S1: The deposited alloy is placed in an air circulation heat treatment furnace at room temperature at 300°C for 120 min and then air-cooled.

[0054] Test Example 1:

[0055] The tensile strength (R m ) and yield strength (R p0.2 ), the results are shown in Table 1; Raman spectroscopy tests were performed on the alloys in each state to test AlSi 10 The Raman spectrum curve of Si phase in Mg alloy is fitted by PsdVoigt1 function to complete the statistics of Raman peak position of Si phase. The Raman peak position of Si phase in each state of alloy is compared with the standard Raman peak position of Si phase in stress-free state (520cm -1 ) The relative Raman frequency shift of Si phase in different states was calculated, and the results are shown in Table 2. Since the relative Raman frequency shift of Si phase has the following proportional relationship with residual stress:

[0056] σ=-425·Δw

[0057] In the formula, σ is the residual stress and Δw is the relative Raman frequency shift. Therefore, the residual stress changes of alloys in different states can be compared based on the relative Raman frequency shift of Si phase in alloys in different states.

[0058] The results show that compared with the deposited state, the residual stress of the alloy in the embodiment decreased by about 68% to 79%, the tensile strength increased by 2.7% to 9.5%, and the yield strength increased by 9.7% to 26.1%, achieving the effect of reducing residual stress and increasing strength. Compared with stress annealing treatment, this method has higher strength while reducing residual stress, with the tensile strength being about 1.9 times that of the former and the yield strength being about 2 times that of the former. This shows that this method can effectively solve the problem of severe strength loss after stress relief treatment of laser selective melting AlSi10Mg alloy.

[0059] Table 1 Tensile strength and yield strength of alloy materials in deposited state, examples and comparative examples

[0060]

[0061] Table 2 Raman peak position and relative Raman frequency shift of Si phase in deposited state, examples and comparative examples alloy materials

[0062]

[0063]

[0064] The above is an explanation of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method to improve laser selective melting of AlSi 10 A method for improving the strength of a Mg alloy, characterized in that The method comprises the following steps: (1) Deposited AlSi 10 The Mg alloy is placed in a thermostatic box, and liquid nitrogen or liquid argon is introduced to continuously cool the alloy from room temperature to -170~-160℃ and keep the temperature for 0~30min. Then, the alloy is placed in an air circulation heat treatment furnace at 150~170℃ and kept for 50~70min. (2) Keep the temperature in an air circulation heat treatment furnace at 160-170°C for 0-320 min, and air cool to room temperature; the room temperature tensile strength of AlSi10Mg alloy is 490-525 MPa, and the yield strength is 285-335 MPa; The deposited AlSi 10 Mg alloy refers to AlSi formed by laser selective melting 10 Mg alloys; The AlSi10Mg alloy formed by laser selective melting is prepared by the following method: AlSi 10 The Mg atomized powder is dried in an explosion-proof drying oven, and then printed and formed using a laser selective melting device. The formed alloy is removed by wire cutting to obtain laser selective melting AlSi 10 Mg alloys; The chessboard scanning strategy is adopted during forming, with laser power of 300~450W, scanning rate of 800~1500mm / s, powder layer thickness of 20~60μm, and overlap spacing of 0.1~0.2mm; The forming process is protected by argon gas and the oxygen content in the atmosphere is controlled to be less than 100ppm.

2. A method for improving laser selective melting of AlSi according to claim 1 10 A method for improving the strength of a Mg alloy, characterized in that The drying temperature is 90~170℃, and the drying time is 0.5~3h.

3. A method for improving laser selective melting of AlSi according to claim 1 10 A method for improving the strength of a Mg alloy, characterized in that The method comprises: the step (1) is repeated 1-2 times.

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