A method for 3D printing FeMnSi shape memory alloys with a wide laser energy input range

Abstract

The present invention discloses a method for 3D printing an FeMnSi-based shape memory alloy over a wide laser energy input range, comprising the following steps: 1. preparing a mixed powder characterized by high Co and high Si content; and 2. 3D printing the mixed powder into a FeMnSi-based alloy printout with a significant shape memory effect. The present invention proposes adding Co while increasing Si content, effectively reducing the Cr equivalent and Ni equivalent ratios, avoiding the formation of a harmful bcc phase that is detrimental to the shape memory effect, while not compromising the fcc-hcp phase transformation mechanism that leads to the shape memory effect. Thus, even with relatively low energy input, printouts substantially free of bcc phase components and exhibiting a significant shape memory effect can be produced. This broadens the range of laser energy required for printing, significantly expanding the process freedom for 3D printing of FeMnSi-based shape memory alloys and laying the foundation for the preparation of 3D-printed FeMnSi-based shape memory elements with complex shapes.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal additive manufacturing, and specifically relates to a method for 3D printing FeMnSi-based shape memory alloys with a wide laser energy input range. Background Art

[0002] FeMnSi shape memory alloys, typically composed of Fe, Mn, Cr, Ni, and Si, exhibit a remarkable shape memory effect. This effect is driven by a deformation-induced fcc-hcp (face-centered cubic to hexagonal close-packed) phase transition and a reverse hcp-fcc phase transition upon heating, ultimately leading to the deformation's return to its original shape. With a room temperature prestrain of 5%, these alloys can recover up to 2.5%-3% of their original strain upon heating. Their low-temperature strength is significantly higher than that of NiTi shape memory alloys, making them promising candidates for reusable low-temperature intelligent load-bearing, energy storage, and cushioning components in aerospace, robotics, and other fields. Because these intelligent load-bearing, energy storage, and cushioning components typically require complex geometries or porous structures, conventional casting and rolling processes are difficult to fabricate. Therefore, the greater manufacturing flexibility offered by metal powder bed selective laser melting (SLM) 3D printing is required to fabricate these complex FeMnSi shape memory alloy components. However, since metal powder bed selective laser melting 3D printing uses a micron-diameter laser beam to melt metal powder in the powder bed to form a micron-sized molten pool and then solidify it into a dense solid, which continuously accumulates into the shape required for the component, the molten pool cools very quickly. However, due to the Cr equivalent (Cr eq ) and Ni equivalent (Ni eq ) is greater than 1.5(Cr eq and Ni eq Hull calculation formula: Cr eq =Cr+0.48Si;Ni eq =Ni+0.11Mn+0.41Co), which tends to preferentially form a bcc (body-centered cubic) phase during cooling, which then transforms into an fcc phase. Due to the high cooling rate of laser 3D printing, the primary bcc phase does not have sufficient time to transform into an fcc phase, resulting in a large amount of residual bcc phase in the printed part. Since the bcc phase does not participate in the shape memory effect, this is detrimental to the shape memory effect of the printed part. Existing reports have typically used methods to eliminate the detrimental bcc phase by increasing the printing input energy to reduce the cooling rate, such as significantly increasing the laser power. However, this method can easily lead to the formation of keyhole defects during printing. Furthermore, when printing complex-shaped components, excessively high laser power can cause defects such as component deformation or large dimensional errors.

[0003] Therefore, a method for 3D printing FeMnSi shape memory alloys with a wide laser energy input range is needed. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the shortcomings of the above-mentioned existing technologies and provide a method for 3D printing FeMnSi-based shape memory alloys with a wide laser energy input range. The FeMnSi-based shape memory alloy composition characterized by high Co and high Si content proposed in this method can effectively reduce the ratio of Cr equivalent to Ni equivalent, thereby eliminating the residual harmful bcc phase in the printed part even under low energy input conditions, without inhibiting the fcc-hcp phase transformation process, thereby broadening the applicable laser energy input range, significantly increasing the printing process freedom, improving print quality, and maintaining a good shape memory effect.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is: a method for 3D printing FeMnSi-based shape memory alloys with a wide laser energy input range, characterized in that the method comprises the following steps:

[0006] Step 1: Rotate and mix Fe, Mn, Co, Cr, Ni, and Si element powders at room temperature to obtain a mixed powder with high Co and high Si characteristics;

[0007] Step 2: Use metal powder bed selective laser melting 3D printing to print the mixed powder obtained in step 1 into a block to obtain a FeMnSi alloy print with significant shape memory effect.

[0008] The above-mentioned method for 3D printing FeMnSi shape memory alloy with a wide laser energy input range is characterized in that the mixed powder in step 1 is composed of the following components by mass fraction: Co 5% to 12%, Si 6% to 7%, Mn 14% to 18%, Cr 9% to 12%, Ni 4% to 6%, and the balance is Fe. The present invention adjusts the composition of the FeMnSi alloy. On the basis of the conventional alloy composition of Mn content of 14% to 18%, Cr content of 9% to 12%, Ni content of 4% to 6%, Si content of 4% to 6%, and Fe content as the balance, the Co element is added to significantly reduce the ratio of Cr equivalent to Ni equivalent, so as to eliminate the tendency of the FeMnSi alloy to preferentially form a bcc phase during cooling. The Co content is 5% to 12%. However, since Co is an fcc stabilizing element, it is not conducive to promoting the fcc-hcp phase transformation. In order to balance its influence, the method simultaneously increases the Si content to 6% to 7%. Since Si can reduce the stacking fault energy and is conducive to the fcc-hcp phase transformation, the simultaneous addition of the Co element and the increase of the Si content can eliminate the bcc harmful phase generated during the laser 3D printing process even under low energy input conditions, and ensure the significant shape memory effect of the printed part, thereby broadening the laser energy input range that can be used for printing FeMnSi shape memory alloys.

[0009] The above-mentioned method for 3D printing FeMnSi-based shape memory alloys with a wide laser energy input range is characterized by: the scanning line width in step 2 is 80μm to 100μm, the laser beam spot diameter is 80μm to 100μm, the laser power is 200W to 380W, and the scanning speed is 800mm / s to 1000mm / s. By controlling the process parameters of 3D printing, the present invention can obtain prints with excellent shape memory effects, increase printing freedom, significantly improve the printing accuracy and print quality of FeMnSi-based shape memory alloys, and maintain a good shape memory effect.

[0010] Compared with the prior art, the present invention has the following advantages:

[0011] 1. The present invention adds Co, which can significantly reduce the ratio of Cr equivalent to Ni equivalent, to eliminate the tendency of FeMnSi alloys to preferentially form bcc phases during cooling. Co content is 5% to 12%. However, since Co is an fcc-stabilizing element, it is not conducive to promoting the fcc-hcp phase transformation. To balance this effect, the Si content is simultaneously increased to 6% to 7%. Since Si can reduce the stacking fault energy and promote the fcc-hcp phase transformation, the simultaneous addition of Co and Si content can eliminate the harmful bcc phase generated during laser 3D printing, even under low energy input conditions, while ensuring a significant shape memory effect in the printed parts. This broadens the laser energy input range that can be used for printing FeMnSi shape memory alloys, significantly increasing the printing process flexibility, improving print quality, and maintaining a good shape memory effect.

[0012] 2. The present invention has no strict requirements for the energy input range of laser printing, which broadens the applicable laser energy input range. In particular, it can ensure a significant shape memory effect in printed parts under low energy input conditions. This broadens the 3D printing process window for FeMnSi-based shape memory alloys. Prints with good shape memory effects can be obtained over a wide energy range of 80μm to 100μm scanning line width, 80μm to 100μm laser beam spot diameter, 200W to 380W laser power, and 800mm / s to 1000mm / s scanning speed. This increases the printing freedom and can significantly improve the printing accuracy and quality of FeMnSi-based shape memory alloys while maintaining a good shape memory effect.

[0013] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is the fcc / bcc phase distribution diagram of the FeMnSi alloy printed part with significant shape memory effect prepared in Example 1 of the present invention.

[0015] Figure 2 This is the fcc / bcc phase distribution diagram of the FeMnSi alloy print prepared in Comparative Example 1 of the present invention.

[0016] Figure 3 This is the fcc / bcc phase distribution diagram of the FeMnSi alloy printed part with significant shape memory effect prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0017] Example 1

[0018] This embodiment includes the following steps:

[0019] Step 1: Rotate and mix Fe, Mn, Co, Cr, Ni, and Si elemental powders at room temperature to obtain a mixed powder with high Co and high Si characteristics; the mixed powder consists of the following components in mass fractions: Co 11%, Si 7%, Mn 17%, Cr 11%, Ni 6%, and the balance Fe.

[0020] Step 2: Use metal powder bed selective laser melting 3D printing with a scanning line width of 80 μm, a laser beam spot diameter of 80 μm, a laser power of 200 W, and a scanning speed of 900 mm / s to print the mixed powder obtained in step 1 into a block of 100 mm × 10 mm × 10 mm (length × width × height) to obtain a FeMnSi alloy print with significant shape memory effect.

[0021] According to calculation, the FeMnSi alloy printed parts with significant shape memory effect obtained in this embodiment are eq and Ni eq Hull calculation formula (Cr eq =Cr+0.48Si;Ni eq =Ni+0.11Mn+0.41Co), its Cr eq / Ni eq <1.5.

[0022] The FeMnSi alloy print with significant shape memory effect prepared in this embodiment was cut into a metal wire with a diameter of 1 mm for shape memory effect test (test method reference: "YS / T1307.2-2019 Nickel-Titanium Shape Memory Alloy Memory Performance Test Method Part 2: Bending Test Method") The shape memory effect is shown in Table 1. At the same time, the phase composition is tested as follows Figure 1 shown.

[0023] Table 1

[0024]

[0025] The results show that even under the condition of low energy input (laser power 200W), the bcc phase content of the printed part is very low (2.4%). Figure 1 , Figure 1The green portion represents the bcc phase, and the yellow portion represents the fcc phase. The shape recovery rate (recoverable strain / prestrain) also reaches 64%. This indicates that the use of the high-Co and high-Si content formula in step one for metal powder bed selective laser melting 3D printing significantly expands the printing process window, enabling a good shape memory effect (shape recovery rate) to be achieved even under lower laser energy input conditions. This broadens the range of usable laser energy input, which will greatly improve the printing accuracy and quality of FeMnSi-based shape memory alloy printed components with complex shapes.

[0026] Comparative Example 1

[0027] This comparative example comprises the following steps:

[0028] Step 1: Rotate and mix Fe, Mn, Cr, Ni, and Si element powders at room temperature to obtain a mixed powder having Co-free and low-Si characteristics; the mixed powder consists of the following components by mass fraction: Si 5%, Mn 17%, Cr 11%, Ni 6%, and the balance Fe.

[0029] Step 2: Use metal powder bed selective laser melting 3D printing with a scanning line width of 80 μm, a laser beam spot diameter of 80 μm, a laser power of 200 W, and a scanning speed of 900 mm / s to print the mixed powder obtained in step 1 into a block of 100 mm × 10 mm × 10 mm (length × width × height) to obtain a FeMnSi alloy print.

[0030] After calculation, the FeMnSi alloy printed parts obtained in this comparative example are eq and Ni eq Hull calculation formula (Cr eq =Cr+0.48Si;Ni eq =Ni+0.11Mn+0.41Co), its Cr eq / Ni eq >1.5.

[0031] The FeMnSi alloy print prepared in this comparative example was cut into a metal wire with a diameter of 1 mm for shape memory effect test (test method reference: "YS / T1307.2-2019 Nickel-Titanium Shape Memory Alloy Memory Performance Test Method Part 2: Bending Test Method") and its shape memory effect is shown in Table 2. At the same time, its phase composition is tested as follows Figure 2 shown.

[0032] Table 2

[0033]

[0034] The results show that the bcc phase content of the printed part is relatively high (16%) under the condition of low energy input (laser power 200W). Figure 2 , Figure 2 The green part in the middle represents the bcc phase, and the yellow part represents the fcc phase, and its shape recovery ratio (recoverable strain / pre-strain) is only 47%.

[0035] Comparing Comparative Example 1 with Example 1 reveals that the Co-free and low-Si formulation used in Comparative Example 1 exhibits a narrow printing process window for metal powder bed selective laser melting 3D printing, preventing it from achieving a good shape memory effect (shape recovery rate) at relatively low laser energy input conditions. This significantly reduces the printing precision and quality of complex FeMnSi shape memory alloy printed components. This also demonstrates that the present invention can achieve a good shape memory effect over a wide energy input range. The advantage of the present invention lies in its adaptability to a wide energy (power) input range, which the formulation in Comparative Example 1 cannot achieve.

[0036] Example 2

[0037] This embodiment includes the following steps:

[0038] Step 1: Rotate and mix Fe, Mn, Co, Cr, Ni, and Si elemental powders at room temperature to obtain a mixed powder with high Co and high Si characteristics; the mixed powder consists of the following components in mass fractions: Co 11%, Si 7%, Mn 17%, Cr 11%, Ni 6%, and the balance Fe.

[0039] Step 2: Use metal powder bed selective laser melting 3D printing with a scanning line width of 80 μm, a laser beam spot diameter of 80 μm, a laser power of 380 W, and a scanning speed of 900 mm / s to print the mixed powder obtained in step 1 into a block of 100 mm × 10 mm × 10 mm (length × width × height) to obtain a FeMnSi alloy print with significant shape memory effect.

[0040] According to calculation, the FeMnSi alloy printed parts with significant shape memory effect obtained in this embodiment are eq and Ni eq Hull calculation formula (Cr eq =Cr+0.48Si;Ni eq =Ni+0.11Mn+0.41Co), its Cr eq / Ni eq <1.5.

[0041] The FeMnSi alloy print with significant shape memory effect prepared in this embodiment was cut into a metal wire with a diameter of 1 mm for shape memory effect test (test method reference: "YS / T1307.2-2019 Nickel-Titanium Shape Memory Alloy Memory Performance Test Method Part 2: Bending Test Method") The shape memory effect is shown in Table 3. At the same time, its phase composition is tested as follows Figure 3 shown.

[0042] Table 3

[0043]

[0044] The results show that the bcc phase content of the printed part is also very low (1.4%) under the condition of higher energy input (laser power 380W). Figure 3 , Figure 3 The green portion represents the bcc phase, and the yellow portion represents the fcc phase. Their shape recovery (recoverable strain / pre-strain) also reaches 65%. This demonstrates that the high-Co and high-Si content formulation used in Step 1 for metal powder bed selective laser melting 3D printing significantly expands the printing process window, enabling a good shape memory effect (shape recovery) even at higher laser energy inputs, broadening the applicable laser energy input range. This will significantly improve the printing precision and quality of complex FeMnSi shape memory alloy printed components.

[0045] Example 3

[0046] This embodiment includes the following steps:

[0047] Step 1: Rotate and mix Fe, Mn, Co, Cr, Ni, and Si elemental powders at room temperature to obtain a mixed powder with high Co and high Si characteristics; the mixed powder is composed of the following components by mass fraction: Co 5%, Si 6%, Mn 18%, Cr 9%, Ni 4%, and the balance is Fe.

[0048] Step 2: Use metal powder bed selective laser melting 3D printing with a scanning line width of 90 μm, a laser beam spot diameter of 90 μm, a laser power of 200 W, and a scanning speed of 1000 mm / s to print the mixed powder obtained in step 1 into a block of 100 mm × 10 mm × 10 mm (length × width × height) to obtain a FeMnSi alloy print with significant shape memory effect.

[0049] According to calculation, the FeMnSi alloy printed parts with significant shape memory effect obtained in this embodiment are eq and Ni eq Hull calculation formula (Cr eq =Cr+0.48Si;Nieq =Ni+0.11Mn+0.41Co), its Cr eq / Ni eq <1.5.

[0050] The FeMnSi alloy printout with significant shape memory effect prepared in this embodiment was cut into a metal wire with a diameter of 1 mm for shape memory effect testing (test method reference: "YS / T1307.2-2019 Nickel-Titanium Shape Memory Alloy Memory Performance Test Method Part 2: Bending Test Method").

[0051] The results show that even under relatively low energy input conditions (laser power (200W)), the bcc phase content of the printed part of this embodiment is very low (2.5%), and its shape recovery rate (recoverable strain / prestrain) reaches 63%. This shows that using the high Co content and high Si content formula in step 1 for metal powder bed selective laser melting 3D printing significantly expands the printing process window, making it possible to obtain a good shape memory effect (shape recovery rate) even under relatively low laser energy input conditions, and broadening the usable laser energy input range. This will greatly improve the printing accuracy and print quality of FeMnSi-based shape memory alloy printed components with complex shapes.

[0052] Example 4

[0053] This embodiment includes the following steps:

[0054] Step 1: Rotate and mix Fe, Mn, Co, Cr, Ni, and Si elemental powders at room temperature to obtain a mixed powder with high Co and high Si characteristics; the mixed powder is composed of the following components by mass fraction: Co 5%, Si 6%, Mn 18%, Cr 9%, Ni 4%, and the balance is Fe.

[0055] Step 2: Use metal powder bed selective laser melting 3D printing with a scanning line width of 100 μm, a laser beam spot diameter of 100 μm, a laser power of 350 W, and a scanning speed of 900 mm / s to print the mixed powder obtained in step 1 into a block of 100 mm × 10 mm × 10 mm (length × width × height) to obtain a FeMnSi alloy print with significant shape memory effect.

[0056] According to calculation, the FeMnSi alloy printed parts with significant shape memory effect obtained in this embodiment are eq and Ni eq Hull calculation formula (Cr eq =Cr+0.48Si;Ni eq =Ni+0.11Mn+0.41Co), its Cr eq / Nieq <1.5.

[0057] The FeMnSi alloy printout with significant shape memory effect prepared in this embodiment was cut into a metal wire with a diameter of 1 mm for shape memory effect testing (test method reference: "YS / T1307.2-2019 Nickel-Titanium Shape Memory Alloy Memory Performance Test Method Part 2: Bending Test Method").

[0058] The results show that even under high energy input conditions (laser power (350W)), the bcc phase content of the printed part of this embodiment is very low (2.4%), and its shape recovery rate (recoverable strain / prestrain) reaches 67%. This shows that using the high Co content and high Si content formula in step 1 for metal powder bed selective laser melting 3D printing significantly expands the printing process window, making it possible to obtain a good shape memory effect (shape recovery rate) even under high laser energy input conditions, broadening the usable laser energy input range. This will greatly improve the printing accuracy and print quality of FeMnSi-based shape memory alloy printed elements with complex shapes.

[0059] Example 5

[0060] This embodiment includes the following steps:

[0061] Step 1: Rotate and mix Fe, Mn, Co, Cr, Ni, and Si elemental powders at room temperature to obtain a mixed powder with high Co and high Si characteristics; the mixed powder consists of the following components by mass fraction: Co 12%, Si 6.5%, Mn 14%, Cr 12%, Ni 5%, and the balance Fe.

[0062] Step 2: Use metal powder bed selective laser melting 3D printing with a scanning line width of 80 μm, a laser beam spot diameter of 80 μm, a laser power of 240 W, and a scanning speed of 1000 mm / s to print the mixed powder obtained in step 1 into a block of 100 mm × 10 mm × 10 mm (length × width × height) to obtain a FeMnSi alloy print with significant shape memory effect.

[0063] According to calculation, the FeMnSi alloy printed parts with significant shape memory effect obtained in this embodiment are eq and Ni eq Hull calculation formula (Cr eq =Cr+0.48Si;Ni eq =Ni+0.11Mn+0.41Co), its Cr eq / Ni eq <1.5.

[0064] The FeMnSi alloy printout with significant shape memory effect prepared in this embodiment was cut into a metal wire with a diameter of 1 mm for shape memory effect testing (test method reference: "YS / T1307.2-2019 Nickel-Titanium Shape Memory Alloy Memory Performance Test Method Part 2: Bending Test Method").

[0065] The results show that even under relatively low energy input conditions (laser power (240W)), the bcc phase content of the printed part of this embodiment is very low (1.5%), and its shape recovery rate (recoverable strain / prestrain) reaches 61%. This shows that the use of the high Co content and high Si content formula in step 1 for metal powder bed selective laser melting 3D printing significantly expands the printing process window, making it possible to obtain a good shape memory effect (shape recovery rate) even under relatively low laser energy input conditions, thereby broadening the usable laser energy input range. This will greatly improve the printing accuracy and print quality of FeMnSi-based shape memory alloy printed components with complex shapes.

[0066] Example 6

[0067] This embodiment includes the following steps:

[0068] Step 1: Rotate and mix Fe, Mn, Co, Cr, Ni, and Si elemental powders at room temperature to obtain a mixed powder with high Co and high Si characteristics; the mixed powder consists of the following components by mass fraction: Co 12%, Si 6.5%, Mn 14%, Cr 12%, Ni 5%, and the balance Fe.

[0069] Step 2: Use metal powder bed selective laser melting 3D printing with a scanning line width of 80 μm, a laser beam spot diameter of 80 μm, a laser power of 300 W, and a scanning speed of 800 mm / s to print the mixed powder obtained in step 1 into a block of 100 mm × 10 mm × 10 mm (length × width × height) to obtain a FeMnSi alloy print with significant shape memory effect.

[0070] According to calculation, the FeMnSi alloy printed parts with significant shape memory effect obtained in this embodiment are eq and Ni eq Hull calculation formula (Cr eq =Cr+0.48Si;Ni eq =Ni+0.11Mn+0.41Co), its Cr eq / Ni eq <1.5.

[0071] The FeMnSi alloy printout with significant shape memory effect prepared in this embodiment was cut into a metal wire with a diameter of 1 mm for shape memory effect testing (test method reference: "YS / T1307.2-2019 Nickel-Titanium Shape Memory Alloy Memory Performance Test Method Part 2: Bending Test Method").

[0072] The results show that even under high energy input conditions (laser power (300W)), the bcc phase content of the printed part of this embodiment is very low (1.4%), and its shape recovery rate (recoverable strain / prestrain) reaches 62%. This shows that using the high Co content and high Si content formula in step 1 for metal powder bed selective laser melting 3D printing significantly expands the printing process window, making it possible to obtain a good shape memory effect (shape recovery rate) even under high laser energy input conditions, broadening the usable laser energy input range. This will greatly improve the printing accuracy and print quality of FeMnSi-based shape memory alloy printed components with complex shapes.

[0073] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent variation made to the above embodiment based on the technical essence of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for 3D printing FeMnSi-based shape memory alloys with a wide laser energy input range, characterized in that: The method comprises the following steps: Step 1: Rotate and mix Fe, Mn, Co, Cr, Ni, and Si elemental powders at room temperature to obtain a mixed powder having high Co and high Si characteristics; the mixed powder is composed of the following components by mass fraction: Co 5% to 12%, Si 6% to 7%, Mn 14% to 18%, Cr 9% to 12%, Ni 4% to 6%, and the balance Fe; Step 2: Use metal powder bed selective laser melting 3D printing to print the mixed powder obtained in step 1 into a block to obtain a FeMnSi alloy print with significant shape memory effect; the scanning line width in the 3D printing is 80μm~100μm, the laser beam spot diameter is 80μm~100μm, the laser power is 200W~380W, and the scanning speed is 800mm / s~1000mm / s.

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