A method for preparing a core-shell structure heterogeneous aluminum alloy rod
Core-shell structured heterogeneous aluminum alloy bars were prepared by cold metal transition welding and rotary forging deformation technology, which solved the problems of weak interface bonding and dense microstructure, and achieved a gradient combination of high strength and good plasticity, making them suitable for aerospace, automotive manufacturing and other fields.
Patent Information
- Application Number
- CN202610696100.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-05-20
- Publication Date
- 2026-07-10
AI Technical Summary
Existing technologies struggle to produce core-shell heterogeneous aluminum alloy rods with tight interfacial bonding, dense internal structure, and excellent comprehensive mechanical properties. In particular, traditional methods suffer from problems such as weak interfacial bonding, inclusion enrichment, and high costs.
A core-shell structure is formed by cold metal transition welding technology. Two aluminum alloy substrates are selected and spirally welded. Then, room temperature rotary forging plastic deformation is performed to form a gradient structure with a high-strength core and a good plastic shell. The four-hammer system of the rotary forging machine is used for high-frequency pulse load forging, and the deformation parameters are controlled to achieve interface density.
The efficient preparation of core-shell structured heterogeneous aluminum alloy rods has been achieved, with high material utilization, good interfacial bonding, and excellent comprehensive mechanical properties, making them suitable for industrial production.
Smart Images
Figure CN122352718A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of metal matrix composites, and specifically relates to a method for preparing a core-shell structured heterogeneous aluminum alloy rod. Background Technology
[0002] Aluminum alloys, with their low density, high specific strength, good corrosion resistance, and machinability, have become core structural materials in the aerospace, civil, and high-end equipment industries. The main elements contained in aluminum alloys can be divided into seven series, each with different performance characteristics. For example, 5xxx series Al-Mg alloys have excellent corrosion resistance, weldability, and plasticity, but relatively low strength, and are classified as non-heat-treatable aluminum alloys; 2xxx series Al-Cu alloys and 7xxx series Al-Zn-Mg-(Cu) alloys have higher strength but lower plasticity, and are classified as heat-treatable aluminum alloys. Although alloying strategies continuously improve the performance of aluminum alloys, the increasing types and contents of added alloying elements also bring problems such as increased stress corrosion sensitivity, decreased fracture toughness, and reduced fatigue life.
[0003] Heterogeneous materials are materials whose internal regions exhibit significant strength differences, with these regions possessing various shapes and scales ranging from micrometers to nanometers. These materials can achieve excellent plasticity while maintaining high strength, and are less dependent on the composition of the parent material, allowing for fabrication using current conventional processing techniques. However, the interface between dissimilar materials is a key factor determining their overall mechanical properties, and the stability of the interfacial bonding is a direct challenge currently facing heterogeneous materials research.
[0004] Currently, the main methods for preparing heterogeneous metallic materials include cumulative rolling, powder metallurgy, casting, and welding. Cumulative rolling is only suitable for producing plates and cannot produce shaft-like parts such as bars. Furthermore, oxides and inclusions tend to accumulate at the interlayer interfaces, leading to weak interfacial bonding. Powder metallurgy and solid-state sintering are suitable for producing precision workpieces, but powder costs are high and the preparation process is complex. Casting technology is inexpensive but prone to casting defects such as inclusions, cold shuts, and porosity. Welding is suitable for connecting large components, but intense heat input can cause instability in the heat-affected zone. Therefore, there is an urgent need to develop a new method for preparing core-shell structured heterogeneous aluminum alloy bars with tight interfacial bonding, dense internal structure, and excellent comprehensive mechanical properties. Summary of the Invention
[0005] The purpose of this invention is to provide a method for preparing a core-shell structured heterogeneous aluminum alloy rod.
[0006] The technical solution for achieving the objective of this invention is: a method for preparing a core-shell structured heterogeneous aluminum alloy rod, comprising the following steps:
[0007] Step (1): Material selection: Select two aluminum alloy substrates, one of which has higher strength and lower plasticity, and the other of which has lower strength and higher plasticity;
[0008] Step (2): Welding additive manufacturing: Through cold metal transfer welding, a substrate with low strength and high plasticity is used as a core rod, and a substrate with high strength and low plasticity is used as a welding wire. Spiral welding is performed on the surface of the core rod to form a shell, thereby obtaining a core-shell structure composite rod blank.
[0009] Step (3): Rotary forging deformation: The composite bar billet is subjected to room temperature rotary forging plastic deformation. Through multi-directional compressive stress, the core, shell and interface undergo synchronous plastic deformation to obtain a heterogeneous aluminum alloy bar with dense interface.
[0010] Furthermore, in step (2), the surface of the mandrel to be welded must be pretreated; the welding wire used for welding must be dried in an oven at 100-150℃ for 0.5-2 hours.
[0011] Furthermore, the pretreatment of the mandrel surface is as follows: use sandpaper to polish along the mandrel axis until a uniform metallic luster is achieved, and remove the surface oxide film; immerse in an 8%-10% sodium hydroxide solution for alkaline washing for 20-40 seconds, rinse with clean water, then neutralize in a 30% nitric acid solution for 1-2 minutes, and finally rinse with deionized water and dry.
[0012] Furthermore, in step (1), the substrate with lower strength and higher plasticity, i.e. the mandrel, is an Al-Mg alloy, and the substrate with higher strength and lower plasticity, i.e. the outer shell weld overlay, is an Al-Cu alloy.
[0013] Furthermore, in step (2), the cold metal transition welding adopts a pulsed composite AC mode, the shielding gas is an Ar+5%He mixed gas, and the welding wire diameter is 1.2±0.1mm; before welding, the mandrel is preheated by the welding gun running idle, and after welding, the outer diameter of the composite rod is machined to a uniform size.
[0014] Furthermore, the specific process parameters for room temperature rotary forging plastic deformation in step (3) are as follows:
[0015] The rotary forging machine is equipped with a four-hammer system to apply radial high-frequency pulse loads to the bar stock for forging.
[0016] The rotary forging mill speed is 200-400 rad / min, the feeding speed is 10-20 mm / s, the diameter reduction per pass is 0.2-0.6 mm, the hammering time is 0.002-0.005 s, the time interval between two hammerings is 0.03-0.05 s, and the temperature is controlled below 70℃ during the deformation process.
[0017] The die diameter is reduced by changing the die size step by step according to the rotary forging die size, with a cumulative equivalent variable of 0.5 to 1.5.
[0018] A core-shell structured heterogeneous aluminum alloy rod, characterized in that it is prepared by the method described above.
[0019] Compared with the prior art, the significant advantages of this invention are:
[0020] This invention enables the preparation of core-shell structured heterogeneous aluminum alloy rods. The core, made of 5356 aluminum alloy, provides high strength and work hardening capability, while the outer shell, made of 2319 aluminum alloy, provides additional strength support through precipitation strengthening. The two work together to form a gradient structure with a hard core and a soft outer shell, breaking through the traditional dilemma of strength-plasticity inversion.
[0021] This invention allows for precise control of the microstructure and mechanical properties of the core, shell, and interface regions by selecting mandrels with different compositions and welding materials, adjusting forging strain, and choosing different heat treatment process parameters according to target performance. The method is simple to operate, highly efficient, and suitable for industrial-scale production, with broad application prospects in high-end equipment fields such as aerospace and automotive manufacturing.
[0022] This invention employs cold metal transition welding technology, which falls under the category of arc additive manufacturing. Compared with traditional processes such as casting and powder metallurgy, it has advantages such as high raw material utilization, high design freedom, and high forming efficiency. Rotary forging, as an industrialized technology for intense plastic deformation, can achieve continuous production of large-size bars with a material utilization rate exceeding 90%. Attached Figure Description
[0023] Figure 1 This is a flowchart illustrating the preparation method of the core-shell structured heterogeneous aluminum alloy rod of the present invention.
[0024] Figure 2 The images shown are SEM images and EDS elemental distribution diagrams of the 5356 / 2319 interface under different forging strains in the embodiments. (a)-(d) correspond to SEM images with strains of 0, 0.5, 1.0, and 1.5, respectively, and (e)-(h) correspond to EDS elemental line scan curves. The green curve represents Mg and the blue curve represents Cu.
[0025] Figure 3 The figures shown are hardness variation diagrams of 5356 aluminum alloy and 2319 aluminum alloy under different strain in the embodiments. (a) is a microhardness distribution diagram of the core 5356 aluminum alloy under different rotary forging strain, and (b) is a microhardness distribution diagram of the outer shell 2319 aluminum alloy under different rotary forging strain. Detailed Implementation
[0026] The following describes in detail a specific embodiment of a method for preparing a core-shell structured heterogeneous aluminum alloy rod. However, it should be noted that the scope of protection of this invention is not limited by these specific embodiments, but is determined by the claims in the appendix.
[0027] The method for preparing a core-shell structured heterogeneous aluminum alloy rod according to the present invention specifically includes the following steps:
[0028] Step 1: Material Selection
[0029] Two aluminum alloys that do not undergo physical and chemical reactions are selected as the base material, with one base material having higher strength and lower plasticity, and the other base material having lower strength and higher plasticity.
[0030] Step 2: Cold metal transition welding additive manufacturing
[0031] The substrate used as the mandrel undergoes surface pretreatment, with options including mechanical grinding, alkaline washing, and acid neutralization. The mandrel is fixed on a CNC positioner, and the surface is preheated using a CMT welding torch during idle running. A dissimilar aluminum alloy welding wire is used, and spiral welding is performed in a pulsed composite AC mode, with an Ar + 5% He mixture as the shielding gas. After welding, the surface oxide scale is removed, and the material is machined to a uniform outer diameter to obtain a core-shell composite rod blank.
[0032] Step 3: Rotary forging and plastic deformation
[0033] The composite bar billet is placed in a precision rotary forging machine for room temperature rotary forging plastic deformation. The rotary forging machine is equipped with a four-hammer system. Rotary forging process parameters: rotation speed 200-400 rad / min, feed rate 10-20 mm / s, diameter reduction per pass 0.2-0.6 mm. The diameter is reduced by changing the forging die step-by-step according to the die size, with a cumulative equivalent variable of 0.5-1.5. The rotary-forged bar is then removed, surface oil is cleaned, and any poorly joined ends are cut off.
[0034] The present invention provides a core-shell structured heterogeneous aluminum alloy rod prepared using the above method, wherein the core is made of 5356 aluminum alloy and the outer shell is made of 2319 aluminum alloy.
[0035] The fabrication technology for the core-shell structure heterogeneous aluminum alloy rod includes processes such as cold metal transition welding additive manufacturing and rotary forging deformation, specifically comprising the following steps:
[0036] Step 1: Cold metal transition welding additive manufacturing
[0037] Surface pretreatment: Select a 5356 aluminum alloy rod with a diameter of 30mm and a length of 1000mm as the core rod, and perform oxide film removal treatment on its surface: use 600# sandpaper to polish along the axis of the rod until a uniform metallic luster is presented to remove the surface Al2O3 oxide film; immerse in 8%-10% sodium hydroxide solution for alkaline washing for 30 seconds, rinse with clean water, then neutralize in 30% nitric acid solution for 1 minute, and finally rinse with deionized water and dry.
[0038] Additive manufacturing: The mandrel is fixed on a CNC positioner, and the surface of the mandrel is preheated by running the CMT welding torch idle. ER2319 welding wire with a diameter of 1.2mm is selected, and the wire is pre-dried in a 120℃ oven for 1 hour. The CMT equipment uses a Fronius CMT Advanced 4000 power supply, a water-cooled welding torch, and an Ar+5%He mixed shielding gas. Helical surfacing is performed using a pulsed composite AC mode. After surfacing, the oxide scale on the surface of the surfacing layer is removed with a stainless steel wire brush, and the composite mandrel is machined to an outer diameter of 38mm using a CNC machine tool to obtain a 5356 / 2319 core-shell structure composite mandrel blank.
[0039] Step 2: Rotary forging and plastic deformation
[0040] The composite bar billet was placed in an X50 precision rotary forging mill (Xi'an Innovation Precision Instrument Research Institute) for room temperature rotary forging plastic deformation. The rotary forging mill was equipped with a four-hammer system. The rotary forging process parameters were: rotation speed 300 rad / min, feed rate 15 mm / s, diameter reduction per pass 0.4 mm, hammering time 0.0038 s, time interval between two hammering passes 0.0420 s, and deformation temperature rise controlled below 70℃. The diameter reduction was achieved by changing the die step by step according to the rotary forging die size, with cumulative equivalent variables of 0.5, 1.0, and 1.5, respectively.
[0041] Example 1
[0042] This embodiment provides a core-shell structured heterogeneous aluminum alloy rod prepared using the above method, with a core of 5356 aluminum alloy and a shell of 2319 aluminum alloy. The specific chemical composition and mass percentage of the 5356 and 2319 aluminum alloys are shown in Table 1.
[0043] Table 1: Chemical composition (wt%) of 5356 aluminum alloy and 2319 aluminum alloy in this embodiment.
[0044]
[0045] The fabrication technology for the core-shell structure heterogeneous aluminum alloy rod includes processes such as cold metal transition welding additive manufacturing and rotary forging deformation, specifically comprising the following steps:
[0046] Step 1: Cold metal transition welding additive manufacturing
[0047] Surface pretreatment: Select a 5356 aluminum alloy rod with a diameter of 30mm and a length of 1000mm as the core rod, and perform oxide film removal treatment on its surface: use 600# sandpaper to polish along the axis of the rod until a uniform metallic luster is presented to remove the surface Al2O3 oxide film; immerse in 8%-10% sodium hydroxide solution for alkaline washing for 30 seconds, rinse with clean water, then neutralize in 30% nitric acid solution for 1 minute, and finally rinse with deionized water and dry.
[0048] Additive manufacturing: The mandrel is fixed on a CNC positioner, and the surface of the mandrel is preheated by running the CMT welding torch idle. ER2319 welding wire with a diameter of 1.2mm is selected, and the wire is pre-dried in a 120℃ oven for 1 hour. The CMT equipment uses a Fronius CMT Advanced 4000 power supply, a water-cooled welding torch, and an Ar+5%He mixed shielding gas. Helical surfacing is performed using a pulsed composite AC mode. After surfacing, the oxide scale on the surface of the surfacing layer is removed with a stainless steel wire brush, and the composite mandrel is machined to an outer diameter of 38mm using a CNC machine tool to obtain a 5356 / 2319 core-shell structure composite mandrel blank.
[0049] Step 2: Rotary forging and plastic deformation
[0050] The composite bar billet was placed in an X50 precision rotary forging mill (Xi'an Innovation Precision Instrument Research Institute) for room temperature rotary forging plastic deformation. The rotary forging mill was equipped with a four-hammer system. The rotary forging process parameters were: rotation speed 300 rad / min, feed rate 15 mm / s, diameter reduction per pass 0.4 mm, hammering time 0.0038 s, time interval between two hammering passes 0.0420 s, and deformation temperature rise controlled below 70℃. The diameter reduction was achieved by changing the die step by step according to the rotary forging die size, with cumulative equivalent variables of 0.5, 1.0, and 1.5, respectively.
[0051] Testing revealed that the core-shell heterogeneous aluminum alloy rods obtained in this embodiment exhibited good interfacial bonding and no defects such as oxide enrichment. EDS analysis of the elemental distribution at the interface of the final product showed a smooth gradient transition between the Mg element on the 5356 side and the Cu element on the 2319 side, with no abrupt elemental spikes, indicating good metallurgical bonding at the interface. Further testing of the mechanical properties of the final product showed that the microhardness of the 5356 aluminum alloy core increased from an initial 82 HV to 141 HV, while the hardness of the 2319 aluminum alloy shell increased from 84 HV to 116 HV. The yield strength and tensile strength of the core reached 364 MPa and 416 MPa, respectively. This core-shell heterogeneous aluminum alloy rod achieved a gradient combination of high strength (hardness) in the core and good plasticity (softness) in the shell, resulting in excellent overall mechanical properties.
Claims
1. A method for preparing a core-shell structured heterogeneous aluminum alloy rod, characterized in that, Includes the following steps: Step (1): Material selection: Select two aluminum alloy substrates, one of which has higher strength and lower plasticity, and the other of which has lower strength and higher plasticity; Step (2): Welding additive manufacturing: Through cold metal transfer welding, a substrate with low strength and high plasticity is used as a core rod, and a substrate with high strength and low plasticity is used as a welding wire. Spiral welding is performed on the surface of the core rod to form a shell, thereby obtaining a core-shell structure composite rod blank. Step (3): Rotary forging deformation: The composite bar billet is subjected to room temperature rotary forging plastic deformation. Through multi-directional compressive stress, the core, shell and interface undergo synchronous plastic deformation to obtain a heterogeneous aluminum alloy bar with dense interface.
2. The method according to claim 1, characterized in that, In step (2), the surface of the mandrel to be welded must be pretreated; the welding wire used for welding must be dried in an oven at 100-150℃ for 0.5-2 hours.
3. The method according to claim 2, characterized in that, The pretreatment of the mandrel surface is as follows: use sandpaper to polish along the mandrel axis until a uniform metallic luster is achieved, and remove the surface oxide film; immerse in 8%-10% sodium hydroxide solution for alkaline washing for 20-40 seconds, rinse with clean water, then neutralize in 30% nitric acid solution for 1-2 minutes, and finally rinse with deionized water and dry.
4. The method according to claim 3, characterized in that, In step (1), the substrate with lower strength and higher plasticity, i.e. the mandrel, is an Al-Mg alloy, and the substrate with higher strength and lower plasticity, i.e. the outer shell weld overlay, is an Al-Cu alloy.
5. The method according to claim 4, characterized in that, In step (2), the cold metal transition welding adopts the pulsed composite AC mode, the shielding gas is Ar+5%He mixed gas, and the welding wire diameter is 1.2±0.1mm. Before welding, the mandrel is preheated by the welding gun running idle. After welding, the outer diameter of the composite rod is machined to a uniform size.
6. The method according to claim 5, characterized in that, The specific process parameters for room temperature rotary forging plastic deformation in step (3) are as follows: The rotary forging machine is equipped with a four-hammer system to apply radial high-frequency pulse loads to the bar stock for forging. The rotary forging mill speed is 200-400 rad / min, the feeding speed is 10-20 mm / s, the diameter reduction per pass is 0.2-0.6 mm, the hammering time is 0.002-0.005 s, the time interval between two hammerings is 0.03-0.05 s, and the temperature is controlled below 70℃ during the deformation process. The die diameter is reduced by changing the die size step by step according to the rotary forging die size, with a cumulative equivalent variable of 0.5 to 1.
5.
7. A core-shell structured heterogeneous aluminum alloy rod, characterized in that, Prepared using the method described in any one of claims 1-6.