The invention discloses a quasi-continuous laser metal 3D printing method capable of realizing regulation of nickel base alloy crystallographic texture. Laser output is set as a quasi-continuous lasermode, and then a laser metal 3D printing technical window is preliminarily optimized. The temperature field of a molten bath under the preliminarily optimized parameter is calculated by using a finite element heat transfer model; the temperature gradient G and the cooling rate xi of the moving boundary of the molten bath during closing of laser in a single pulse period are extracted, and the growth length L of a single pulse internal columnar dendrite is worked out according to a structure growth theoretical model; the laser parameter is optimized according to the matching rule that the ratioof the scanning speed V to pulse frequency f is 0.5-0.8L, and finally 3D printing forming is conducted according to the optimized parameter, so that a formed part with the consistent crystallographicorientation height is obtained. By regulating the heat source output mode, an effective remelting mechanism for mixed crystal or isometric crystal is introduced in the scanning direction, all columnar dendrite growth is obtained, and the consistency of grain orientation is remarkably improved.

Quasi-continuous laser metal 3D printing method capable of realizing regulation of nickel base alloy crystallographic texture

The invention discloses a method for achieving adjusting and controlling of titanium alloy beta crystal grains obtained through laser additional material manufacturing. The method comprises the stepsthat a laser additional material manufacturing process window is preliminarily optimized, optimized process parameters are obtained, and under the optimized process window, the temperature field of amolten pool is calculated; the temperature gradient G and the cooling rate xi of the molten pool are extracted, and the G2/xi value is worked out; the beta grain histomorphology is judged according tothe following rules, specifically, when xi is larger than or equal to 3*10 and smaller than or equal to 10 DEG C and G2/xi is smaller than or equal to 1.2*10 DEG C s/m , the beta grains are equiaxial grains, and when xi is smaller than or equal to 3*10 DEG C/s and G2/xi is larger than or equal to 3*10 DEG C s/m , the beta grains are columnar grains; the main process parameter sections of the equiaxial beta grains and the columnar beta grains are obtained; and finally, laser additional material manufacturing is conducted by adopting the corresponding process parameters, andparts controllable in beta grain histomorphology are obtained. According to the method, through molten pool temperature field simulation and solidification theory combination, achieving adjusting andcontrolling of the beta crystal grains are achieved, and the mechanical property of the formed parts can be effectively improved.

Method for achieving adjusting and controlling of titanium alloy beta crystal grains obtained through laser additional material manufacturing

The invention discloses a pulse laser surface melting method for achieving grain shape regulation of a titanium alloy surface. The method includes first preliminarily optimizing a laser surface melting process window and recording the fixed-point temperature change of the molten pool surface during the laser melting process under the optimized process window to obtain a fixed-point thermal cycle curve and the average cooling rate Xi at the molten pool center; When Xi DEG C/s and Xi/V2>=5*10 DEG Cs/m , providing continuous laser for columnar crystal with the laser power of 400-900Wand the scanning speed of 6-10mm/s; when 2*10 DEG C/s and Xi/V2 DEG Cs/m , providing pulse laser with square waveform for isometric crystal with the laser power of 600-1000W andthe scanning speed of 4-8mm/s; finally obtaining the titanium alloy surface with the beta crystal form regulated. By means of the method, regulation of the beta crystal shape on the titanium alloy surface is achieved, and the mechanical property of a formed part can be effectively improved.

Pulse laser surface melting method for achieving grain shape regulation of titanium alloy surface

The invention discloses a laser metal 3D printing method capable of achieving customization of local solidification structures of a nickel base functional part. The laser metal 3D printing method comprises the steps of drawing a correspondence relationship diagram of nickel base alloy solidification structures and solidification parameters; acquiring the solidification parameter range corresponding to a local target structure of the part according to the diagram; calculating a molten pool temperature field through a three-dimensional finite element heat transfer model, representing the solidification parameter range, and acquiring technological parameters matched with the target structure; matching all the solidification structures of the part with the technological parameters according tothe process; carrying out single-layer slicing treatment on the part, and acquiring technological parameters, changing along with positions, of a single layer till slicing and setting of technological parameters of all the layers of the part are achieved; and inputting the customized technological parameters into a 3D printing system, carrying out 3D printing, and acquiring the nickel base functional part with the customized solidification structure. According to the laser metal 3D printing method, the customized technological parameters are adopted according to the requirements of the localstructures of the part, and customization of the local solidification structures of the part can be effectively achieved.

Laser metal 3D printing method capable of achieving customization of local solidification structures of nickel base functional part

The invention belongs to the technical field of additive manufacturing and relates to a titanium alloy structural part and a laser melting deposition forming method thereof. The method includes steps:determining prone-to-crack areas of the titanium alloy structural part according to the size and structure of the titanium alloy structural part; adopting the laser melting deposition forming methodfor acquiring the titanium alloy structural part, wherein the grain morphology is controlled to be isometric crystal in forming of the prone-to-crack areas, and the grain morphology is controlled to be columnar crystal in forming of other areas. Deposited plasticity and ductility of the prone-to-crack areas are improved, serious cracking risks in a forming process of the titanium alloy structuralpart are effectively avoided and eliminated, and high forming efficiency is guaranteed. Compared with the prior art, the titanium alloy structural part and the laser melting deposition forming methodthereof have advantages that an interconnection process is avoided, special fixtures for clamping, positioning and the like are avoided, repeated machining before interconnection of small-size structures is avoided, once integral quick manufacturing of the titanium alloy structural part can be realized, and a forming period is remarkably shortened.

Titanium alloy structural part and laser melting deposition forming method thereof

The invention discloses a method for controlling brittleness Laves phases in the laser additive manufacturing process of a nickel-based high-temperature alloy. Firstly, laser additive manufacturing technological parameters are initially optimized, and a cooling medium is adopted for cooling the bottom of a base material; then a laser modulation technology is used for modulating a laser source, and superior laser modulation parameters are obtained, wherein the peak power of square waves ranges from 600 W to 1000 W, the pulse frequency of the square waves ranges from 10 HZ to 100 HZ, and the duty ratio of the square waves ranges from 0.3 to 0.6; the wave peak power of sawtooth waves ranges from 600 W to 1200 W, the wave trough power of the sawtooth waves is 0 W, and the pulse frequency of the sawtooth waves ranges from 10 HZ to 100 HZ; and according to the parameters of sine waves, the wave peak power ranges from 600 W to 1000 W, the wave trough is 0 W, and the pulse frequency ranges from 10 HZ to 100 HZ; and finally, laser additive manufacturing and forming of the nickel-based high-temperature alloy are conducted according to the above parameters, and a formed part with all small equiaxial dendritic structures and small discrete Laves phases is obtained. By means of the laser modulation method, the precipitation behavior of the Laves phases in the laser additive manufacturing process of the nickel-based high-temperature alloy can be effectively controlled, the cracking sensibility of parts obtained through laser additive manufacturing is reduced, and the microstructure is improved.

Method for controlling brittleness Laves phases in laser additive manufacturing process of nickel-based high-temperature alloy

A laser rapid preparation method of AlxCoCrFeNi high-entropy alloy comprises the steps of, weighing 1 mole of elementary substance iron powder, cobalt powder, chromium powder and nickel powder, and mechanically ball-milling the same with a plurality of moles of aluminum powder, and screening the particle sizes of the powders after ball milling; performing laser 3D printing on the screened powders,and preliminarily optimizing a process window; recording the instantaneous temperature change of the center of a molten pool in the 3D printing process by using a colorimetric pyrometer; extracting and calculating the average temperature T and the temperature fluctuation range W of the molten pool, optimizing the process parameters according to the principle that T is more than or equal to 16 Tmand less than or equal to 20 Tm and W is less than or equal to 150 degrees centigrade, wherein the obtained optimized process window has a laser output power of 800-1000W, a laser spot diameter of 15-25 mm, a defocusing amount of 2 mm, ascanning speed of 7-10 mm/s, and a powder feeding amount of 15-20 g/min The method can quickly prepare the AlxCoCrFeNi high-entropy alloy formed piece with high compactness and uniform components

Li Yantan

Papers

Method for controlling brittleness Laves phases in laser additive manufacturing process of nickel-based high-temperature alloy

Quasi-continuous laser metal 3D printing method capable of realizing regulation of nickel base alloy crystallographic texture

Pulse laser surface melting method for achieving grain shape regulation of titanium alloy surface

Laser metal 3D printing method capable of achieving customization of local solidification structures of nickel base functional part

Laser rapid preparation method of AlxCoCrFeNi high-entropy alloy