Laser additive manufacturing method capable of conveniently obtaining fine equiaxed grains

Abstract

The invention discloses a laser additive manufacturing method capable of conveniently obtaining the fine equiaxed grains. The preset internal stress and distortion energy in a solidification process are regulated and controlled, a mixed structure of columnar crystals with the dislocation density larger than 10<18> m<-2>, the volume fraction ranging from 71% to 85% and the width ranging from 0.28 mm to 0.45 mm and equiaxed crystals with the volume fraction ranging from 15% to 29% and the diameter ranging from 110 [mu]m to 200 [mu]m is obtained, the columnar crystals and the equiaxed crystals are evenly distributed in a staggered mode, and the distance between the adjacent columnar crystals is 2.5 to 4.5 mm. On the basis of the sedimentary structure, triple heat treatment is accurately matched, a fine equiaxed grain structure with the volume fraction not lower than 95% and the diameter not larger than 40 [mu]m is obtained, and high-performance manufacturing of large titanium alloy components can be achieved. While fine and uniform full equiaxed crystal preparation is realized, material components are not changed, the adaptability to special-shaped complex structures is high, the additive manufacturing efficiency is not reduced obviously, and the the laser additive manufacturing method is suitable for batch industrial production.

Description

technical field [0001] The invention relates to the field of laser additive manufacturing of metal materials, in particular to a laser additive manufacturing method that can conveniently obtain fine equiaxed grains. Background technique [0002] Due to the advantages of low density, high specific strength and good corrosion resistance, titanium alloys have been widely used in the aerospace field. Laser additive manufacturing technology is an advanced manufacturing technology that uses lasers to melt and accumulate parts layer by layer based on a three-dimensional CAD model. This technology has the characteristics of high manufacturing flexibility, large size of formable components, high forming efficiency and material utilization rate, short manufacturing cycle, and no need for molds. It has great advantages in the manufacture of complex structural parts of difficult-to-machine materials such as large titanium alloys. [0003] The unique local ultrafast heating, ultrafast c...

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Problems solved by technology

[0005] The above research provides a good idea for the preparation of equiaxed grains of titanium alloys by laser additives. The addition of modified nucleating agents will change the relationship between the non-equilibrium solidification temperature gradient and solidification rate, making columnar crystals transform to equiaxed grains, but The addition of nucleating agents will change the composition of the alloy, resulting in a change in material properties and increasing potential unknown risks, which is not conducive to practical engineering applications; although the entire equiaxed grain structure can be obtained by adjusting the forming process parameters, the equiaxed grain structure is coarse and uneven in size , up to hundreds of microns, coarse Widmanstatten structure near the grain boundary, low tensile properties, which is not conducive to the improvement of comprehensive performance, and the forming process range is narrow, it is difficult to fully guarantee the consistency of product quality, which is not conducive to mass production of projects; gradually Layer-by-layer rolling can obtain fine equiaxed grain structure, but the introduction of layer-by-layer rolling will significantly reduce the efficiency of additive manufacturing, and it has poor adaptability to complex components with special shapes, making it difficult to form complex equiaxed grain structures; ultrasonic impact can also obtain relatively Fine equiaxed grain structure, but due to the ultrasonic characteristics, it will appear uneven equiaxed grain structure in the deposition direction when depositing large components, and complex components have poor adaptability, prone to uneven equiaxed grain structure, and significantly reduce additive manufacturing. efficiency

[0006] Therefore, there is an urgent need to propose a short-process method to conveniently obtain fine equiaxed grains of titanium alloys manufactured by laser additive manufacturing. While realizing the preparation of relatively fine and uniform fully equiaxed grains, it does not change the material composition, and has strong adaptability to complex structures. No significant reduction in additive manufacturing efficiency

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