A method for refining titanium alloy grains by additive manufacturing

Abstract

The invention discloses a method for refining titanium alloy grains manufactured by additive manufacturing, which belongs to the field of additive manufacturing. The method includes: placing the titanium alloy substrate in an atmosphere protection box of an additive manufacturing device; controlling the hydrogen concentration and ambient pressure in the atmosphere protection box to facilitate the hydrogen absorption of the titanium alloy; adjusting the temperature of the titanium alloy substrate to a temperature favorable for the hydrogen absorption of the titanium alloy; The additive manufacturing system in the additive manufacturing device is used. After several layers are deposited continuously, an external force volume deformation system is introduced to dehydrogenate the deposited layer by external force, and the temperature of the titanium alloy substrate is controlled to be unfavorable for the hydrogen absorption temperature of the titanium alloy, and the temperature control is repeated. , Depositing until a predetermined deposition form is obtained. The method is based on the principle of titanium alloy absorbing hydrogen and applying external force to prevent the formation of titanium alloy columnar crystals and achieve the purpose of grain refinement. This method has the characteristics of further grain refinement, high efficiency and easy implementation.

Description

technical field [0001] The invention relates to 3D printing, in particular to a method for thinning and additively manufacturing titanium alloy grains, which belongs to the field of additive manufacturing. Background technique [0002] Laser additive manufacturing technology was developed in the 1980s. It combines laser additive manufacturing technology with the rapid prototyping principle of rapid prototyping technology to form a new rapid manufacturing technology. First, the solid model of the part is formed in the computer through 3D CAD software, and then the model established by CAD is layered according to a certain thickness, and then the 3D solid model is converted into a 2D outline model, and then under the control of the machine tool or robot , using methods such as synchronous powder feeding laser deposition to fill a given shape point by point with metal materials in a certain path until a three-dimensional solid shape is formed. [0003] It can be known from the...

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Problems solved by technology

[0005] In this method, due to the limitation of the power of the ultrasonic equipment, during the solidification process of the deposited metal, due to the low fluidity of the molten metal and rapid solidification, the ultrasonic wave cannot produce cavitation inside the molten metal, and cannot produce sufficient nucleation. On the other hand, due to the upward transmission of ultrasonic waves from the workbench, the ability of the deposited layer to receive ultrasonic waves is different at different heights, and the ability to control columnar crystals is limited.

[0006] 2. The electromagnetic stirring method, similar to the ultrasonic vibration method, suppresses the formation and growth of columnar crystals through the action of external force stirring the molten pool. Limited ability to improve organizational performance

[0007] 3. Heat treatment method, which is a common method for processing titanium alloys. However, during laser additive manufacturing, especially in the process of manufacturing large and thick parts, due to the extremely high energy density in the manufacturing process, extremely strong heat is generated inside the parts. The internal stress causes cracks on the surface of the part to cause the part to fail. This is a problem that needs to be solved before heat treatment. Stress relief annealing may cause the part to crack and fail directly. Therefore, when manufacturing large parts, the method of changing the structure and properties of heat treatment is not applicable.

However, due to the extremely high yield strength of titanium alloys, the external force deformation often uses heavy pressure and high impact to deform the forming layer, so the external force deformation system is usually very large, and the existing external force deformation system only improves the grain size of the surface layer of the part. However, it cannot achieve the improvement of the overall performance of alloy parts

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