A Method for Analyzing the Nucleation Mechanism of Laser Weld Microstructure

Abstract

The invention belongs to the technical field related to laser welding, and discloses a method for analyzing the microstructure nucleation mechanism of a laser welding seam. The method includes the following steps: (1) performing laser welding on sample 1, that is, test welding, and Analyze the microstructure and distribution of the laser welded seam; at the same time, TIG welding is used to perform 1 pre-welding and n-pass pre-welding on sample 2-1 and sample 2-2, respectively, and then the welds formed by pre-welding respectively Perform test welding on the above, and carry out metallographic characterization on the obtained overlapping welds; wherein, the material of sample 1, sample 2-1 and sample 2-2 are the same; n is a positive integer greater than or equal to 3; (2) Compare the number and distribution of equiaxed grains in the laser weld and overlapping weld area of ​​sample 1, and pre-identify the nucleation mechanism of the weld according to the comparison results; (3) Confirm according to the pre-identification results to analyze get the nucleation mechanism. The invention improves the accuracy and repeatability of identifying the nucleation mechanism.

Description

technical field [0001] The invention belongs to the technical field related to laser welding, and more specifically relates to a method for analyzing the microstructure nucleation mechanism of laser welding seam. Background technique [0002] The grain structure of the weld metal has a significant impact on the sensitivity to solidification cracks during welding and the mechanical properties after welding. Uniform and fine equiaxed grains can reduce the existence of solidification cracks and improve the microhardness, strength and mechanical properties of welded joints. Ductility, etc., thereby improving the performance of the welded structure. In order to control the grain size and achieve grain refinement, it is particularly important to grasp the nucleation mechanism in the material welding process. At present, it is believed that there are three main nucleation mechanisms in the molten pool: dendrite fragmentation, dendrite detachment and heterogeneous nucleation. Scho...

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Problems solved by technology

[0007] (1) The nucleation mechanism of weld microstructure can only be roughly identified, and the specific nucleation mechanism and its reasons cannot be clarified one by one and separately when multiple nucleation mechanisms coexist

[0008] (2) Mostly for TIG welding (non-melting inert gas shielded arc welding), there is no analysis of the nucleation mechanism for laser welding characteristics

[0009] (3) The same welding direction is used for pre-welding and test welding, and the two weld structures cannot be well distinguished when the welding speed is slow

[0011] (5) Only the nucleation mechanism of non-dendritic equiaxed crystals near the Al-Li alloy fusion line was analyzed, and the nucleation mechanism of equiaxed crystals in the center of the weld was not studied

[0012] (6) For EBSD (Electron Backscatter Diffraction) sample preparation of aluminum-lithium alloys, electrolytic polishing is mostly used. This method requires sub-zero temperature, which is inconvenient to operate and poor in repeatability.

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