Thermal treatment method capable of prolonging long-time service life of welding seams in magnesium-alloy friction stir welding process

Abstract

The invention discloses a thermal treatment method capable of prolonging the long-time service life of welding seams in the magnesium-alloy friction stir welding process. The method comprises the steps that aging treatment and water quenching are conducted on a magnesium alloy subjected to solution treatment for 0.5 h to 72 h at 180 DEG C to 280 DEG C; friction stir welding is conducted at room temperature, wherein the rotating speed ranges from 100 rpm to 1,000 rpm, and the welding speed ranges from 20 mm / min to 120 mm / min; and annealing treatment is conducted on the welded magnesium alloy for 0.5 h to 10 h at 250 DEG C to 350 DEG C, the magnesium alloy is directly cooled to 100 DEG C to 200 DEG C after being annealed, and then aging treatment and water quenching are conducted for 0.5 h to 6 h. According to the thermal treatment method, a precipitated phase is introduced for the magnesium alloy, the lattice distortion degree is increased, and the crystallization rate is increased; andrare earth magnesium alloy or high-alloyed magnesium alloy which is difficult to recrystallize is rapidly crystallized in the friction stir welding process, so that the yield strength of the weldingseams is improved, and synchronous improvement of the long-time service lives in the directions parallel to or perpendicular to the welding seam direction is achieved.

Description

technical field [0001] The invention relates to a heat treatment method for improving the long-term service life of a magnesium alloy friction stir welding weld, in particular to a method for improving the recrystallization rate of a difficult-to-recrystallize magnesium alloy in the friction stir welding process by introducing precipitated phases, This results in simultaneous improvements in fatigue and creep life in both directions parallel and perpendicular to the weld seam. It belongs to the technical field of non-ferrous metal material processing. Background technique [0002] Magnesium alloys are expected to be used in large connectors for aerospace and high-speed trains due to their excellent weldability. Among them, friction stir welding has the advantages of no heating, no solder, no protective gas, energy saving and environmental protection. Therefore, magnesium alloy joints prepared by friction stir welding have broad application prospects in aerospace and transpo...

AI Technical Summary

Problems solved by technology

However, the weld strength of the rare earth magnesium alloy and high alloyed magnesium alloy prepared by friction stir welding is much lower than that of the base metal, especially in the vertical direction of the weld. Easy to crack early

This is because rare earth magnesium alloys and high-alloyed magnesium alloys contain a large number of solute atoms, which reduces the recrystallization rate of magnesium alloys during friction stir welding and reduces the recrystallization volume fraction, resulting in nuggets and The thermal-mechanical affected zone cannot be completely recrystallized, and the grains in the heat-affected zone are abnormally coarsened, which eventually leads to a decrease in the yield strength of the weld, and short fatigue and creep life

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