A heat treatment method for improving the long service life of friction stir welding welds of magnesium alloys

A technology of friction stir welding and heat treatment method, applied in heat treatment furnaces, heat treatment equipment, furnaces, etc., can solve the problems of low weld strength, easy to crack in advance, unable to fully recrystallize, etc., to solve the problem of coarse grain damage fatigue life and The effect of fine grain loss on creep life, increase in recrystallization nucleation particles, and avoid abnormal grain growth

Inactive Publication Date: 2021-02-26
CENT SOUTH UNIV
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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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  • A heat treatment method for improving the long service life of friction stir welding welds of magnesium alloys
  • A heat treatment method for improving the long service life of friction stir welding welds of magnesium alloys
  • A heat treatment method for improving the long service life of friction stir welding welds of magnesium alloys

Examples

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Effect test

Embodiment 1

[0024] In this example, the raw material is GW123 magnesium alloy. After solid solution treatment, aging treatment and water quenching are carried out at 200°C for 60 hours, and friction stir welding is carried out at room temperature with a rotation speed of 200rpm and a welding speed of 20mm / min. Magnesium alloys were annealed at 300°C for 3 hours, and after annealing, the temperature was directly lowered to 150°C for 6 hours of aging treatment and water quenching; fatigue and creep life tests were performed on the obtained magnesium alloy welds along the parallel and perpendicular directions of the welds. , where the fatigue life test temperature is 150°C and the load is 120MPa, the creep life test temperature is 250°C and the load is 120MPa; as a comparison, the GW123 magnesium alloy weld without heat treatment and directly subjected to friction stir welding is also under the same conditions Fatigue and creep life tests were performed in parallel and perpendicular to the we...

Embodiment 2

[0029] In this example, the raw material is WE43 magnesium alloy. After solution treatment, aging treatment and water quenching are carried out at 180°C for 72 hours, and friction stir welding is carried out at room temperature. The rotating speed is 1000rpm and the welding speed is 100mm / min. Magnesium alloys were annealed at 250°C for 3 hours, and after annealing, the temperature was directly lowered to 100°C for 6 hours of aging treatment and water quenching; fatigue and creep life tests were carried out on the obtained magnesium alloy welds along the parallel and perpendicular directions of the welds. , where the fatigue life test temperature is room temperature and the load is 100MPa, the creep life test temperature is 200°C and the load is 150MPa; as a comparison, the WE43 magnesium alloy weld without heat treatment and directly subjected to friction stir welding is also under the same conditions Perform fatigue and creep life tests parallel and perpendicular to the weld ...

Embodiment 3

[0034] In this example, the raw material is AZ80 magnesium alloy. After solution treatment, aging treatment and water quenching are carried out at 280°C for 0.5h, and friction stir welding is carried out at room temperature with a rotation speed of 800rpm and a welding speed of 120mm / min. The magnesium alloy was annealed at 350°C for 0.5h, and after annealing, the temperature was directly lowered to 200°C for 0.5h aging treatment and water quenching; the obtained magnesium alloy welds were subjected to fatigue and creep along the parallel and perpendicular weld directions. Variable life test, in which, the fatigue life test temperature is 200 ℃, the load is 60MPa, the creep life test temperature is 300 ℃, the load is 60MPa; as a comparison, the AZ80 magnesium alloy weld without heat treatment and directly subjected to friction stir welding is also Fatigue and creep life tests were performed in parallel and perpendicular to the weld direction under the same conditions. The test...

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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...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C21D9/50C22F1/06
CPCC21D9/50C22F1/002C22F1/06
Inventor 霍庆欢张至柔杨续跃杨昭
Owner CENT SOUTH UNIV
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