Non-vacuum semi-solid mechanically assisted rotary brazing method for magnesium alloy and its composite materials

Abstract

The invention relates to a non-vacuum semi-solid machine-assisted rotary soldering method for a magnesium alloy and a composite material thereof, which comprises the following steps of: clamping the magnesium alloy and a composite material weldment thereof on a fixture, putting Zn-Sn or Zn-Al-Sn solders and the like on two surfaces to be welded, heating the weldment at the temperature of between 350 and 450 DEG C, and applying pressure of 0.1 to 1MPa to make the solder in an intermediate layer positioned in a semi-solid state; starting a rotating device, rotating at a speed of 65 to 1,500r/min for 10 to 300 seconds, and keeping the temperature constant in the rotating process; raising the temperature at a certain heating rate after rotation is stopped, and preserving heat at the predetermined temperature of between 400 and 480 DEG C for 1 to 5 minutes to make the solder dissolve parent metal with certain thickness; and applying pressure of 0.1 to 1MPa, starting the rotating device again, rotating for the second time at a speed of 65 to 600r/min for 3 to 60 seconds, stopping rotation, preserving heat for 5 to 30 minutes, and cooling with a furnace. By the method, the magnesium alloy and the composite material thereof can be efficiently and economically connected at high quality.

Description

technical field [0001] The invention relates to a welding method for magnesium alloy and aluminum matrix composite material. Background technique [0002] Magnesium alloys and their composites stand out due to their outstanding advantages such as low cost, easy preparation, good wear resistance, and strong designability in performance and function, and have become one of the mainstream studies in metal matrix composites. It has broad application prospects in parts, engine heat-resistant and wear-resistant parts, and is considered to be one of the most promising composite materials in the 21st century. However, if magnesium alloy and its composite materials are to be further popularized and applied in aerospace, weaponry and civilian products, it is necessary to solve the problem of secondary processing technology, especially the connection technology of some complex components is far behind the research of other technologies. Therefore, it is necessary to deeply study the s...

AI Technical Summary

Problems solved by technology

[0004] (1) Physical compatibility problem: Part of the solid SiC and other reinforcing phases in the liquid molten pool seriously affect the heat transfer and mass transfer process in the molten pool, making the molten pool exhibit high viscosity and poor flow. The sensitivity of defects such as fusion and incomplete penetration is high; the magnesium-based composite material and filling material in the molten pool are difficult to mix evenly, and the dilution rate is low, making it difficult to form; at the same time, the segregation of the reinforcing phase when the liquid metal solidifies destroys it. The original distribution characteristics deteriorate the performance of the joint; in addition, due to the large difference in the linear expansion coefficient between the reinforcing phase and the matrix, a large internal stress will remain in the joint during the heating and cooling process of welding, requiring further heat treatment; at the same time The melting points of the magnesium alloy matrix and the reinforcing phase (such as SiC) are very different, and the reinforcing body does not melt at the brazing temperature, resulting in poor fluidity of the solder. Due to the existence of the solid reinforcing phase, the wetting and spreading of the solder on the base metal Seriously hindered; adding some alloy elements and increasing the brazing temperature can be improved to some extent, but too high a temperature can easily cause overburning and erosion of the base metal, which brings great difficulties to the brazing process

[0005] (2) Oxide film is easy to form on the surface of magnesium alloy and its composite materials, and the melting point of MgO is very high, which seriously affects the wetting and spreading of the solder on the base metal, and becomes one of the main obstacles to the brazing of magnesium-based composite materials

In summary, this process introduces the semi-solid welding of magnesium alloys and their composites into mechanical rotation to achieve economical and efficient welding of magnesium alloys and their composites. At the same time, there is no semi-solid welding technology with the above characteristics at home and abroad. to report

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