Filling composite welding flux vibrating liquid phase welding method for non-continuous strengthening aluminium base composite material

Abstract

A liquid-phase vibration welding method by filling composite flux for noncontinuously reinforced Al-base composition includes such steps as abrading two surface to be welded, ultrasonic washing in acetone, drying in the air, fixing by fixture in opposite mode, filling composite flux between two surfaces, heating to smelt the flux, vibrating while pressing, and cooling.

Description

(1) Technical field [0001] The invention relates to a welding method, in particular to a welding method for aluminum-based composite materials. (2) Background technology [0002] Discontinuously reinforced aluminum matrix composites are composed of a matrix metal aluminum alloy with good plasticity and toughness and some non-metallic short fibers, whiskers or particles with high strength, high modulus, high melting point, low density and low thermal expansion coefficient, such as commonly used Al 2 o 3 Short fibers, SiC, AlBO whiskers and Al 2 o 3 , SiC, TiC particles, etc., compounded by a special preparation process. It is the special composite structure of this material that makes it have more excellent comprehensive properties than the original aluminum alloy matrix, such as specific strength, high specific stiffness, good wear resistance, small thermal expansion coefficient, etc., so in the fields of aerospace and national defense, Such as missiles, tanks, armored ...

AI Technical Summary

Problems solved by technology

However, this has the potential to compromise the matrix strength, resulting in a loss of strength in the composite

Some scholars also use high-energy laser beams, combined with nitrogen sieve cooling and temperature field adjustment, to induce and improve the interface reaction between the reinforcement phase and the matrix of aluminum matrix composites to a certain extent, thereby increasing the joint strength, but the problem has not been completely solved.

In addition, the fusion welding process is limited to aluminum-based composite materials with a low volume fraction of the reinforcement phase (<20%), and for composite materials with a higher volume fraction (such as composite materials for electronic packaging devices, the volume fraction of reinforcement phase is generally greater than 30%). is helpless

[0008] 2. Friction welding

[0013] (2) In the absence of an intermediate layer, there is a phenomenon of direct contact between the reinforcement phase and the reinforcement phase on the contact surface of the aluminum matrix composite material, and it is difficult to realize the diffusion connection between the reinforcement phases under the diffusion welding condition

[0018] While instantaneous liquid phase welding has more advantages, it also has some disadvantages: (1) Due to the static isothermal solidification, the segregation of the reinforcing phase caused by the solid-liquid interface during the solidification process of the liquid eutectic region becomes the TLP welding of this material. the main problem

However, the thickness of the intermediate layer selected by this method is generally around a few microns, which requires high roughness of the surface to be welded, especially for components with a large welding area, it is difficult to realize, so the engineering significance is not ideal

In addition, when the particle size contained in the composite material is large, the degree of particle segregation can also be reduced. However, from the perspective of composite material performance, the preparation of composite materials generally pursues micron, submicron or even nanoscale particles as the reinforcing phase (2 ) The instantaneous liquid phase welding temperature generally exceeds 550°C. At this temperature, the base metal will soften to varying degrees, which is a challenge for the composite material matrix

(3) Instantaneous liquid phase welding is mostly carried out in a vacuum environment, which limits the shape and size of the components to be welded and reduces the adaptability of this method

[0022] (2) Improper control of the welding process will lead to the melting of the matrix, and the enhanced phase segregation in the diffusion zone; no enhanced phase layer remains in the brazing seam structure, which cannot maintain the original special structure and special properties of the base metal

This is not suitable for occasions with special performance requirements for joints, such as joints that need to maintain good anti-damping characteristics and dimensional stability, etc.

[0023] (3) The melting points of the aluminum alloy matrix and the reinforcement phase are very different. At the brazing temperature, the matrix part melts, but the reinforcement does not melt, resulting in stickiness of the brazing filler metal, poor fluidity, and wetting of the brazing filler metal on the base metal. Spreading is seriously hindered by the presence of solid reinforcement phase, adding some alloying elements and increasing the brazing temperature can be improved to some extent, but the temperature is too high and it is easy to cause overburning and erosion of the base metal, which brings a negative impact on the brazing process. come very difficult

However, for discontinuous fiber-reinforced aluminum matrix composites, there are challenges, mainly due to the serious reinforcement phase segregation in the nugget.

In addition, the existence of the reinforcing phase in the aluminum matrix composite complicates the distribution of the current lines and the distribution of the electrode pressure, which brings difficulties to the selection of welding parameters and the control of welding quality.

Moreover, the resistance of the reinforcement of the composite material is very different from that of the matrix. During the resistance welding process, the composite material is likely to be over-melted, spattered, the fibers are bonded, broken and voids are generated, and the strength of the joint is greatly affected.

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