Copper-based brazing filler metal with gradually-changing coefficient of thermal expansion and preparing method of copper-based brazing filler metal

Abstract

The invention discloses a copper-based brazing filler metal with a gradually-changing coefficient of thermal expansion and a preparing method of the copper-based brazing filler metal. The copper-basedbrazing filler metal is prepared from metal powder, thermal expansion coefficient adjusting powder, an active agent and a dispersing agent. The preparing method of the copper-based brazing filler metal comprises the steps that the mechanical alloying metal powder and the active agent are mixed to obtain mixed powder A, the mixed powder A is equally divided into n parts, the thermal expansion coefficient adjusting powder and the dispersing agent are mixed to obtain mixed powder B, and the mixed powder B is equally divided into n(n-1) / 2 parts; the first part of the mixed powder A and 0 mixed powder B are mixed to obtain mixed powder AB1, and the nth part of the mixed powder A and the (n-1)th part of the mixed powder B are mixed to obtain mixed powder ABn; and the mixed powder AB1 is evenlyscattered into a hot-pressed sintering grinding die to obtain a first powder layer, the rest can be done in the same manner, the nth powder layer is prepared, and the n layers of powder is subjected to vacuum hot isostatic pressing to obtain a static pressed blank, multi-pass cold rolling is carried out on the static pressed blank, and the copper-based brazing filler metal is obtained. By means ofthe copper-based brazing filler metal with the gradually-changing coefficient of thermal expansion and the preparing method of the copper-based brazing filler metal, joint residual stress is reduced,the joint strength is improved, and the problem that the reliability is poor when traditional brazing filler metal and ceramic-metal are brazed is solved.

Description

technical field [0001] The invention relates to the technical field of brazing materials and brazing of dissimilar materials, in particular to a copper-based brazing filler metal with a gradient thermal expansion coefficient and a preparation method thereof. Background technique [0002] Ceramics or ceramic matrix composites have high hardness, strong wear resistance, good high-temperature mechanical properties, high-temperature oxidation resistance and thermal shock resistance, and are widely used in aerospace, automotive, and petrochemical fields. However, ceramics have poor plasticity, The high brittleness makes it difficult to process complex ceramic components. Metal materials have good toughness and machinability, but poor high temperature mechanical properties. Therefore, an effective connection method is selected to connect ceramics and metals to obtain ceramic-metal composite components, so as to combine the advantages of the two, give full play to the excellent pr...

AI Technical Summary

Problems solved by technology

For ceramic-metal brazing, commonly used solders include silver-based solders, nickel-based solders and copper-based solders, among which silver-based solders are mainly Ag-Cu-Ti solders, which have a low melting temperature, but due to silver The existence of silver-based solders results in high cost, and the silver-based solder has low strength, which is not suitable for brazing joints with strength requirements; nickel-based solders are mainly Ni-Cr, Ni-Cr-B-Si and Ni-Cr-B- Si-Mo solder has high strength, but high melting temperature and large residual stress of brazed joints; compared with nickel-based and silver-based active solder, copper-based solder has moderate melting temperature and low production cost. Good economy, but the current commercially available copper-based solder is mainly CuSnTi solder, the content of Sn element in the solder is relatively high, and the microstructure contains a large number of large block or strip-shaped SnTi compounds, which significantly increases the solder content of the solder. Brittleness, resulting in low solder strength and unstable performance; (2) Adding an intermediate slow-release layer: In order to compensate for the plastic deformation caused by the difference in thermal expansion coefficient, a single or multi-layer copper film with good plasticity is often added to the brazing joint. Strip or nickel thin strip (slow release layer), the addition method is "solder - slow release layer - solder" or "solder - slow release layer 1 - solder - slow release layer 2 - solder", however this The linear slow-release layer is not only prone to brazing defects, but also produces the interaction stress between the solder and the slow-release layer, resulting in unstable brazing performance; (3) Composite solder: composite solder is formed by adding It is prepared by adding reinforced particles with low expansion coefficient to the material. The commonly used reinforced particles are WC particles, TiN particles, SiC particles, Al 2 o 3 Particles, Cr 2 o 3 Particles, high-melting point metal elemental powder (such as Mo powder) and carbon fiber, etc., the purpose is to improve the strength of silver-based solder, and play a role in particle strengthening in silver-based solder, but the particle content should not exceed 10 vol%. The coefficient of thermal expansion of the material does not decrease significantly. At the same time, due to the poor wettability of the traditional solder to the reinforcing particles, the reinforcing particles and the solder matrix are mechanically coupled and connected, forming interface defects such as incomplete fusion and microcracks, which are not conducive to improving brazing. joint strength

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