铜铝钎焊接头中的金属间化合物

Intermetallic Compounds in The Copper-Aluminum Brazed Joints

摘要:

本文对近年来钎焊铜铝异种材料的相关研究进行回顾,分析了在接头形成与服役时,焊缝中金属间化合物(IMCs)的形成与生长。结果表明,金属间化合物的形成与生长在接头形成与服役过程中是不可避免的。金属间化合物的形成和生长取决于铜铝之间以及与钎料之间的原子相互扩散。金属间化合物的形核和生长必须同时满足热力学与动力学条件。脆硬性金属间化合物容易引起应力集中,且其形成与生长会加剧扩散原子的消耗,因此金属间化合物的形成与生长是导致接头缺陷(如孔洞、空洞和裂纹)的主要原因之一。当界面处金属间化合物层的厚度超过2~5μm时,接头性能会急剧下降。影响金属间化合物生长与扩散和接头缺陷的主要因素有温度,导热性,接头设计,热输入和钎料成分等。以上因素主要通过改变原子扩散过程影响金属间化合物的形成与生长。目前,控制金属间化合物形成与生长的主要方法有控制接头热输入、优化接头设计和在钎料中添加第三元素等。

Abstract:

This paper discussed the intermetallic compounds (IMCs) in the copper-aluminum brazed joints during formation and application through reviewing some recent research on brazing copper to aluminum. The review indicated that it was difficult to avoid the formation and growth of the IMCs, which depends on the mutual diffusion between Cu substrate and Al substrate as well as substrates and filler metals. Thermodynamics and kinetics are critical for the nucleation and growth of the IMCs respectively. Besides, defects (voids, cavities and cracks) in the joint mainly result from the formation and growth of the brittle IMCs because it always results in stress concentration as the source of cracks and accelerates the excessive consumption of the diffused atoms to form voids and cavities. Properties of copper-aluminum joints were severely deteriorated when the thickness of the IMCs exceeds 2~5μm. Finally, numerous factors (melting point, thermal conductivity, joint design, heat input and chemical composition) strongly impact the formation and growth of the IMCs through changing the mutual diffusion process. Moreover, these factors also have distinct effects on the defects. At present, some efficient methods used to control the IMCs in the copper-aluminum joints are heat input controlling, optimization of joint design and the addition of the third element into filler metals.