Results show that the brittle fracture is mainly caused by hydrogen brittleness that results from the oxidation arid absorbing hydrogen of copper tube during braze welding.

• 同时在加热和冷却时，由于异种材料的热胀系数差别过大，产生的较大热应力作用于已存在的裂纹，促使裂纹二次扩展，甚至使得晶粒脱落产生空洞，最终导致焊接接头漏气失效。