采用扫描电镜(SEM)、能谱分析(EDS)、X射线衍射(XRD)和电子探针(EPMA)对Fe3Al/Q235扩散焊界面的析出相形貌进行观察和成分测定，研究微观析出相的形成以及工艺参数(T, t , p)的影响. 结果表明， Fe3Al/Q235扩散焊界面靠近Fe3Al一侧形成FeAl(Cr)析出相，是引起扩散焊接头脆性断裂的关键. 扩散焊温度T、保温时间t与析出相区宽度y符合抛物线规律: y2=3.5 (t-t0)exp[-5.6×104/(RT)]. 在降低加热温度和保温时间的条件下，增加焊接压力可促进Fe3Al/Q235界面原子的扩散，避免脆性析出相的形成，保证Fe3Al/Q235扩散焊接头的性能.
Morphology, structure and chemical composition of the precipitate at Fe3Al/Q235 diffusion-bonded interface were studied by means of scanning electron microscope (SEM), energy dispersive spectrum (EDS), X-ray diffractometer (XRD) and electron probe micro-analysis (EPMA). The formation of the precipitate and the effect of technological parameters on the precipitate were also investigated. The results indicate that FeAl(Cr) was formed in the Fe3Al side of the Fe3Al/Q235 diffusion-bonded interface, which is the key to cause brittle fracture of the Fe3Al/Q235 bonded joint. The relation between the formation and growth of FeAl(Cr) and bonding parameters obeys the parabolic law, y2=3.5 (t-t0）exp[-5.6 ×10 4/(RT)]. So in order to avoid the formation of the precipitate and to ensure the performance of the Fe3Al/Q235 bonded joint, it is necessary to increase pressure for accelerating the atom diffusion at the interface with lower heating temperature and shorter bonding time.
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