Fe3Al intermetallic and 18-8 stainless steel were welded by means of tungsten inert gas (TIG) arc welding. The microstructure performance of the welding zone was analysed using a metalloscope and a scanning electron microscope. The test results indicated that microstructure of the welded metals consists of austenite, proeutectoid ferrite, acicular ferrite, carbide free bainite and lath martensite distributed on the austenitic boundaries as well as grains inside. The microhardness of the fusion zone was lower than that of Fe3Al base metal. The NiAl in the fusion zone was favourable to improve toughness and avoid the welding cracks.

The distribution of hydrogen in the welding zone of HQ130 high strength steel is calculated by using finite element method (FEM). The finite element program of hydrogen in the welding zone is worked out. In the program, the effects of welding heat input (q/v), temperature and surface-escaping coefficient of hydrogen, etc., are taken into account. Crack morphology in the fusion zone and effect of diffusion hydrogen on cracks are analyzed. Cracks originated in the partially melted zone at about 20-60m from the melting interface line and propagated parallel to the fusion zone or turned into the weld metal. Hydrogen accumulates seriously near the fusion zone, particularly at the root fusion zone. This is one of the importance reasons for the forming of cracks in this zone. The test results and analysis indicate that welding heat input should be controlled about q/v=16.0kJ/cm to prevent cracks being produced and propagated for HQ130 steel.

研究了Fe3Al/18-8异种材料扩散焊中工艺参数对界面结合、接头变形状况和剪切强度的影响。采用金相显微镜和扫描电镜（SEM）分析了不同焊接工艺条件下Fe3Al/18-8异种材料扩散焊接头的显微组织特征。结果表明合适的扩散焊工艺参数为：加热温度1020～1040℃，保温时间45～60min，焊接压力12～15MPa.

The microstructare and phase constituent near the brazing interface of a new WC-TiC-Co hard alloy was investigated by means of a scanning electron microscope, X-ray diffraction and an electron probe microanalysis. Test results indicated that the brazing joint with the interface combined excellently and can be obtained by using a Cu Zn Ni brazing filler alloy and by controlling the technology parameters. The microstrucmre of the brazing filler alloy is α+β eutectic. The brazing interface consists of WC, TiC, CuZn (α phase), and α-Co phase. There are no micro defects (such as microcracks, inclusions, etc.) near the interface.

The distribution of hydrogen in the welding zone of HQ130 high strength steel is calculated by using finite element method (FEM). The finite element program of hydrogen in the welding zone is worked out. In the program, the effects of welding heat input (q/v), temperature and surface-escaping coefficient of hydrogen, etc., are taken into account. Crack morphology in the fusion zone and effect of diffusion hydrogen on cracks are analyzed. Cracks originated in the partially melted zone at about 20-60μm from the melting interface line and propagated parallel to the fusion zone or turned into the weld metal. Hydrogen accumulates seriously near the fusion zone, particularly at the root fusion zone. This is one of the importance reasons for the forming of cracks in this zone. The test results and analysis indicate that welding heat input should be controlled about q/v=16.0kJ/cm to prevent cracks being produced and propagated for HQ130 steel.