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.

Microstructure performance in the welding zone of T91 heat-resistan stell under the condition of TIG welding was researched by maean of metallography, X-ray diffraction and scanning electron microscope (SME). Experimental results indicated that microstructure of T91 weld metal was austenite+a little amount of 6 ferrite when using TGS-9cb filler wire. Substructure inside the austenite grain was crypto-crystal lath martensite, on which some Cr23C6 blocky carbides were distributed. The maximum hardness (HRC44) in the welding zone is near the fusion zone. There existed no obvioussoftening zone in the heat-affected zone (HAZ). For T91 Steel tube of 63mm

Microstructure at the diffusion bonding interface between Fe3Al and steel including Q235 low carbon steel and Cr18-Ni8 stainless steel was analysed and compared by means of scanning electron microscopy and transmission electron microscopy. The effect of Cr and Ni on microstructure at the Fe3Al/steel diffusion bonding interface was discussed. The experimental results indicate that it is favourable for the diffusion of Cr and Ni at the interface to accelerate combination of Fe3Al and steel during bonding. Therefore, the width of Fe3Al/Cr18-Ni8 interface transition zone is more than that of Fe3Al/Q235. And Fe3Al dislocation couples with different distances, even dislocation net occur at the Fe3Al/Cr18-Ni8 interface because of the dispersive distribution of Cr and Ni in Fe3Al phase.

The distribution of elements near the Fe3Al/Q235 diffusion bonding interface was computed by the diffusion equation as well as measured by means of EPMA. The results indicated close agreement between the two for iron and aluminium. Diffusion coefficient in the interface transition zone is larger than that in the Fe3Al and Q235 steel at the same temperature, which is favourable to elemental diffusion. The diffusion distance near the Fe3Al/Q235 interface increased with increasing heating temperature, T, and the holding time, t. The relation between the width of the interface transition zone, x, and the holding time, t, conformed to parabolic growth law: x2=4

onic microscope (TEM) and electron diffraction, etc. The test results indicated that obviously a diffusion transition zone forms near the interface of FeaAI/Q235 under the condition of heating temperature 1050～1100℃, holding time 60 rain and pressure 9.8MPa, which indicated that the diffusion interface of Fe3AI/Q235 was combined well. The diffusion transition zone consisted of Fe3AI and α-Fe(AI) solid solution. Microhardness near the diffusion transition zone was HM 480-540. There was not brittle phase of high hardness in the interface transition zone. This is favorable to enhance toughness of Fe3AI/Q235 diffusion joint.