top of page

Microstructure and Mechanical properties of Friction Stir welding on Dissimilar Inconel 600 alloy and Stainless Steel

Chin-Pao, Chenga* Yang-Sheng Youa, Chaur-Jeng Wangb, Huann-Chang Liangb, Wei-Chun Chengb

Friction stir welding (FSW) could improve the mechanical properties at the joint than conventional welding treatment does. In this study, the processes and properties of the Inconel alloy 600 that dissimilarly welding with stainless steel have been tested. We propose a double-sided FSW approach to acquire the reliable result. A most-fit stir rod was designed and a proper rotational speed with optimal feeding rate was programmed for the experiment. The specimens was analyzed for their microstructure and mechanical properties followed by the dissimilar welding 

Microstructure of double-sided FSW specimen

Tensile properties of welding specimens

When the FSW method was employed to weld Inconel 600 and stainless steel 316L, austenite grain refinement occurred in the stirring zone. In this type of material, dynamic recrystallization occurred easily during plastic deformation to cause grain refinement. Grain size reduction effectively improved mechanical properties. Accordingly, the hardness of the stirring zone and the strength and ductility of the weldments substantially increased.

of double-sided type FSW. Experimental results showed that an excellent joining effect was achieved by FSW, the microhardness of stir zone, tensile strength and elongation of FSW dissimilar joint have been improved. Furthermore. the tensile fracture site located at the stainless steel base metal, also indicating the superior joining effects by this welding approach.

Thermal Bonding of Thermoelectric Lead Telluride Materials Using New SnAg-based Solders with Titanium Doping

C. H. Cheng1, Y. S. Ke1, C. P. Cheng,*, M. J. Dai, C. K. Liu, L. L. Liao, H. H. Hsu, and R. C. Juang

Lead Telluride (PbTe) Materials owns unique thermoelectric characteristic, which has attracted considerable attention for mid-to-high temperature thermoelectric applications. The PbTe thermoelectric modules can serve as energy harvesting unit to convert heat into electricity under a high-temperature operating environment. However, the high-temperature bonding issue of PbTe module is still under investigation. This is because PbTe thermoelectric modules operated at elevated temperatures encounter the difficulty on soldering process. To address this issue, we propose a new SnAg-based solder with an additional titanium doping. Our study indicates that a well-controlled bonded interface between thermoelectric PbTe and copper (Cu) contact electrode can be reached by SnAgTi solder bonding under a process temperature of 400oC. The favorable blocking effect for ion diffusion near PbTe interface can be mainly ascribed to the use of Ni barrier and stable solder bonding property. The experimental procedure of PbTe thermoelectric module was described as follow. First, the PbTe elements through high-temperature sintering were processed by a sample preparation step including bulk cutting into 3Í3Í3 mm and surface polishing. After surface pre-treatment, a Ni barrier layer with a thickness of about 30 to 50 mm was electroplated on the PbTe element. Finally, the SnAgTi solder was used for interfacial bonding between Cu electrode and Ni barrier at a temperature of 400oC in vacuum with a pressure of 1×10-2 torr. To further investigate interface diffusion behaviors, these samples were inspected by scanning electron microscope (SEM) and electron probe X-ray microanalyzer (EPMA). From experimental results, we find that the titanium doping into SnAg solder not only can form thermally stable eutectic phase, but also enhance the interface bonding quality. The detailed material analysis and interface reaction mechanism will be provided in this work.

bottom of page