The effects of welding parameters on the weldability of different materials using brazing alloy fillers

The objectives of the study were to investigate the microwelding conditions related to diffusion mechanism and elemental migration metallurgical and microscopy investigation, and to establish the fundamental corrosion mechanism on the properties of small welding and brazing areas that consist different materials. This study focuses on the weldability of Ti/Ni using microspot brazing technology by selection of brazing condition current, 2, 2.5, 3, 3.5 and 4 kA, voltage 2 V, load 60 N and welding time 25-50 ms, this welding condition effective on brazing temperature optimization this condition. Ti and Ni were selected as base metals. Four types of metal fillers were used as filler foils, sandwiched between Ti/Ni. First type of metal fillers was, 65Ni-35Cu foil, melting point 846 degrees C; the second was, 71Ag-28Cu-1Mg foil, melting point 775 degrees C; the third was, 80Ag-18Cu-2Ti foil, melting point 782 degrees C; and fourthly was, 73Ni-18Cr-9Si foil, melting point 917 degrees C. The electrode tip face chosen was circuitous in form. All brazed joint were made by microspot brazing method. Brazing was done under normal atmospheric condition. A single lap joint was selected in order to estimation mechanical property of point by tensile shear strength test and micro hardness test. Cross-section of brazed joint was observed and analyzed by Scanning Electron Microscope and Energy Dispersible X-ray Spectroscopy, Size of nugget formed. It was found that the shear strength of brazed joints strongly depended strongly on the welding current, welding time and kind of filler. Furthermore, the fracture path and value of shear strength significantly changed with the type of filler alloy by microspot brazing and small size of nugget was obtained. Forming of several reaction layers at the interface was observed. (C) 2010 Elsevier Ltd. All rights reserved.