Experimental investigation of thermite heat assisted hybrid friction stir welding of aluminium bronze alloys

Abstract

In various industrial application, the improvement in the material characteristics is required, such as high-strength, fatigue and fracture resistant welds. For the application point of view, the conventional welding involving liquid state joining of materials is not desirable because of poor weldability of materials and formation of porosity and cracking, leading to decrease in mechanical strength of the welded joint. To overcome this problem, Friction Stir Welding (FSW) is the most significant development in metal joining processes in recent era, invented by The Welding Institute (TWI) of Cambridge, England in 1991. FSW appears to offer several advantages over conventional fusion welding techniques, such as no need for expensive consumable filler materials, good mechanical and metallurgical properties of the resultant joint, absence of solidification crack, no porosity, low distortion and less energy consumption. FSW is mostly preferred as a solid-state joining process of aluminium alloys. At present, FSW is being attempted on higher-melting point materials too. But this remains a difficult task and it is quite challenging to execute the joint without any defects in case of higher-melting temperature materials. When high Strength material is Friction Stir welded, high axial load is required. This higher axial load results in installation of high capacity Friction Stir welded machines and also results in tool breakage. In addition, the higher capacity of machine for higher load and high consumption of the expensive rotating tools is also a major concern. Hence, to increase the tool life, weld efficiency and to reduce the axial load, several preheating methods or Hybrid FSW techniques have been introduced to reduce the axial load. For example, EAFSW, IAFSW, AAFSW and LAFSW. newline