To study the effect of hydrogen charging on mechanical behavior of AA6061 alloy and AA6061-SS304 weld joint

Abstract

Aluminium alloy is one of the most extensively used engineering materials. It has high degree of machinability when it is compared to other lightweight materials like magnesium and titanium. Zinc, silicon, magnesium, iron, copper, tin, and manganese are frequent alloying elements. These extra elements improve the workability, electrical conductivity, corrosion resistance, and strength of aluminium. As a result hybrid structure is being preferred and replacement with lighter materials is being done. Aluminium exhibits the suitable candidate for this selection. But there is a problem of joining of Aluminium with the materials which involves numerous techniques such as riveting, nut and bolt, welding etc. In welding also there are numerous techniques as fusion welding and solid-state welding which is further classified into various other types. Now-a-days hydrogen is seen as a future fuel in vehicle. So it becomes important to store it safely since it causes hydrogen embrittlement and affects the properties of the material significantly. To overcome this, the objective is to analyse the mechanical properties of AA6061 alloy and the welding technique which was preferred for joining AA6061-SS304 was Friction Stir Welding which is a solid state welding. AA6061 alloy and AA6061-SS304 weld joint was electrochemically charged with hydrogen for various time intervals and then their microstructure, tensile test, hardness and XRD was performed to analyse the mechanical properties. By performing the above test it was found that with the increase in charging time the mechanical properties such as tensile strength and hardness was increasing but the % elongation was decreasing which indicates the brittleness nature of the material. XRD test result also suggested that for 140 hours for AA6061 there is presence of hydrogen in the form of Aluminium hydride for which the tensile strength obtained was 389.232 MPa and when compared to that of the base metal it was found to be 333.524 MPa.