STUDY OF SCC AND FRACTURE TOUGHNESS BEHAVIOUR OF FSW JOINT OF MARINE ALLOY SYSTEM

Abstract

Stress corrosion cracking is a phenomenon very common in marine alloys. Most of the aluminium alloys are susceptible to stress corrosion cracking in a particular corrosive environment under tensile stresses. Cantilever beam test setup is fabricated to study the effect of stress corrosion cracking. Sample for testing is prepared according to G-58 standard. Using cantilever beam test setup SCC behaviour of FSW joint of 5086 and 2024 aluminium alloys are studied. Microscopy and SEM analysis are done on stress corroded sample to evaluate SCC. In 5086 At alloy, it is found that on increasing the value of applied load from 49.0 N to 68.6 N, time for failure of specimen decreased from 168 hr to 137 hr and average rate of deflection increased from 0.1408 mm/hr to 0.1511 mm/hr. Multiple crack opening and intergranular corrosion are the main causes of SCC failure of 5086 At alloy. In 2024 At alloy, it is found that SCC starts with pitting and intergranular attack and specimen having notch at HAZ fail earlier than specimen having notch at base metal and weld nugget. Average rate of deflection in case of 2024 At alloy tested at 49.ON is maximum for the sample having notch at HAZ. After conducting the test on Cantilever beam test setup it was found that 2024 aluminium alloy is more susceptible to SCC than 5086 aluminium alloy and material will not fail if stress intensity factor (k1) is below the threshold stress intensity factor (klscc).