Tensile fatigue fractography and microstructural analysis of al2016 and al2618 age hardened aerospace high strength aluminium alloys

Abstract

In achieving the goal of finding the optimized, suitable skin alloy material for the space shuttles under the thermal protection system, this research work has been designed and conducted. The presently used Al-Cu alloy Al2024-T3 is to be replaced due to the expected improvements and enrichment in the performance of the alloy specifically, in terms of working at extreme temperatures, stress corrosion cracking resistance, and exfoliation corrosion resistance. As the consequence of several theoretical reviews, the choosing of base materials were accomplished by considering the nose material and engine body materials of obsolete Concord flights, Al2016 and Al2618 respectively, those alloys underwent T6 and T7 aging process to obtain the four grades of Al2016-T6, Al2016-T7, Al2618-T6 and Al2618-T7. In order to reveal the physical and mechanical properties of the as prepared alloys, light microscopy test, tensile test and fatigue tests were conducted. Hence, the experimental investigation has been done on the outcomes of physical characterization, tensile performances, fatigue behaviour and post fracture analysis. Microstructural analysis, tensile tests of both longitudinal and transverse grain orientation and fatigue properties in longitudinal orientation were done by prepared the specimens based on the ASTM standards. Determination of fatigue property was done by Wohler s curve method, fatigue life prediction through Basquin Equation, estimation of fatigue strength for infinite fatigue life using Kohout-Vand#283;chet model, and tensile and fatigue fractography observations through SEM images. Appropriate results were compared with the existing skin alloy Al2024-T3. newline