Failure analysis on cracking of 7A09 aluminum alloy outer cylinder parts

doi:10.13251/j.issn.0254-6051.2023.05.049

Abstract

Abstract: Several 7A09 aluminum alloy outer cylinders of aircraft landing gear were found cracked during machining. The chemical composition, mechanical properties, fracture micromorphology, microstructure and microhardness of the aluminum alloy outer cylinder were analyzed to investigate the essence and causes of the cracks by means of ICP spectrometer, tensile testing machine, scanning electron microscope, optical microscope and energy dispersive spectrometer. The results show that the crack of the 7A09 aluminum alloy outer cylinder is developed from the initial crack source formed by forging at high temperature, and then the overburning microstructure along the parting surface is cracked into visible longitudinal cracks under the interaction of machining stress and thermal stress generated during the subsequent boring and heat treatment process. The main reason for the crack formation may be related to the overburning of the microstructure caused by the excessively high local temperature of the parting surface during the forging process, which belongs to the forging process defect.

Key words: 7A09 aluminum alloy, crack, failure analysis, forging process defects, overburning

CLC Number:

TG146.21

Wang Hao, Fu Neng, Feng Kangtun. Failure analysis on cracking of 7A09 aluminum alloy outer cylinder parts[J]. Heat Treatment of Metals, 2023, 48(5): 298-302.

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