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Abstract Post-weld heat-treatment (PWHT) of dissimilar AA7475-AA2198 friction stir welds (FSW) at 560 °C followed by water-quenching since cracks were observed at the TMAZ/SZ interface in retreating AA7475 upon quenching. Microstructural… Click to show full abstract
Abstract Post-weld heat-treatment (PWHT) of dissimilar AA7475-AA2198 friction stir welds (FSW) at 560 °C followed by water-quenching since cracks were observed at the TMAZ/SZ interface in retreating AA7475 upon quenching. Microstructural studies revealed that composition difference at high-temperature solution-treatment was the driving force for Cu diffusion from advancing AA2198 through grain boundary liquid-metal thin-films, and caused intergranular segregation of a sufficient amount of Cu-Zn phase. Weld residual stresses, weak interfacial strength, grain boundary transition (premelting), and wetting along with thermal expansion coefficient discrepancies were found to be the associated phenomena in intergranular failure.
Journal Title: Materials Letters
Year Published: 2020
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