4:50 PM - 5:10 PM
[14D-T20-01] In situ TEM Observation of Microstructural Evolution of Additively Manufactured Sustainable 8xxx-Series Aluminum
Keywords:In-situ heating TEM, additive manufacturing, 8xxx-series aluminum alloys
Traditionally, iron has been viewed as harmful due to its tendency to co-precipitate with other elements in 8xxx-series Al alloys. However, the importance of iron needs to be re-evaluated in the context of laser powder bed fusion (LPBF). LPBF is a process that involves rapid solidification at a rate of approximately 105 K/s. In our preliminary study, a number of AlFeMoSiZr alloys were 3D printed and analysed. These alloys exhibited the ability to maintain their hardness at approximately 400°C for up to 100 hours after tempering. The retention of hardness is a consequence of precipitation, while coarsening is hindered by the inclusion of Mo and Zr. Nonetheless, with further increases in tempering temperatures, the alloy exhibited a substantial decline in hardness. It is unknown whether this reduction in hardness stems from precipitation coarsening or the creation of new phases. In order to achieve a better comprehension, we devised a series of transmission electron microscopy (TEM) experiments on the LPBF-manufactured components. During our experiments, we captured bright field videos of the sample as the temperature increased to 250°C, 350°C, 450°C and 550°C. Each temperature was maintained for one hour. The collected images were compiled to produce an in-situ video displaying precipitation development. Furthermore, we conducted energy-dispersive X-ray spectroscopy (EDS) before and after heating to compare precipitate compositions. Furthermore, the coarsening rates were calculated and discussed at each temperature. This study on precipitation in the AlFeMoSiZr system enhances the comprehension and development of more sustainable 8xxx-series aluminium alloys, which may potentially yield improved mechanical properties.