レーザ粉末床溶融結合法により造形したMn添加Al-Cu-Mg-Zn-Si合金の硬度と微細組織に及ぼす熱処理の影響

抄録

Much attention has been paid to laser powder bed fusion (LPBF) as a manufacturing process to combine new functionalities to mechanical components since it can achieve complex shapes that cannot be processed by conventional methods. LPBF-processed aluminum alloys exhibit high strength due to their peculiar microstructure; however, LPBF parts contain substantial residual stresses, which are generally removed by annealing at the expense of strength. Therefore, there is a need to develop aluminum alloys that do not require annealing for stress relief after LPBF processing. In this study, we investigated the simultaneous achievement of strength enhancement and residual stress reduction by aging treatment on LPBF parts by adding manganese (Mn) to a high-strength aluminum alloy. Although the existence state of Mn has not been clarified, Mn delayed the loss of strength due to heat treatment by inhibiting the spheroidization of silicon-rich eutectic network and extended the time to peak aging from 8 to 24 hours at 150°C and from 1 to 8 hours at 180°C. The reduction in residual stresses ranged from 20 to 33%, depending on temperatures. Our results demonstrated the addition of Mn allows for longer times or higher temperatures on aging while increasing strength and reducing residual stress.