Microstructure Characteristic and Its Impact on Nano-hardness of LPBF-Processed Al-based Alloy with Ti Addition

Abstract:

The influence of Ti addition into Al-based alloy fabricated by laser powder bed fusion (LPBF) technique was demonstrated. The microstructure characteristics, phase identification and nano-hardness of the LPBF-processed samples without or with 3wt% Ti addition were investigated by scanning electron microscope, electron backscatter diffraction, X-ray diffraction, transmission electron microscope and nano-indentation tests. The results reveal that a refined grain microstructure and lower average grain sizes can be obtained. Due to the heterogeneous nucleation provided by Al₃Ti precipitated phases, the ranges of grain sizes are reduced within 2.5 μm. As the low angle grain boundary increases, higher crystal lattice distortion energy contributes to the increase in average nano-hardness (to 2.36 GPa) and Young's modulus (to 92.72 GPa) values. The <100> texture of LPBF-processed Al-based alloy with 3wt% Ti addition is slightly enhanced, while there is still a random crystal orientation. The phase transformation from α-Al to Al₃Ti can be obtained.