High strength Al-Cu-Mg based alloy with synchronous improved tensile properties and hot-cracking resistance suitable for laser powder bed fusion

In present work, a novel crack-free Al-Cu-Mg-Si-Ti alloy with synchronous improved tensile properties and hot-cracking resistance was proposed and successfully manufactured by laser powder bed fusion (LPBF). The microstructure evolution behaviors and the corresponding strengthening mechanisms were investigated in detail. The LPBF-processed Al-Cu-Mg-Si-Ti alloy presents a heterogeneous microstructure consisting of ultrafine equiaxed grains (UFGs) at the boundary and coarse columnar grains (CGs) at the center of the single molten pool. Pre-precipitated D0 22-Al3Ti particles were found to act as the nuclei to refine the grains at the boundary of the molten pool during solidification process, which is attributed to the low cooling rate providing the sufficient incubation time for the precipitation of D022-Al3Ti. There are two orientation relationships (ORs) between alpha-Al and D022-Al3Ti, i.e. [0 01]alpha-Al//[0 01]D022-Al3Ti, (20 0)alpha-Al//(20 0)D022-Al3Ti and [1 1 over bar 2 over bar ]alpha-Al//[ 1 over bar 11 ]D022-Al3Ti, (1 1 over bar 1)alpha-Al//( 1 over bar 1 2 over bar )D022-Al3Ti , which are two of the eight ORs predicted with the E2EM model. Refined grains in present alloy, no matter for UFGs or CG, exhibited high critical hot-cracking stress, which means a strong hot-cracking resistance. Dual-nanoprecipitation of Cu-, Mg-, and Si-rich Q' and S' phases was introduced to enhance the mechanical performance of alpha-Al matrix. The as-built sample exhibits superior tensile properties, with the yield strength (YS) of 473 +/- 8 MPa, ultimate tensile strength (UTS) of 541 +/- 2 MPa and elongation (EI) of 10.9% +/- 1.2%. (c) 2022 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

This study proposes and successfully manufactures a novel crack-free Al-Cu-Mg-Si-Ti alloy with improved tensile properties and hot-cracking resistance using laser powder bed fusion (LPBF). The microstructure evolution and strengthening mechanisms are investigated, revealing that pre-precipitated D0 22-Al3Ti particles act as nuclei to refine the grains, leading to strong hot-cracking resistance. Dual-nanoprecipitation of Cu-, Mg-, and Si-rich phases is introduced to enhance the mechanical performance of the alloy.