The Coupling Evolution Mechanism of Microstructure and Pores during Laser Coaxial Wire Additive Manufacturing of 205C/7075 Aluminum Alloy

doi:10.3901/JME.260077

Abstract

Abstract: Laser coaxial wire additive manufacturing, with its advantages of high forming flexibility and uniform material melting, offers a novel and effective solution for the efficient forming of high-performance heterogeneous material integral structures based on 2xxx and 7xxx series aluminum alloys. To address the metallurgical porosity problem during laser coaxial wire additive manufacturing of aluminum alloys, this study combines experimental analysis with numerical simulation to investigate the differential pore distribution characteristics across different grain types and locations. It further elucidates the influence mechanisms of initial pore precipitation features and grain nucleation conditions on the competitive and cooperative evolution of microstructure and porosity. The results demonstrate that in the 205C aluminum alloy transition layer C1, the porosity at equiaxed grain boundaries (0.03%) is significantly higher than that within grains (0.01%). In the 7075 aluminum alloy transition layer C2, the porosity (1.01%) and average pore diameter (48.07 μm) in the columnar grain zone are 10.1 times and 1.68 times those in the equiaxed grain zone, respectively. During the final solidification stage, pores in the upper liquid channels of columnar grains merge with underlying pores, forming double-grain-boundary pores, while pores distant from primary dendrite tips become encapsulated by adjacent columnar grains, resulting in triple-grain-boundary interactive pores. Pores between multiple equiaxed grains exhibit near-spherical morphology due to uniform grain boundary constraints, whereas those between columnar grains adopt an elongated, intergranular distribution due to crystallographic orientation constraints. As the columnar grain growth mode transitions from convergent to parallel and finally divergent, the length, width, and roundness of intergranular pores progressively increase.

Key words: aluminum alloy, laser coaxial wire additive manufacturing, microstructure, pore, coupling evolution

CLC Number:

TG156

ZHAN Xiaohong, GAO Zhuanni, ZHANG Kaiyu, WANG Jianfeng, LI Xiang, XU Fangda. The Coupling Evolution Mechanism of Microstructure and Pores during Laser Coaxial Wire Additive Manufacturing of 205C/7075 Aluminum Alloy[J]. Journal of Mechanical Engineering, 2026, 62(3): 160-175.

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