Processability of A6061 Aluminum Alloy Using Laser Powder Bed Fusion by In Situ Synthesis of Grain Refiners

Abstract

Despite the increasing interest in laser powder bed fusion (LPBF), only a few cast aluminum alloys are available for this process. This study focuses on improving the LPBF processability of the A6061 alloy, which is challenging due to its wide solidification range, the dendritic columnar grain growth, and consequent solidification cracking. To address these issues, in situ-synthesized grain refiners can be used to induce equiaxial grain growth and prevent crack formation. A6061 RAM2 powder—a mixture of A6061, Ti, and B4C—was characterized and processed using a low-power LPBF machine to create an in situ particle-reinforced metal matrix composite. Parameter optimization was performed to evaluate the effect of their variation on the printability of the alloy. Microstructural characterization of the samples revealed that the complete reaction and the synthesis of the ceramic reinforcement did not occur. However, TiAl3 was synthesized during the process and promoted a partial grain refinement, leading to the formation of equiaxial grains and preventing the formation of solidification cracks. The tensile tests carried out on the optimized samples exhibit superior mechanical properties compared to those of A6061 processed through LPBF.

Influence of Build Orientation on Surface Roughness and Fatigue Life of the Al2024-RAM2 Alloy Produced by Laser Powder Bed Fusion (L-PBF)

“…Similar results concerning the grain refinement during additive manufacturing of high-strength Al alloys without RAM process were published in papers [31][32][33][34] in which the authors have focused their attention on the influence of the addition of nanoparticles based on elements that refine the grains and found that the resulting structure is free of cracks. On the other hand, the structure of the high-strength A6061-RAM2 alloy prepared by L-PBF was analyzed in [35], but in this case, the occurrence of microcracks was detected.…”

Strategies and Outlook on Metal Matrix Composites Produced Using Laser Powder Bed Fusion: A Review

“…Among reinforcements, compatibility between the metal alloy matrix and the reinforcements is a major consideration in material selection for achieving robust interfacial bonding within MMCs [124]. Poor compatibility between the matrices and reinforcements can lead to separation during manufacturing or deterioration in the properties (Figure 3) [125]. To achieve the desirable compatibility, wettability of reinforcements, property mismatch and chemical reaction between them should be previously understood and considered when designing MMCs.…”