Microstructure and mechanical properties of (AlCoCrFeNi_2.1 + TiB₂) reinforced AlSi10Mg matrix composites fabricated via laser powder bed fusion

AlSi10Mg alloy is well-suited for laser powder bed fusion (LPBF) due to its excellent processability. However, its relatively low strength limits the application of this alloy in a wider range of fields. In this work, AlCoCrFeNi_2.1 high entropy alloy (HEA) was adopted as the main reinforcement for AlSi10Mg, while only a very small amount of micro-sized TiB₂ particles were introduced to improve the forming quality of the composites. With the addition of 2 wt% AlCoCrFeNi_2.1 HEA particles, corresponding to the specimen denoted as 2-A, the ultimate tensile strength (UTS) of the HEA/AlSi10Mg composite reached 506.6 MPa, but the elongation dropped to 2.53%. After adding 0.1 wt% TiB₂ particles, the (HEA + TiB₂)/AlSi10Mg composite, designated as Specimen 2-5-A, demonstrated exceptional mechanical properties with UTS of 516.9 MPa and elongation of 4.2%. As observed in the microstructure of the (HEA + TiB₂)/AlSi10Mg composite, significant refinement occurred along with partial columnar grains transforming into equiaxed grains. The enhanced strength arises from the synergistic effects of multiple strengthening mechanisms. After annealing at 300 °C for 1 h, the mechanical properties of (HEA + TiB₂)/AlSi10Mg composite were effectively tailored. The annealed composite exhibited an UTS of 410.6 MPa and an increased elongation of 8.25%, both significantly surpassing those of the matrix material. The microstructure of annealed composite indicated that the (Al-Si) eutectic network remained intact and the HEA particles still contributed to strengthening.