The fabrication of melt-growth ceramics (MGCs) via laser-directed energy deposition (LDED) is highly attractive because of its ability to directly fabricate net-shaped components in a single step, eliminating the need for molds or binders. However, the complex and rapid solidification dynamics inherent to the LDED process lead to directional microstructural growth, periodic coarse banding, and high porosity, severely limiting the components’ mechanical properties and reliability. To overcome these limitations, an innovative in situ microwave-assisted LDED process for the fabrication of Al₂O₃/YAG/ZrO₂ (AYZ) ternary eutectic ceramics was developed to allow precise control over the entire solidification and fabrication of the component. The results show that with high-adsorption microwave assistance, the global structural homogeneity of the as-fabricated samples is significantly improved, with the interlayer banded structure transitioning from an irregular morphology to a lamellar and periodic structure. Furthermore, ZrO₂ exhibits texture randomization evolution under high microwave absorption fabrication conditions. The simulation results reveal the physical mechanisms driving the material’s enhanced integrity. The microwave field suppresses the maximum thermal gradient by up to 55.3%, which homogenizes the solidification conditions. Simultaneously, it substantially prolongs the melt pool lifetime. This extended duration, combined with a critically important in situ plasma ignited by frequent collisions between laser-provided seed electrons and gas molecules, promotes dramatic densification. This dual-mechanism approach significantly reduces the internal porosity—decreasing the void fraction by 85.5% to a minimum of 0.11% and decreasing the average pore size by 49.3%. These improvements in material integrity directly translate to superior mechanical performance. While maintaining the intrinsic hardness and fracture toughness of the AYZ eutectic ceramic, the microwave-assisted process significantly reduces the anisotropy of these properties compared with those of components fabricated at room temperature. In addition, the flexural strength of the microwave-assisted sample is 22.2% greater than that of the nonmicrowave-assisted sample, reaching a maximum of 373.8 MPa, indicating synergistic control of strength and toughness. This research, therefore, establishes a novel methodology for defect mitigation and performance modulation in the laser additive manufacturing of high-quality MGCs.

The TiAl4822 (Ti-48Al-2Cr-2Nb) alloy, renowned for its exceptional high-temperature mechanical properties and low density, stands out as a highly promising candidate for critical aerospace components. However, its high chemical reactivity and inherent room-temperature brittleness pose significant challenges to the conventional manufacturing of large and complex geometries. Laser directed energy deposition (LDED), characterized by its high fabrication efficiency and remarkable process flexibility, has emerged as a crucial approach for preparing TiAl4822 alloy components. Nevertheless, the rapid melting-solidification cycle during LDED induces a substantial temperature gradient and residual stress, which results in component cracking. Currently, there is no well-established method to completely prevent crack formation. In this study, a dense and crack-free thin-walled TiAl4822 alloy component with dimensions of 30 mm×25 mm×6 mm is successfully fabricated using the whole high-temperature-assisted LDED technique. An investigation is conducted on their macro-morphology, microstructure, porosity, and microhardness. The results reveal that the thin-walled TiAl4822 alloy specimen prepared by LDED at room temperature is prone to brittle fracture primarily through cleavage, and its microstructure mainly comprises fine equiaxed grains. After implementing whole high-temperature assistance at an integral temperature of 800 ℃, the grains in the deposited layer transform from bottom to top into inclined columnar grains. The porosity is significantly reduced from 0.05% to 0.008%, accompanied by a more uniform pore-size distribution, and no macroscopic cracks are observed on the surface. Concurrently, the microhardness decreases from 390.46HV_0.2 to 354.94HV_0.2, which can be attributed to grain coarsening, a decrease in grain-boundary density, and precipitate evolution under high-temperature conditions. Overall, the integral high-temperature-assisted LDED effectively inhibits crack initiation and the formation of large pores while homogenizing the microstructure, providing a novel pathway for high-density, high-performance TiAl4822 preparing.

Laser ablation is an important process during Laser-Assisted Grinding (LAG) of hard and brittle materials. To realize controllable material removal during laser ablation of RB-SiC composites, ablation experiments under different Laser Energy Density (LAED) and LAG experiments are conducted. Evolution rules and mechanism of physical phase, ablation morphology and crack characteristics caused by laser irradiation are investigated. The forces of LAG and Conventional Grinding (CG) are compared. The results show that ablation surface changes from slight oxidation to obvious material removal with LAED increasing, and ablation depth increases gradually. The ablation products change from submicron SiO₂ particles to nanoscale particles and floccule. High LAED promotes SiC decomposition and sublimation, which leads to the increase of C element. The SiC phase forms corrugated shape in recast layer and columnar shape in Heat Affected Zone (HAZ) at 56 J/mm². The cold and heat cycle leads to formation of fishbone crack. For ablation specimen under 30 J/mm², the grinding force can be reduced by a maximum of 39% and brittle damage region is reduced. The material removal and microcrack generated will significantly reduce the hardness and improve machinability, which can promote grinding efficiency.

Melt-grown alumina-based composites are receiving increasing attention due to their potential for aerospace applications; however, the rapid preparation of high-performance components remains a challenge. Herein, a novel route for 3D printing dense (< 99.4%) high-performance melt-grown alumina-mullite/glass composites using directed laser deposition (DLD) is proposed. Key issues on the composites, including phase composition, microstructure formation/evolution, densification, and mechanical properties, are systematically investigated. The toughening and strengthening mechanisms are analyzed using classical fracture mechanics, Griffith strength theory, and solid/glass interface infiltration theory. It is demonstrated that the composites are composed of corundum, mullite, and glass, or corundum and glass. With the increase of alumina content in the initial powder, corundum grains gradually evolve from near-equiaxed dendrite to columnar dendrite and cellular structures due to the weakening of constitutional undercooling and small nucleation undercooling. The microhardness and fracture toughness are the highest at 92.5 mol% alumina, with 18.39±0.38 GPa and 3.07±0.13 MPa·m^1/2, respectively. The maximum strength is 310.1±36.5 MPa at 95 mol% alumina. Strength enhancement is attributed to the improved densification due to the trace silica doping and the relief of residual stresses. The method unravels the potential of preparing dense high-performance melt-grown alumina-based composites by the DLD technology.

Al₂O₃/Al₆Ti₂O₁₃ composite ceramics with low thermal expansion properties are promising for the rapid preparation of large-scale and complex components by directed energy deposition-laser based (DED-LB) technology. However, the wider application of DED-LB technology is limited due to the inadequate understanding of process conditions. The shaping quality, microstructure, and mechanical properties of Al₂O₃/Al₆Ti₂O₁₃ (6 mol% TiO₂) composite ceramics were systematically investigated as a function of energy input in an extensive process window. On this basis, the formation mechanism of solidification defects and the evolution process of microstructure were revealed, and the optimized process parameters were determined. Results show that high energy input improves the fluidity of the molten pool and promotes the uniform distribution and full growth of constituent phases, thus, facilitating the elimination of solidification defects, such as pores and strip gaps. In addition, the microstructure size is strongly dependent on the energy input, increasing when the energy input increases. Moreover, the morphology of the α-Al₂O₃ phase gradually transforms from cellular into cellular dendrite with increasing energy input due to changing solidification conditions. Under the comprehensive influence of solidification defects and microstructure size, the fracture toughness and flexural strength of Al₂O₃/Al₆Ti₂O₁₃ composite ceramics present a parabolic law behavior as the energy input increases. Optimal shaping quality and excellent mechanical properties are achieved at an energy input range of 0.36−0.54 W*min² g⁻¹ mm⁻¹. Within this process window, the average microhardness, fracture toughness, and flexural strength of Al₂O₃/Al₆Ti₂O₁₃ composite ceramics are up to 1640 Hv, 3.87 MPa m^1/2, and 227 MPa, respectively. This study provides practical guidance for determining the process parameters of DED-LB of melt growth Al₂O₃/Al₆Ti₂O₁₃ composite ceramics.