Cracking mechanism in laser directed energy deposition of melt growth alumina/aluminum titanate ceramics

Abstract

Thanks to its advantages of high efficiency and near-net shaping, laser directed energy deposition (LDED) is rapidly becoming a remarkable preparation technology for high-purity ceramics. However, the cracking problem in shaping process is always a great challenge for LDED to achieve industrial application. For this purpose, alumina/aluminum titanate melt-growth ceramics (A/AT MGCs) were prepared using LDED system, and the corresponding finite element thermal analysis model was developed. The solidification behavior and cracking mechanism of A/AT MGCs were investigated based on the thermal analysis model, and the influence of process parameters on the cracking characteristics was revealed with experiments. Results show that the crack morphology and distribution are controlled by microstructure and temperature gradient together. The scanning speed of 100-150 mm/min, with better microstructure and lower temperature gradient, is a preferred process window. This study provides theoretical guidance and technical support for the cracking suppression during LDED shaping of ceramics.

Advances and challenges in direct additive manufacturing of dense ceramic oxides

“…Processing parameter optimization serves as a convenient and fundamental approach to control cracks via modifying both local thermal conditions and microstructures [182]. Also, it lays the groundwork for further implementing other strategies to suppress defects, such as field-assisted dAM techniques and secondary-phase toughening [77].…”

“…Through analyzing the influence of laser power, scan speed, and scanning strategy on simulated temperature distributions, the optimal laser parameters for single-layers shaping can be determined. Huang et al [174,182] further advanced the understanding of dAM processes by developing a thermal-mechanical coupled FEM model to analyze the dynamic temperature evolution and thermal stress distribution in L-DEDed Al 2 O 3 -TiO 2 thin-walled structures (figures 17(b) and (c)). This enabled them to elucidate the crack formation mechanism in dAMed specimens, revealing a strong correlation between crack patterns, local thermal stress, and microstructure.…”

Morphology and formation mechanism of cracks in Al2O3–ZrO2 eutectic ceramics fabricated via laser powder bed fusion

“…To detect the cracks in bulks sample, the Al 2 O 3 –ZrO 2 samples were colored, penetrated, and developed with DPT‐8 colored penetrant flaw detector 33 and observed using a low‐power optical microscope. The crack density ( D ) that is defined as the ratio of the crack total length ( l ) to the cross‐sectional area ( A ) 36 were calculated under each bulk samples, through four pictures: $$$$\begin{equation}D = l{\mathrm{/}}A\end{equation}$$$$…”

Direct additive manufacturing of Al2O3–TiCp functionally graded ceramics by laser‐directed energy deposition

“…As a result of their dense internal microstructures and particle refining, shaped samples with a high melting‐cooling rate (10 3 –10 5 K/s) have outstanding properties 18 . LDED is now being widely applied and researched in the fabrication of melt‐growth ceramics 19–31 . It is feasible to integrate different materials, which greatly enhances the flexibility in material design.…”

“…18 LDED is now being widely applied and researched in the fabrication of melt-growth ceramics. [19][20][21][22][23][24][25][26][27][28][29][30][31] It is feasible to integrate different materials, which greatly enhances the flexibility in material design. This approach is not limited by the size of components, making it particularly suitable for manufacturing composites and functional graded materials.…”