Laser Deposition Additive Manufacturing Research Articles

The preparation of gradient titanium alloy through laser deposition

Functionally gradient materials (FGMs) with continuous variation in composition or microstructure can realize gradient properties in different positions of the same component. The layer-by-layer laser deposition additive manufacturing is one of the most promising technologies that prepare FGMs with gradient properties. The present study is focused on the preparation of gradient titanium alloy by laser depositing Ti2AlNb powders on the substrate of a near-α high temperature titanium alloy. The microstructure, composition, and micro-hardness of prepared gradient titanium alloy with and without transition layer were compared and analyzed. Results show that an obvious bonding interface with variant microstructure morphology and element contents formed during directly deposited Ti2AlNb powders on near-α titanium alloy substrate and the bonding interface exhibits higher micro-hardness than the substrate and the deposited zone. However, the microstructure and the element exhibit gradient distribution characteristics along the deposition direction after adding the mixed powders of both two alloys as intermediate transition layers between the near-α titanium alloy and the Ti2AlNb alloy. The gradient distributed micro-hardness from the substrate to the top deposited zone sufficiently demonstrates the feasibility of obtaining gradient properties of gradient titanium alloy with composition transition layer during laser depositing.

Non-oxidized graphene/metal composites by laser deposition additive manufacturing

Graphene-based metallic nanocomposites are promising materials for applications where tailored strength and functionality are required such as space and automotive industries. Additive manufacturing, specifically 3D printing, is currently considered a revolutionary process to tailor and engineer materials for certain applications. Herein, we report fast and reliable approach to prepare mechanically robust, ductile and high thermally conductive graphene-based aluminum nanocomposites using laser deposition manufacturing (LDM). Conventional ball milling was used to homogenously mix graphene platelets and aluminum alloy powder (AlSi7Mg) and then sintered by LDM. Structure-property relations of aluminum/graphene nanocomposites were investigated and thus LDM process was assessed. This includes morphological characterizations such as optical microscopy, transmission electron microscopy, x-ray diffraction and energy dispersive spectrometry; and mechanical properties measurements including tensile test and Vickers hardness. The 3D printed Al-alloy/graphene nanocomposites showed increments of 60.7%, 23.03%, 193.7% and 66% in tensile strength, Young’s modulus, elongation at break and Vickers hardness in comparison with pure Al-alloy. This study proved reliability of 3D printing metallic composites with mechanical robustness and other tailored functionality such as thermal conductivity.

Direct Laser Deposition-Additive Manufacturing of Ti–15Mo Alloy: Effect of Build Orientation Induced Surface Topography on Corrosion and Bioactivity

In this study, the direct laser deposition-additive manufacturing (DLD-AM) process is employed to fabricate Ti–15Mo biomedical alloy along two build directions. The aim is to analyse the effect of induced surface topography on corrosion and in-vitro bioactivity, motivated towards ultimate reduction in post-fabrication surface modifications. The effect of surface roughness on corrosion resistance is analysed in-vitro in simulated body fluid (SBF) by electrochemical study. Owing to higher surface roughness in the vertical build samples (Ra = 52.70 ± 11.40 μm) than the horizontal build samples (Ra = 27.10 ± 4.17 μm), upto 75% higher corrosion resistance is found for horizontally built samples. The double passive barrier layer formed in horizontal build higher surface finish samples results in lower corrosion. Further, wettability test confirms that both the build orientations exhibit a hydrophilic surface nature, leading to improved cell attachment. SEM–EDS analysis establishes the in-vitro apatite formation on immersion in SBF, for both build orientation samples. This study leads to understand the role of build orientation induced surface topography for production of minimal post-surface treatment Ti–15Mo bio-implants by the DLD-AM process.

Laser deposition-additive manufacturing of ceramics/nanocrystalline intermetallics reinforced microlaminates

Laser rapid prototyping (LRP) of the Stellite12-B4C-Y2O3 mixed powders produced a bottom layer; then the Stellite12-B4C-Cu-Y2O3 mixed powders were deposited on this bottom-layer to form the microlaminates. This upper-layer showed higher wear resistance and micro-hardness than those of the bottom layer due to an action of Cu; Cu-added led lots of the AlCu2Ti intermetallics ultrafine nanocrystals (UNs) to be produced, which distributed uniformly in some location of the upper-layer matrix. UNs may destroy the atomic equilibrium state, increasing the potential/free energy and the strength/hardness of such microlaminates. The temperature of the laser induced molten pool (laser-pool) was very high, favoring the defects to be formed; UNs did not need the long waiting time to change from the normal lattice point to the interstitial particles; also the AlCu2Ti UNs had a high interface energy, which became the driving force of the atomic motions, favoring a compact fine microstructure to be formed. The AlCu2Ti UNs in laser-treated composites provides essential theoretical and experimental basis to promote the development of the laser 3D printing nano technologies.

Laser deposition-additive manufacturing of TiB-Ti composites with novel three-dimensional quasi-continuous network microstructure: Effects on strengthening and toughening

Abstract Although TiB reinforced titanium matrix (TiB-Ti) composites exhibit superior wear resistance and strength, they still demonstrate severe problems resulted from lowered toughness and ductility, as compared with titanium and its alloys. To reduce these problems, this paper tailors a three-dimensional quasi-continuous network (3DQCN) microstructure within TiB-Ti composites by in-situ laser deposition-additive manufacturing process. Results show that the laser power has great impacts on the formation of 3DQCN microstructure and the 3DQCN microstructure is beneficial to both strengthening and toughening effects on TiB-Ti composites. To have a quantitative understanding of strengthening effects, this paper, for the first time, has modeled the yield strength of TiB-Ti composites with 3DQCN microstructure.

Laser deposition-additive manufacturing of in situ TiB reinforced titanium matrix composites: TiB growth and part performance

Ceramic reinforced Ti matrix composites (TMCs) have been widely used under severe friction and heavy loading conditions due to their superior properties. Among different types of ceramic reinforcements, TiB is considered as one of the most suitable ceramic reinforcement materials for TMCs because of its high strength and stiffness, excellent interfacial bonding with Ti matrix, and low induced stress. As a laser additive manufacturing process, laser deposition-additive manufacturing (LD-AM) has been successfully utilized to fabricate Ti-based materials. However, investigations on LD-AM of in situ TiB reinforced TMCs are limited. This investigation, for the first time, reports the tomography analysis of TiB reinforcement within Ti matrix and the formation of novel flower-like microstructure. The influences of reaction energy on part performance have been explored. In addition, the effects of input fabrication variables (including laser power and Z-axis increment) on part performance (including density, microhardness, and compressive properties) have been investigated, providing guidance on selection of input fabrication variables for future research.

Development and characterization of Ti-6Al-4V to 304L stainless steel gradient components fabricated with laser deposition additive manufacturing

In this study, a multi-hopper laser deposition system is used to additively manufacture functionally graded Ti-6Al-4V to 304L stainless steel components with a vanadium interlayer. Grain morphology, phase, and composition are mapped along the component gradients with electron backscatter diffraction (EBSD) and energy dispersive X-ray spectroscopy (EDS), and mechanical property changes are assessed utilizing Vickers hardness and nanoindentation. Precipitation of brittle intermetallic compounds such as FeTi and the formation of an Fe-V-Cr sigma phase are confirmed to be the causes of mid-fabrication cracking in the components. Guided by multicomponent phase diagrams, alternate paths in composition space are proposed to strategically avoid unfavorable phase formation along the gradient. Composition-dependent adjustment of process parameters is also proposed to reduce the prevalence of observed powder inclusions, homogenize grain morphology, and improve component mechanical properties.