Laser Additive Manufacturing Research Articles

Performance Improvement for the CuCrZr Alloy Produced by Laser Powder Bed Fusion Using the Remelting Process.

Owing to the high optical reflectivity of copper powder, the high-performance fabrication of copper alloys in the laser additive manufacturing (AM) field is problematic. To tackle this issue, this study employs the remelting process during laser powder bed fusion AM to fabricate defect-free and high-performance CuCrZr alloy. Compared to the non-remelting process, the remelting process yields finer grains, smaller precipitates, denser dislocations, and smaller dislocation cells. It realizes not only the dense molding of high laser reflectivity powders but also excellent mechanical properties and electrical conductivity (with an ultimate tensile strength of 329 MPa and conductivity of 96% IACS) without post-heat treatment. Furthermore, this study elucidates the influence of complex thermal gradients and multiple thermal cycles on the manufacturing process under the remelting process, as well as the internal mechanisms of microstructure evolution and performance improvement.

Recent progress in carbide‐based composite materials fabricated by laser additive manufacturing processes

AbstractFabricating and introducing new materials with new features is one of the most important goals for many scientific groups. Today, additive manufacturing (AM) is known as one of the new production methods, which can create an excellent opportunity for achieving this goal. As one of the ongoing production processes, the laser AM (LAM) methods have the proper capacity for producing new advanced materials like carbide, nitride, and boride‐based materials. Hence, this work aims to review carbide‐based materials produced by LAM techniques with the composite viewpoint. These materials can act as a matrix, reinforcement, or tertiary component in advanced composites. With this viewpoint, these composite materials were introduced in eight separate sections, which are tungsten carbide, titanium carbide, silicon carbide, niobium carbide, chrome carbide, vanadium carbide, and boron carbide, as well as high entropy alloy composites.

Effect of stress relief and solubilization heat treatments on laser additive manufactured Inconel 625: microstructure and properties

This work assesses the effect of the energy input and the stress relief and solubilization heat treatment on the microstructure and mechanical properties of an Inconel 625 alloy processed by laser additive manufacturing using directed energy deposition. Two processing conditions were used to deliver high productivity with a high energy input (HEI) and another with better geometrical precision using a lower energy input (LEI). The mechanical test samples were built vertically and horizontally aligned with the tensile test direction. The samples were submitted to residual stress relief (SR) and SR + solubilization (S) heat treatments (SR + S). Results showed increased elongation with solubilization heat treatment, while UTS and YS decreased with heat treatment combination, which was linked to the stronger texture developed in HEI condition. Samples built in the vertical direction presented lower YS. The fracture toughness of solubilization heat-treated samples showed higher values, while LEI gave just slightly higher values. Although the microstructural and mechanical features are similar between the HEI and LEI conditions, the first stands out because parts can be fabricated quickly without losing mechanical performance under quasi-static conditions, impact fracture tests, or the production of unwanted phases.

Rapid identification of highly glass-forming alloys in Cu–Zr binary system by laser glazing

The high-efficient experimental identification of novel metallic glasses with high glass-forming ability (GFA) is crucial for breaking through the traditional trial-and-error approach, which is time-consuming and costly. A rapid detection method for highly glass-forming alloys using laser glazing was introduced and validated in a classic binary Cu–Zr system with well-known GFA across a wide compositional range. The vitrification degree induced by laser glazing was assessed for each selected alloy and shows a strong correlation with GFA determined by traditional rapid solidification methods. The combination of experimental kinetic analysis and theoretical finite element simulation revealed possible thermodynamic mechanisms of glass formation and crystallization in the heat-affected zone (HAZ) formed by laser glazing. The results offer insights into not only the rapid identification method of highly glass-forming alloys using laser glazing but also the mechanism of glass formation under fast heating and cooling processes, providing guidance on the construction of bulk metallic glasses through laser additive manufacturing.

Laser additive manufacturing of hierarchical multifunctional chiral metamaterial with distinguished damage-resistance and low-frequency broadband sound-absorption capabilities

Traditional materials or advanced artificially engineered metamaterials are incapable of effectively addressing the simultaneous challenges of impact energy hazards and low-frequency noise. There is an urgent need for multifunctional materials that can address this multi-physics field coupling problem. Herein, a hierarchical multifunctional chiral metamaterial (HMCM) is proposed for damage-resistance and low-frequency broadband sound-absorption capabilities fabricated by means of laser powder bed fusion technology. Cavity resonators with internally extended tubes with hierarchical chiral configuration were selected as primary units. The damage-resistance performance of the HMCM was investigated systematically through experimental, numerical, and theoretical methods. Crashworthiness design and optimization on the multifunctional chiral metamaterial were implemented to explore the effect of geometrical parameters including distance ratio and wall thickness distribution on crushing resistance. It was determined that specific configurations in these parameters significantly enhance mechanism for dissipating energy of the HMCM. Furthermore, the designed metamaterial has been experimentally, numerically, and theoretically proven to possess quasi-perfect broadband sound absorption in the target range of 425 Hz to 553 Hz with an average sound absorption coefficient exceeding 0.9. Overall, this work not only offers a promising solution for designing multifunctional metamaterials but also highlights the potential of additive manufacturing techniques in the development of such sophisticated materials.

Ultra-strong and ductile precipitation-strengthened high entropy alloy with 0.5 % Nb addition produced by laser additive manufacturing

Achieving a superior strength-ductility combination for fcc single-phase high entropy alloys (HEAs) is challenging. The present work investigates the in-situ synthesis of Fe49.5Mn30Co10Cr10C0.5 interstitial solute-strengthened HEA containing 0.5 wt.% Nb (hereafter referred to as iHEA-Nb) using laser melting deposition (LMD), aiming at simultaneously activating multiple strengthening mechanisms. The effect of Nb addition on the microstructure evolution, mechanical properties, strengthening and deformation mechanisms of the as-deposited iHEA-Nb samples was comprehensively evaluated. Multiple levels of heterogeneity were observed in the LMD-deposited microstructure, including different grain sizes, cellular subgrain structures, various carbide precipitates, as well as elemental segregation. The incorporation of Nb atoms with a large radius leads to lattice distortion, reduces the average grain size, and increases the types and fractions of carbides, aiding in promoting solid solution strengthening, grain boundary strengthening, and precipitation strengthening. Tensile test results show that the Nb addition significantly increases the yield strength and ultimate tensile strength of the iHEA to 1140 and 1450 MPa, respectively, while maintaining the elongation over 30 %. Deformation twins were generated in the tensile deformed samples, contributing to the occurrence of twinning-induced plasticity. This outstanding combination of strength and ductility exceeds that for most additively manufactured HEAs reported to date, demonstrating that the present in situ alloying strategy could provide significant advantages for developing and tailoring microstructures and balancing the mechanical properties of HEAs while avoiding conventional complex thermomechanical treatments. In addition, single-crystal micropillar compression tests revealed that although the twining activity is reduced by the Nb addition to the iHEA, the micromechanical properties of grains with different orientations were significantly enhanced.

Multi-Objective Optimization for Forming Quality of Laser and CMT-P Arc Hybrid Additive Manufacturing Aluminum Alloy Using Response Surface Methodology

A thin-walled structure of high-strength aluminum alloy 2024 (AA2024) was fabricated using novel laser and cold metal transfer and pulse (CMT-P) arc hybrid additive manufacturing (LCAHAM) technology. The influence of the wire feeding speed, scanning speed, and laser power on the forming quality was systematically studied by the response surface methodology, probability statistical theory, and multi-objective optimization algorithm. The result showed that the forming accuracy was significantly more affected by the laser power than by the wire feeding speed and scanning speed. Specifically, there was an obvious correlation between the interaction of the laser power and wire feeding speed and the resulting formation accuracy of LCAHAM AA2024. Moreover, the laser power, wire feeding speed, and scanning speed all had noticeable effects on the spattering degree during the LCAHAM AA2024 process, with the influence of the laser power surpassing that of the other two factors. Importantly, these three factors demonstrated minimal mutual interaction on spattering. Furthermore, the scanning speed emerged as the most significant factor influencing porosity compared to the wire feeding speed and laser power. It was crucial to highlight that the combined effects of the wire feed speed and laser power played an obvious role in reducing porosity. Considering the forming accuracy, spattering degree, and porosity collectively, the recommended process parameters were as follows: a wire feeding speed ranging from 4.2 to 4.3 m/min, a scanning speed between 15 and 17 mm/s, and a laser power set at approximately 2000 W, where the forming accuracy was 84–85%, the spattering degree fell within 1.0–1.2%, and the porosity was 0.7–0.9%.

Effect of Remelting on Microstructure Formation for Multi-layer and Multi-track Laser Additive Manufacturing

Effect of Remelting on Microstructure Formation for Multi-layer and Multi-track Laser Additive Manufacturing

High-speed synchrotron x-ray imaging and multi-physics modeling of molten pool and gas dynamics in laser additive manufacturing of a medium-entropy alloy

High-speed synchrotron x-ray imaging and multi-physics modeling of molten pool and gas dynamics in laser additive manufacturing of a medium-entropy alloy

A novel laser cladding AlMgZnCuErZr alloy: Material genetic design, strengthening andtoughening mechanisms

Aluminum alloy with high strength, toughness, and corrosion resistance is one of the new materials for laser additive manufacturing of lightweight high-speed train brake discs. However, due to the non-equilibrium solidification characteristics during the laser melting process, the commercial Al alloys with high performance and laser formability face several bottlenecks in alloy composition design and preparation. This paper employs a material genetic design method to develop a novel laser cladding Al14Mg9Zn6Cu2Mn0.5Si0.6Er0.4Zr alloy, which exhibits excellent laser formability and better strength, toughness, and corrosion resistance under an optimized laser energy density of 1157 J/mm3. Specifically, an in-situ generated T-AlMgZnCuZrEr genetic phase with internal cell-like α-Al was first discovered, which significantly improves the properties of the alloy. The alloy sample demonstrates a remarkable compressive strength of 663 MPa along with a deformation of 15 %. The compressive strength and deformation product of the laser cladding sample reaches 9.9 GPa%, which is 13.44 % higher than that of the high-strength AlZnMgCu alloy prepared by other subtractive manufacturing processes. The mechanisms of matching strength-toughness and corrosion resistance of the alloy have been elucidated. This study provides a feasible material design and preparation pathway for laser additive manufacturing of high-performance and lightweight Al alloy high-speed train brake discs.

Laser additive manufacturing of Miura-origami tube inspired quasi-zero stiffness metamaterial with prominent longitudinal wave propagation

ABSTRACT Origami metamaterials have become frontiers of research in many disciplines due to their infinite design space, simple size variation, and topologically variable properties. In this study, a novel metamaterial inspired by Miura-origami tubes with a complex quasi-zero-stiffness (QZS) structure was fabricated via laser powder bed fusion (LPBF). The unit of the QZS metamaterial consists of a two-layer quadrilateral frame and two vertical springs attached to its diagonal points. The geometric accuracy, densification level and mechanical properties of the QZS parts fabricated at various processing conditions were investigated and the optimised processing parameters were determined. The displacement response of the QZS parts was analysed by experiments in conjunction with simulation analysis. The results show that the LPBF-fabricated QZS metamaterials form four extra-wide longitudinal wave band gaps under low frequencies from 660 Hz to 2500 Hz. The proposed LPBF-fabricated QZS metamaterial shows great potential in impeding the longitudinal vibration of engineering structures.

Microstructure Evolution and Frictional Wear Behavior of Al–18Si–4Mg–2Mn–0.5Fe–xCu Alloys Fabricated by Laser Additive Manufacturing

The microstructure evolution, corrosion resistance, and wear resistance of Al–18Si–4 Mg–2Mn–0.5Fe–xCu (x = 0,1,2,3,4,5 wt%) alloys prepared by laser additive manufacturing (LAM) process are studied. It is found that the addition of Cu not only produces Cu‐rich strengthened phase, but also promotes the precipitation of the second phase. With the addition of Cu, the corrosion resistance of the alloy decreases, which is due to the increase of potential difference caused by the increase of the strengthening phase. The addition of Cu can effectively inhibit corrosion cracking. The hardness and wear resistance of the alloy increase with the increase of Cu content under the synergistic strengthening of the Q‐Al5Cu2Mg8Si6 phase and Al2Cu phase. When the Cu content is 3 wt%, the hardness and wear resistance of the alloy are the best. However, with the increase of Cu content, part of the Q phase is transformed into the Al2Cu phase; this synergistic strengthening effect is weakened, and the hardness and wear resistance of the alloy are reduced, but still higher than that of the alloy without Cu addition, which indicates that the addition of Cu can effectively improve the hardness and wear resistance of the alloy.

Anisotropy in Microstructure and Mechanical Properties of Pure Zinc Fabricated by Laser Additive Manufacturing (Invited)

Anisotropy in Microstructure and Mechanical Properties of Pure Zinc Fabricated by Laser Additive Manufacturing (Invited)

Recent Progress in Laser Additive Manufacturing Using Copper‑Chromium‑ Zirconium Alloys: Formation, Microstructure, and Comprehensive Properties (Invited)

Recent Progress in Laser Additive Manufacturing Using Copper‑Chromium‑ Zirconium Alloys: Formation, Microstructure, and Comprehensive Properties (Invited)

Metallurgical Characteristics of 316L Stainless Steel by Laser Additive Manufacturing

Metallurgical Characteristics of 316L Stainless Steel by Laser Additive Manufacturing

Development of Refractory High Entropy Alloys by Laser Additive Manufacturing: Regulating Material Properties and Manufacturing Processes (Invited)

Development of Refractory High Entropy Alloys by Laser Additive Manufacturing: Regulating Material Properties and Manufacturing Processes (Invited)

Oxygen vacancy healing boosts the piezoelectricity of bone scaffolds.

Although barium titanate (BaTiO3) presented tremendous potential in achieving self-powered stimulation to accelerate bone repair, pervasive oxygen vacancies restricted the full play of its piezoelectric performance. Herein, BaTiO3-GO nanoparticles were synthesized by the in situ growth of BaTiO3 on graphene oxide (GO), and subsequently introduced into poly-L-lactic acid (PLLA) powders to prepare PLLA/BaTiO3-GO scaffolds by laser additive manufacturing. During the synthesis process, CO and C-OH in GO would respectively undergo cleavage and dehydrogenation at high temperature to form negatively charged oxygen groups, which were expected to occupy positively charged oxygen vacancies in BaTiO3 and thereby inhibit the formation of oxygen vacancies. Moreover, GO could be partially reduced to reduced graphene oxide, which could act as a conductive phase to facilitate polarization charge transfer, thus further improving the piezoelectric performance. The results showed that the oxygen peak at the specific electron binding energy in O 1s declined from 54.4% to 14.6% and the Ti3+ peak that was positively correlated with oxygen vacancies apparently weakened for BaTiO3-GO, illustrating that the introduced GO significantly decreased the oxygen vacancy. As a consequence, the piezoelectric current of PLLA/BaTiO3-GO increased from 80 to 147.3 nA compared with that of PLLA/BaTiO3. The enhanced piezoelectric current effectively accelerated cell differentiation by upregulating alkaline phosphatase expression, calcium salt deposition and calcium influx. This work provides a novel insight for the design of self-powered stimulation scaffolds for bone regeneration.

Progress of Ultra-high Temperature Oxide Ceramics: Laser Additive Manufacturing and Microstructure Evolution

Progress of Ultra-high Temperature Oxide Ceramics: Laser Additive Manufacturing and Microstructure Evolution

Exceeding the limits of conventional manufacturing by means of combining additive and subtractive material processing with cw- and ultrafast lasers

Both the ablation and drilling with ultrashort laser pulses and additive manufacturing with cw-lasers and powder bed (PBF-LB) are limited in their geometric capabilities. Drillings with ultrashort laser pulses can only achieve a limited depth for a given diameter, while limited surface qualities are achieved by the PBF-LB/M process. Therefore, a novel process has been developed which allows to exceed these limits for the first time by means of combined processing with ultrafast and cw-laser sources. The results show, that post-processing of the surfaces with ultrafast lasers increases the surface quality compared to conventional PBF-LB/M processes. The sequential ablation of local material in the previously added layer successively enables manufacturing of holes with depths that are only limited by the height of the powder bed.

Embedding of Fiber Optic Sensors in Metal Parts by Laser Welding and Additive Manufacturing: A Review

Embedding of Fiber Optic Sensors in Metal Parts by Laser Welding and Additive Manufacturing: A Review