Melt Flow Behavior Research Articles

Influence of layer thickness and heat treatment on microstructure and properties of selective laser melted maraging stainless steel

As one of the main parameters of selective laser melting (SLM) process, layer thickness has a significant impact on the forming performance and efficiency of printed parts. Based on microstructure analysis and properties testing, the metallurgical mechanism, phase composition and mechanical behavior of SLM-formed Corrax stainless steel with different layer thicknesses were discussed. The influence of heat treatment process on the properties was comparatively investigated. The results indicated that at smaller or larger layer thicknesses, the increase in melt dynamic instability and spheroidisation feature easily induced the formation of unfused pore defects, which in turn led to lower relative density and mechanical properties. At the appropriate layer thickness, the suitable melt flow behaviour promoted the formation of good metallurgical bonding between adjacent melt channels. The maximum tensile strength, yield strength and hardness of the samples prepared at a layer thickness of 60 μm were 1224 MPa, 948 MPa and 39.2 HRC, respectively. The microstructure of the as-built samples was martensite and a small amount of austenite. With increasing layer thickness, the cooling rate of the molten pool decreased and the austenite content increased. After solution treatment, the alloying elements dissolved in the martensitic matrix resulted in lower mechanical properties. After aging and solution aging treatment, the mechanical properties were significantly improved due to precipitation strengthening of NiAl nanoparticles and dislocation strengthening. The corresponding tensile strengths were 1655 MPa and 1796 MPa, the yield strengths were 1328 MPa and 1573 MPa, and the hardnesses were 45.7 HRC and 50.2 HRC, respectively.

Coupling effect of dynamic power and oscillation path on butt weld formation and melt flow behavior during aluminum alloys

The influence of the coupling effect between dynamic power and oscillation path on the formation of weld seams and the fluid behavior of the molten pool during laser welding of 5A06 aluminum alloy was investigated through numerical simulation and experimentation. Three power modes were compared in the experiments: equal power (EP), delayed dynamic power (D-DP), and non-delayed dynamic power (ND-DP). The experimental results show that both D-DP and ND-DP modes are favorable to improve the mechanical properties. Among them, the joints formed under the D-DP mode exhibit the best mechanical properties, with an average tensile strength reaching ≈ 99.1% of the base material, which is an increase of ≈ 35.3% and ≈ 5.6% compared to the EP and ND-DP modes, respectively. Numerical simulation results indicate that the D-DP mode effectively mitigates the average flow velocity of the molten pool, reduces the collision effects between liquid flows, suppresses the impact of fluid on the keyhole walls, and improves the stability of the keyhole and the welding process, thereby enhancing the mechanical properties of the joints.

Investigations of Melt Flow Behavior of Aluminium Metal Particle-Reinforced HDPE Composites

Investigations of Melt Flow Behavior of Aluminium Metal Particle-Reinforced HDPE Composites

Application of Numerical Modeling and Finite Element Analysis in Fused Filament Fabrication: A Review.

Additive manufacturing (AM) is not necessarily a new process but an advanced method for manufacturing complex three-dimensional (3D) parts. Among the several advantages of AM are the affordable cost, capability of building objects with complex structures for small-batch production, and raw material versatility. There are several sub-categories of AM, among which is fused filament fabrication (FFF), also commonly known as fused deposition modeling (FDM). FFF has been one of the most widely used additive manufacturing techniques due to its cost-efficiency, simplicity, and widespread availability. The FFF process is mainly used to create 3D parts made of thermoplastic polymers, and complex physical phenomena such as melt flow, heat transfer, solidification, crystallization, etc. are involved in the FFF process. Different techniques have been developed and employed to analyze these phenomena, including experimental, analytical, numerical, and finite element analysis (FEA). This study specifically aims to provide a comprehensive review of the developed numerical models and simulation tools used to analyze melt flow behavior, heat transfer, crystallization and solidification kinetics, structural analysis, and the material characterization of polymeric components in the FFF process. The strengths and weaknesses of these numerical models are discussed, simplifications and assumptions are highlighted, and an outlook on future work in the numerical modeling and FE simulation of FFF is provided.

The surface morphologies and internal pores evolution of a CuSn10 alloy fabricated by laser powder bed fusion

The fabrication of high quality copper alloys using laser powder bed fusion (LPBF) technology remains challenging due to their low laser absorption and high thermal conductivity. LPBF often involves intrinsic defects, such as rough surface and internal pores, which largely deteriorate the performance of as-built copper alloy components. Here we studied the effect of scanning speed on the evolution of surface morphologies and internal pores of LPBF-fabricated CuSn10 alloy. The melt flow behaviors were studied by both experiments and in situ observations where combined a high-speed camera with an infrared thermal imager. With increasing the scanning speed, the morphology of melt track evolves from a continuous track to a discontinuous one, whereas the internal defects change from a great number of spherical pores to many irregular pores. A higher scanning speed decreases the peak temperature of the melt pool and causes less overlaps between neighboring melt tracks, thus deteriorating wetting behaviors. It is expected that the obtained results are beneficial for guiding the additive manufacturing of copper alloy parts with high metallurgical quality and thus promoting their industrial applications.

Dynamic evolution of temperature field, flow field, and solidification behavior during multilayer multitrack laser cladding

During multilayer multitrack laser cladding, secondary melting and solidification in the interlayer lap zone have a significant impact on the mechanical properties of cladding coatings. However, mathematical modeling of the melt flow and solidification behavior of multilayer, multitrack laser cladding interlayer lap zones is lacking. In this paper, a 3D finite element model was established to investigate the mass and heat transfer processes in both lap and non-lap zones during the laser cladding of multilayer multitrack Fe-Cr-based alloys on 45# steel surface. A dynamic grid is used to track the free surface of the melt pool, while the enthalpy method is used to simulate the solid-liquid phase transition. The change in thermophysical properties with temperature, as well as the change in laser energy and alloy powder flow density in the lap zone, were taken into consideration. The influence of the number of cladding layers on the heat and mass transfer in the molten pool, remelting, and solidification in the lap zone was investigated, along with its intrinsic mechanism. The results show that the model can accurately predict the size and microstructural change law of coating layers, including the grain size of the lap region between layers. The melt pool temperature and grain size increase with the number of cladding layers, while the convection and cooling velocities decrease. In addition, the grain size in the lap zone of the cladding is larger than that in the nearby non-lap zone. Using solidification parameters extracted from the solidification front of the molten pool, changes in grain size and morphology were predicted for both the interlayer lap and non-lap zones. The numerical calculation results were consistent with the experimental measurements.

Predicting maximum strain hardening factor in elongational flow of branched pom-pom polymers from polymer architecture

We present a model-driven predictive scheme for the uniaxial extensional viscosity and strain hardening of branched polymer melts, specifically for the pom-pom architecture, using the small amplitude oscillatory shear mastercurve and the polymer architecture. A pom-pom shaped polymer is the simplest architecture with at least two branching points, needed to induce strain hardening. It consists of two stars, each with q\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$q$$\\end{document} arms of the molecular weight Mw,a\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${M}_{w,a}$$\\end{document}, connected by a backbone of Mw,b\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${M}_{w,b}$$\\end{document}. Despite the pom-pom constitutive model, experimental data of systematic investigations lack due to synthetic complexity. With an optimized approach, we synthesized polystyrene pom-pom model systems with systematically varied Mw,a\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${M}_{w,a}$$\\end{document} and Mw,b\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${M}_{w,b}$$\\end{document}. Experimentally, we identify four characteristic strain rate dependent regimes of the extensional viscosity, which can be predicted from the rheological mastercurve. Furthermore, we find that the industrially important maximum strain hardening factor depends only on the arm number by [q2/ln(3q)]\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$[{q}^{2}/{{{{{\\mathrm{ln}}}}}}({\\sqrt{3}}q)]$$\\end{document}. This framework offers a model-based design of branched polymers with predictable melt flow behavior.

Numerical and experimental analysis of 3D printer hot ends

The design of the hot end plays a critical role in additive manufacturing, especially in material extrusion. Yet the melt flow behavior within the hot end assembly has not been explicitly presented regarding the hot end design. The present study intends to fill this knowledge gap by employing a two-phase approach to investigate the melt dynamics through three commercially available hot ends. The hot ends considered are E3D v6 Standard, v6 Gold, and Revo Six, which were chosen based on brand, design, and functionality. In Phase 1, an experimental apparatus was developed to assess the impact of feeding rate and extrusion temperature on the outlet temperature, outlet velocity, and under-extrusion percentage of extruded polymer. In Phase 2, the polymer flow through each hot end is explored utilizing a computational fluid dynamics model, which was validated using data obtained in Phase 1. It was determined that the filament feeding rate is the most influential parameter in polymer extrusion and that Revo Six’s symmetrical design affects the stability of extrusion. It was also revealed that the thermal evolution of the melted filament within the hot end assembly is directly affected by the length of the heating region and the polymer's material properties. The experimental and numerical procedures developed in this investigation can be useful to 3D printing users and manufacturers in selecting a hot end assembly based on application requirements.

Performance evaluation of biodegradable polymer PHBV and PBAT blends with adjustable melt flow behaviour, heat deflection temperature, and morphological transition

AbstractMelt blending is a reliable and well‐demonstrated strategy for improving the mechanical, thermal, rheological, and surface properties of biopolymers. Poly(hydroxy‐3‐butyrate‐co‐3‐hydroxyvalerate) (PHBV) and poly(butylene adipate‐co‐terephthalate) (PBAT) are the two popular choices for blending polymers due to their diverse properties and complementary soil biodegradable behaviour. Due to their immiscibility, however, blending with the help of processing additives is necessary to reap the most significant benefits from this process and to avoid immiscibility issues. This study utilized the additives (peroxides and epoxy‐based chain extender) to compatibilize the biodegradable polymers PHBV and PBAT in a 60:40 blending ratio. The tensile strength and Young's modulus of the PHBV/PBAT(60/40) blend were improved by 32% and 64%, respectively, after adding a combination of peroxide (0.02 phr) and chain extender (0.3 phr) due to the formation of a complex network structure with increased chain length. The positive effect of an additive addition was also reflected by a 30°C increment in heat deflection temperature of biodegradable blend due to its high modulus value as supported by mechanical properties. The combined action of a peroxide and chain extender demonstrated a significantly higher complex viscosity of the PHBV/PBAT(60/40) blend due to the formation of a crosslinked polymer network as analyzed by rheological analysis. Our research demonstrated the effect of additives and their combined impact on analytical properties of PHBV/PBAT(60/40) blend to guide future work in improving their candidature to serve as a drop‐in solution in replacing non‐biodegradable petro‐based plastic products.

An investigation of novel biodegradable flexible copolyester derived from bio-based isosorbide: Synthesis and characterization of poly(butylene-co-isosorbide sebacate)

A series of fully bio-based poly(butylene-co-isosorbide sebacate) (PBISe) copolyesters are synthesized from sebacic acid (Se), 1,4-butanediol (BDO), and isosorbide (IS) via a two-step melt polycondensation method. The synthesized PBISe copolyesters are characterized using various techniques, including 1H NMR spectroscopy; GPC; FT-IR spectroscopy; HR-XRD; DSC; TGA; transparency, tensile, and tear strength testing; and rheological property analysis. The Mw and Mn values of the PBISe copolyesters are 126,000–148,000 and 50,000–63,500, respectively. The introduction of the rigid, bulky, and asymmetric IS unit disrupts the regularity and mobility of the polymer chain, resulting in a nearly linear reduction of the melting temperature, enthalpy, and crystallinity, from 66 to 42 °C, 81 to 37 J/g, and 41.4 to 19.0%, respectively, with an increase in the IS content from 0 to 30 mol% relative to the total diol concentration. The reduction of crystallinity without the formation of new crystal planes with the poly(butylene sebacate (PBSe) copolyester containing 30 mol% IS resulted in improved transparency (73.8% transmittance at 600 nm). Additionally, the PBISe copolyesters exhibit Tonset and Tmax in excess of 405 °C and 425 °C, respectively, as well as shear-thinning and viscous melt-flow behaviors, making them suitable for melt processing. The tensile strength and elongation at break of the hot-pressed films of the IS-added PBISe copolyesters with ≤16% content are 31.6–36.3 MPa and 639.2–809.9%, respectively. The developed PBISe copolyesters have great potential as bio-based, biodegradable, and flexible materials for packaging and coating applications with low processing temperatures.

Numerical modelling of the viscoelastic polymer melt flow in material extrusion additive manufacturing

ABSTRACT In material extrusion (MEX), it is challenging to accurately predict the steady and transient feeding forces at various polymer extrusion rates when printing island and thin-walled structures involving rapid start/stop or acceleration/deceleration, especially for semi-crystalline polymers. This research presents a non-isothermal viscoelastic Computational Fluid Dynamics model to investigate the steady and transient feeding forces, as well as the phase transition process and viscoelastic behaviour of polylactic acid (PLA), a semi-crystalline polymer, during the extrusion process. The study establishes a relationship between polymer flow and viscoelastic stress, demonstrating that the elastic effect during extrusion is more significant than the viscous effect, particularly at higher feeding rates. Furthermore, the study uncovers critical aspects of PLA melt flow behaviour during the MEX process, laying the foundation for future research and optimisation of MEX printing processes.

Improved formation accuracy and mechanical properties of laser-arc hybrid additive manufactured aluminum alloy through beam oscillation

High-frequency circular beam oscillation was employed for the laser-arc hybrid additive manufacturing of AA4047 aluminum alloy. Under the optimized oscillating frequency of 300 Hz, the effects of oscillating diameter (D) on the forming accuracy, microstructure and mechanical properties of deposited thin-walls were studied. It was found that the effective forming width reached a maximum of 88.9 %, and the porosity decreased from 0.1 % to 0.01 % when the D increased from 0 to 1.2 mm. Furthermore, the machining allowance was reduced from 1.51 to 1.25 mm, which indicated that the formation accuracy was improved by 17 %. The increasing D reduced the average size of grains from 55.9 to 44.8 μm, showing a refinement degree of 19.9 %. These improvements reduced the microhardness distribution variance of thin-wall from 31.82 to 13.37. The ultimate tensile strength increased from 219.1 to 227.3 MPa, and the elongation increased from 12.9 % to 14.6 %. Based on the high-speed camera observation, the study discussed the influence of laser beam oscillation on the droplet transfer and melt flow behavior, as well as the improvement mechanism of deposition quality.

Effects of mechanical recycling on the properties of glass fiber–reinforced polyamide 66 composites in automotive components

Abstract In this study, we aimed to reveal the effective reusability of waste generated during the injection molding process of polyamide 66 (PA66) reinforced with 30 wt% of short glass fiber (PA66-GF30) widely used in the automotive industry. PA66-GF30 was subjected to the three mechanical recycling cycles, including regranulation and reinjection molding steps, and the recycled materials obtained in each of these cycles were included at the ratios of 15, 20, 25, and 30 wt% to the virgin composite. Thermogravimetric analysis and differential scanning calorimeter analyses showed that the number of recycling cycles and recycled material content in the composite had no significant change in the thermal stability and crystallinity degree of the PA66-GF30. The average fiber length determined by optical microscope analysis shifted to lower values from 300–350 to 150–250 μm by increasing the number of recycling cycles and the recycled material content. The fact that the recycled material content in the composite exceeds 25 wt% and the recycling cycle is applied three times played a key role in changing the mechanical and melt flow behaviors of the composite. Tensile strength, elastic modulus, and impact energy slightly decreased while the elongation at break and melt flow index increased.

Potential 3D filament of Janeng (Dioscorea hispida Dennst) starch: Preparation and characterization

The preparation and characterization of filaments from janeng have been studied. The janeng filament (PCl-JS) process starts with the preparation and gelatinization of janeng starch, and then the resulting starch gelatinization, which is usually called thermoplastically processable starch (TPS) is carried out by filament processing by mixing PCl-g-GMA and JS at a temperature of 170 °C and 80 rpm for 15 min. The prepared filaments were analyzed. SEM studies show that the fracture surface of PCl-JS0 filaments provides a uniform fiber dispersion, in contrast to the morphology showing large and interconnected starch domains as the starch concentration increases from 1% to 9%. The intensity of hydrogen bonds observed in the spectrum via FTIR increased in band as the concentration of JS increased. XRD analysis observed that the crystallinity and crystal size of filaments without starch were higher than those of other PCl filaments that had undergone modification with starch. Mechanical analysis showed that starch did not have a negative effect on the tensile strength of the filaments, indicating good compatibility between JS and the PCl matrix. When the additional concentration of JS increased to 9%, the strength of PCl-JS filaments increased to 37 MPa, which was caused by the higher crystallinity induced by starch. The glass temperature of the filament sample was observed using DSC, which showed that PCl without JS occurred at 48.2 °C and shifted (+2 °C) towards 49.4 °C when JS was added. For all DSC curves, the exothermic peak was observed around 56–59 °C. The melt flow behavior of PCl-JS filaments decrease with increasing starch content.

In-situ monitoring plume, spattering behavior and revealing their relationship with melt flow in laser powder bed fusion of nickel-based superalloy

Laser powder bed fusion (LPBF) is a highly dynamic and complex physical process, and single-track defects tend to accumulate into non-negligible internal defects of parts. The nickel-based superalloy single track was fabricated by LPBF, and its plume and spattering behavior were monitored in situ and recorded in real time based on image recognition and tracking in this study. The relationship among laser energy density, melt flow, plume and spattering behavior during LPBF was discussed. Volumetric energy density had limitations as a design parameter for LPBF. However, we found that plume and spattering behavior can be used as real-time design parameters for the processing of LPBF parts and implemented the initial velocity statistics for LPBF single-track spattering based on the centroid extraction algorithm. The influence of melt flow evolution paths on the spattering and plume behavior in three different melting modes was revealed, and a shift in plume behavior was found in the overlap region of the additive substrate. This study provides a new method for obtaining statistics of spattering-related physical quantities in the melting mode, which is beneficial for the development of processing methods to mitigate the instability of the LPBF process.

High biomass filled biodegradable plastic in engineering sustainable composites

The production of single-use, non-renewable plastic has persistently impacted the environment through non-biodegradable plastic accumulation. Injection-moulded biodegradable polymer blend [poly(butylene succinate-co-butylene-adipate) (PBSA) and poly(butylene adipate-co-terephthalate) (PBAT)] with an inexpensive filler, walnut shell powder (WSP), enables an appropriate melt flow behaviour after incorporating compatibilizer as confirmed by rheological analysis. The sustainable composites with 60 wt% WSP showed a decrement of 68.4% in tensile strength as compared to PBSA/PBAT blend. However, the inclusion of a 5 wt% compatibilizer in PBSA/PBAT/60wt%WSP composite increased tensile strength by 48.7%, indicating improved interfacial adhesion. Further, the improvements in tensile (694%) and flexural moduli (461%) of PBSA/PBAT blend were observed with the addition of 60 wt% WSP in presence of 7 wt% compatibilizer due to fibrillar morphology of filler. Thus, signifying enhanced stiffness with increased filler, leading to a composite suitable for rigid packaging. Scanning electron microscopy (SEM) confirmed an improved adhesion between matrix and filler interfaces with the addition of a compatibilizer as gaps decreased, subsequently leading to increased mechanical properties. The novelty of this work establishes a high loading of filler can be incorporated with biodegradable polymers and improved properties in presence of compatibilizer makes it more suitable for injection moulding applications to produce a low-cost biocomposite capable of being used as a single-use plastic alternative in rigid packaging.

Investigations on dross formation susceptibility in laser fusion cutting of different stainless steel compositions with emphasis on minor element effects

The problem of variable susceptibility to dross formation or cast-to-cast variations in the performance of solid-state laser fusion cutting of 2 mm stainless steel sheets is investigated. The conducted study considered five different steel batches that each fully meets the material specifications of AISI 304 steel but show variations in minor element concentrations, particularly with respect to the sulfur content. Based on the hypothesis that the dross formation phenomenon correlates with surface tension and viscosity of the melt, the general melt flow behavior of the batches was first characterized by complementary experimental and simulative investigations. This combined approach allowed for a qualitative distinction of batches with a primary negative or positive temperature coefficient (NTC/PTC) of surface tension. Subsequent cutting experiments on qualitatively different batches with variations in cutting speed and gas pressure give evidence that an experienced wider processing window for dross-free cuts relates to PTC batches. However, these batches showed more irregular cut edge topography with slightly increased roughness values. It is consequently concluded that proper quality management in laser cutting of different batches of a material needs to consider the real composition of the materials being cut.

Additive manufacturing of nano-W composite high Nb-TiAl alloys fabricated via selective laser melting

The microstructure instability of high Nb-TiAl alloy at high temperature for a long time severely limits the use of TiAl alloys in more complex environments. Refractory metal W nanoparticles can effectively stable microstructure as an additional second phase due to its high melting point. Meanwhile, the microstructure can be further refined by combining additive manufacturing technology. In this work, the flow of melt during the selective laser melting (SLM) process is simulated by finite element method, and the melt flow behavior is mainly affected by the scanning speed. Preparation of nano-W composite TiAl alloys by SLM, and the higher scanning speed, the nano-W particles tend to more uniform dispersion. Nano-W particles not only plays the role of heterogeneous nucleation, but block columnar grains growth, and finally forming the randomly oriented equiaxed grains microstructure.

Extended investigation of an abrupt crystal diameter change during Czochralski silicon growth with transverse magnetic field

An investigation about the phenomenon of an abrupt diameter deviation during Czochralski crystal growth, a characteristic when using a transverse magnet, has been carried out both experimentally and computationally. 300-mm silicon crystals have been pulled under certain conditions and the diameter deviations have been recorded in these processes. Three-dimensional calculations of the melt flow have been performed using CGSim Flow Module 3D, accounting for distribution of the actual non-uniform magnetic field, to accurately simulate the heat transfer and melt flow for selected growth stages along the entire process. The sudden change of melt temperature near the triple point that leads to the diameter deviation, is attributed to the evolution of melt flow pattern, which can be altered by positioning the magnet at a different height. The discovery of such melt flow behavior proposes an effective solution to eventually eliminate the abrupt diameter deviation during body growth. The visualization of the melt flow transformation by 3-D simulation offers another adjustability to the process of modern industrial crystal growth with transverse magnet. The mechanism of how the magnet position impacts the melt flow is also discussed.

Defect elimination and microstructure improvement of laser powder bed fusion β-solidifying γ-TiAl alloys via circular beam oscillation technology

To eliminate metallurgical defects and improve microstructures in laser powder bed fusion (LPBF) β-solidifying γ-TiAl alloys, circular beam oscillation technology was used to fabricate a Ti–43Al–9V-0.5Y alloy in this work. The metallurgical defects and microstructures under conventional linear (non-oscillating) scanning and circular oscillating scanning are first studied in comparison. Then, the microstructural evolution and defect suppression mechanisms under circular oscillating scanning are revealed based on the melt flow behavior. In contrast to the non-oscillating scanning, circular oscillating scanning can better eliminate the pores and cracks of LPBFed Ti–43Al–9V-0.5Y alloy. As the oscillating velocity is decreased, the crack density decreases and the microstructure changes from columnar to equiaxed grains. The crack-free samples with a relative density of 99.98% and fine equiaxed grains are obtained as the oscillating velocity is less than or equal to 100 mm/s. The microhardness (473–581 Hv) of the non-oscillating samples is higher than that (440–487 Hv) of the oscillating samples. The room-temperature compressive strengths (∼1222 MPa and ∼1931 MPa) and tensile strength (∼253 MPa) of the crack-free oscillating LPBFed samples are superior to those of the as-cast counterparts. The suppression of pores is ascribed to the improved keyhole stability, enhanced melt convection as well as escape of bubbles under circular beam oscillation. When the oscillating velocity is less than or equal to 100 mm/s, the sufficient stirring effect of the laser beam promotes the formation of fine equiaxed grains and the reduction of brittle B2 phase content, which effectively inhibits cracking.