Selective Laser Melting Process Research Articles

Microstructural evolution and magnetic influence mechanism of Cr in-situ alloying SLM-formed NiFeMo alloys

NiFeMo is prevalently employed in the field of aerospace and electronic devices owing to its excellent soft magnetic properties. Besides, the incorporation of elements through in-situ alloying presents a novel strategy for performance modulation in Selective Laser Melting (SLM), presenting a novel pathway toward the advancement of soft magnetic materials. In this study, (NiFeMo)100-xCrx alloys (x=0 wt%, 0.5 wt%, 1.0 wt%, 1.5 wt%, 2.0 wt%, 2.5 wt%) were prepared utilizing Cr in-situ alloying SLM. The magnetic properties as well as microstructural characterization were conducted by employing X-ray diffraction (XRD), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), high-resolution transmission electron microscopy (HRTEM) (Tecnai-G2-F30), and direct current B-H hysteresis curve testing equipment (MATS-2010S). The results indicate that the microstructure of the SLM-formed NiFeMo alloy through in-situ chromium alloying is predominantly characterized by columnar grains growing along the build direction. With an increase in the in-situ alloying ratio of chromium, the lattice parameters of the FCC phase structure of the NiFeMo alloy decrease from 3.582 Å to 3.503 Å, the average grain size monotonically decreases, and the maximum texture strength monotonically weakens. Furthermore, during the in-situ alloying SLM process, chromium is dissolved into the FCC γ-(Ni, Fe) of the NiFeMo alloy, forming dispersed, chromium-rich precipitates of larger sizes. This leads to a reduction in the intrinsic magnetic properties of the NiFeMo alloy, affecting the exchange coupling interaction between magnetic atoms and the motion of magnetic domains. Compared to the NiFeMo alloy, the saturation magnetization of the (NiFeMo)97.5Cr2.5 alloy is reduced to 0.4685 T, and the coercive force is increased to 37.7 A/m. However, when the chromium content is 1 wt%, the initial magnetic permeability of the (NiFeMo)99Cr1 alloy is 2.337 mH/m, which is an enhancement of 1.9422 mH/m compared to the NiFeMo alloy.

Fabricating diamond bit by selective laser melting and its drilling performance evaluation

Diamond abrasive tools play an important role in efficient and precision machining of difficult-to-cut materials. As the traditional tool manufacturing process is difficult to meet the integrated molding preparation of complex structures, the use of selective laser melting (SLM) technology to manufacture diamond tools with functions and structures has become a research hotspot in recent years. In this paper, the feasibility and wear characteristics of diamond bits prepared by SLM using AlSi7Mg as metal matrix are investigated. The optimal parameter combination of diamond/AlSi7Mg mixture was obtained through orthogonal experiments, in which the powder layer thickness was 30 μm, the laser power was 300 W, the scanning speed was 3000 mm/s, and the scanning spacing was 120 μm. This parameter combination realized the improvement of the mechanical properties and the decrease of the porosity. Two types of bits with and without groove-structure (Labeled as Bit-G and Bit-N) were fabricated and their drilling performance were compared by processing BK7 optical glass. The results show that the Bit-G has more excellent machining performance, including lower drilling force, better hole quality and longer service life. According to the simulation results, the self-sharpening cycle of the Bit-G’s wear characteristics can be attributed to the groove structure that allows the coolant to be fully utilized in the bit/workpiece contacting area. This paper demonstrates the feasibility of the SLM process for the preparation of diamond tools and comprehensively analyzes the wear process, which provides reference value for further research on this process for the manufacturing of diamond abrasive tools.

Evolution of mechanical properties and microstructure of selective laser melted AlSi10MgMn alloy with different post heat treatments

This study investigated the effects of various post heat treatments on the mechanical properties and microstructure evolution of an AlSi10MgMn alloy containing 0.5 wt% Mn produced by the selective laser melting process for the first time. The microstructures under different conditions were analyzed using optical microscopy, scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy. In the as-manufactured (F) condition, the alloy exhibited an ultimate tensile strength (UTS) of 486 MPa, a yield strength (YS) of 299 MPa, and an elongation of 10.3 %. After a T5 treatment, the UTS and YS increased to 532 MPa and 386 MPa, respectively, resulting in a remarkable 30 % improvement in YS compared to the F state. The tensile properties achieved by the new alloy were considerably higher than those reported for conventional AlSi10Mg alloys in the F, T5, and T6 conditions. The T5 treatment promoted the precipitation of a large fraction of Si-rich nanoparticles and MgSi-based precipitates without disrupting the Si-rich network. After a T6 treatment, the Si-rich network completely disappeared, and the main strengthening phase was MgSi-based precipitates accompanied by α-Al(Mn,Fe)Si dispersoids induced by the Mn addition. Using microstructure-based constitutive models, the strengthening contributions of various microstructural components to mechanical strength in different processing conditions were analyzed.

Progress in the Study of Quality and Mechanical Properties of Selective Laser Melting Molded Parts

Abstract: Selective laser melting (SLM) is considered to be a widely promising additive manufacturing technology with the advantages of high machining precision, high manufacturing freedom, and short cycle time, which is widely used in aerospace, the integration of medicine, and industry, chemical, and other fields. The research progress on the temperature field, stress field, forming quality, and mechanical properties during the SLM manufacturing process is reviewed. The study aims to systematically analyze how SLM process parameters affect the temperature field, stress field, forming quality, and mechanical properties, and to discuss the importance of the selection of process parameters and performance regulation to achieve high-quality, highperformance metal parts. The effects of SLM process parameters on temperature field, stress field, surface roughness, densification, hardness, strength, and fatigue properties are analyzed and summarized. The importance of process parameters in the SLM forming procedure in the quality of formed components is emphasized, and conducting an in-depth study on the optimization and performance regulation of the process parameters is of great significance in achieving the high quality and performance of metal parts. With the rapid advancement of technology, the potential of SLM technology in terms of molding quality and mechanical performance has become increasingly significant, heralding significant breakthroughs. These potential breakthroughs will greatly promote the widespread application of SLM technology in various industries, thus more efficiently meeting the growing needs and expectations of industries such as petrochemicals, transportation, aerospace, nuclear energy, as well as food and medical sectors.

Selective Laser Melting Process Optimization and Mechanical Properties Evolution of AlSi10Mg by Determining Temperature of the Build Chamber using Arduino IDE and Coding Algorithm

Selective Laser Melting Process Optimization and Mechanical Properties Evolution of AlSi10Mg by Determining Temperature of the Build Chamber using Arduino IDE and Coding Algorithm

Optimizing Selective Laser Melting of Inconel 625 Superalloy Through Statistical Analysis of Surface and Volumetric Defects

This article delves into optimizing and modeling the input parameters for the selective laser melting (SLM) process on Inconel 625. The primary aim is to investigate the microstructure within the interlayer regions post-process optimization. For this study, 100 layers with a thickness of 40 µm each were produced. Utilizing the design of experiments (DOE) methodology and employing the Response Surface Method (RSM), the SLM process was optimized. Input parameters such as laser power (LP) and hatch distance (HD) were considered, while changes in microhardness and roughness, Ra, were taken as the responses. Sample microstructure and surface alterations were assessed via scanning electron microscopy (SEM) analysis to ascertain how many defects and properties of Inconel 625 can be controlled using DOE. Porosity and lack of fusion, which were due to rapid post-powder melting solidification, prompted detailed analysis of the flaws both on the surfaces of and in terms of the internal aspects of the samples. An understanding of the formation of these imperfections can help refine the process for enhanced integrity and performance of Inconel 625 printed material. Even slight directional changes in the columnar dendrite structures are discernible within the layers. The microstructural characteristics observed in these samples are directly related to the parameters of the SLM process. In this study, the bulk samples achieved a microhardness of 452 HV, with the minimum surface roughness recorded at 9.9 µm. The objective of this research was to use the Response Surface Method (RSM) to optimize the parameters to result in the minimum surface roughness and maximum microhardness of the samples.

Research on the Mechanical Response and Constitutive Model of 18Ni300 Manufactured by SLM with Different Build Directions.

Metals manufactured by selective laser melting (SLM) with different directions exhibit different mechanical properties. This study conducted dynamic and static mechanical tests using a universal testing machine and split-Hopkinson bar (SHPB). The mechanical properties of 18Ni300 with 0° and 90° build directions manufactured by SLM were compared, and the micro-structure properties of the two build directions were analysed by metallographic tests. The Johnson-Cook (J-C) constitutive model was fitted according to the experimental results, and the obtained constitutive parameters were verified by numerical simulations. The results revealed that the constitutive model could predict the mechanical properties of 18Ni300 in a dynamic state. The build direction had little influence on the mechanical properties in a static state, but there was a significant difference in the dynamic state. The difference in the dynamic compressive yield strength of the 18Ni300 material manufactured by SLM with two build directions was 9.8%. The SLM process can be improved to produce 18Ni300 with uniform mechanical properties by studying the reasons for this difference.

Selective Laser Melting Process Optimization and Mechanical Properties Evolution of AlSi10Mg by determining temperature of the build chamber using Arduino IDE and coding algorithm

Unlike conventional methods that involve removing components from a product, the groundbreaking idea behind additive manufacturing (AM) is the gradual creation of materials. A computer-controlled laser is often used in additive manufacturing to shape and consolidate powder feedstock in a layer-by-layer fashion to arbitrary shapes. The aerospace, defense, automotive, and biomedical sectors have high standards, and AM is now being refined to create complex-shaped functional metallic components out of metals, alloys, and other materials. Lightweight structural components with series similar mechanical characteristics may be produced using Selective Laser Melting (SLM), one of the AM technologies that eliminate the requirement for part specific tooling or downstream sintering procedures, among other things. The low weight and excellent mechanical and chemical qualities of aluminium make it an ideal material for such environmentally designed components. We need further information on how processing circumstances and material qualities affect the microstructural and mechanical properties of AM produced components as well as the metallurgical processes that produce them. Following this, we provide a comprehensive overview of AM's material and process components, including the mechanical and microstructural features of AM-processed parts as well as the physical characteristics of AM-optimized materials. Ultimately, the samples made using SLM-Alsi10Mg demonstrated an ultimate tensile strength of 150 MPa, yield strength of 120 MPa, and an elongation of 20%, as determined by the testing data. Mechanical properties of AlSi10Mg, additive manufacturing, laser powder bed fusion, selective laser melting, and related terms.

Investigations on the influence of hot rolling on the creep characteristics of additively manufactured Mg-5Ag alloy

The requirement for lightweight materials that can survive increasingly severe conditions for aerospace components has fueled the research on magnesium alloys. The current work investigates the influence of hot rolling on the creep characteristics of the Mg-5Ag alloy that is fabricated through a selective laser melting process. The creep properties of parent material (PM) and hot-rolled specimens (HRA) are determined by indentation creep tests at 250 °C, 275 °C, and 300 °C. The microstructural evolution, phase transformation kinetics, and texture evolution were deduced using instrumental analysis, including SEM, EBSD, TEM, and XRD. The specimen PM features α-Mg grains with intermetallic Mg-Ag particles along grain boundaries and random grain orientations with low-angle boundaries. However, specimen HRA has a more fraction of Mg-Ag precipitates, a dominant (0001) grain orientation, and higher peak intensity from the (002) plane. The HRA specimen also demonstrates higher apparent activation energies, attributed to microstructural changes from hot rolling. The results show that the creep resistance of the hot rolled Mg-5Ag alloy is superior to as-fabricated Mg-5Ag alloy based on the creep velocity, stress exponent, and apparent activation energy.

Improving fatigue behavior of selective laser melted 316 L stainless steel by ultrasonic-assisted burnishing

PurposeIn this study, two postprocessing techniques, namely, conventional burnishing (CB) and ultrasonic-assisted burnishing (UAB), were applied to improve the fatigue behavior of 316 L stainless steel fabricated through selective laser melting (SLM). The effects of these processes on surface roughness, porosity, microhardness and fatigue performance were experimentally investigated. The purpose of this study is to evaluate the feasibility and effectiveness of ultrasonic-assisted burnishing as a preferred post-processing technique for enhancing the fatigue performance of additively manufactured components.Design/methodology/approachAll samples were subjected to a sandblasting process. Next, the samples were divided into three distinct groups. The first group (as-Built) did not undergo any additional postprocessing, apart from sandblasting. The second group was treated with CB, while the third group was treated with ultrasonic-assisted burnishing. Finally, all samples were evaluated based on their surface roughness, porosity, microhardness and fatigue performance.FindingsThe results revealed that the initial mean surface roughness (Ra) of the as-built sample was 11.438 µm. However, after undergoing CB and UAB treatments, the surface roughness decreased to 1.629 and 0.278 µm, respectively. Notably, the UAB process proved more effective in eliminating near-surface pores and improving the microhardness of the samples compared to the CB process. Furthermore, the fatigue life of the as-built sample, initially at 66,000 cycles, experienced a slight improvement after CB treatment, reaching 347,000 cycles. However, the UAB process significantly enhanced the fatigue life of the samples, extending it to 620,000 cycles.Originality/valueAfter reviewing the literature, it can be concluded that UAB will exceed the capabilities of CB in terms of enhancing the surface roughness and, subsequently, the fatigue performance of additive manufactured (AM) metals. However, the actual impact of the UAB process on the fatigue life of AM products has not yet been thoroughly researched. Therefore, in this study, this paper used the burnishing process to enhance the fatigue life of 316 L stainless steel produced through the SLM process.

Effects of strain rate and low temperature on dynamic behaviors of additively manufactured CoCrFeMnNi high-entropy alloys

With the increasing demand for high-performance alloys in extreme environments, there has been an active development of new materials. High-entropy alloys (HEAs) are considered a promising choice due to their exceptional properties. Even though HEAs exhibit remarkable mechanical properties, only a limited number of studies have explored the mechanical properties and microstructures of additively manufactured HEAs under extreme conditions. In this work, the dynamic mechanical properties at high strain rates and different temperatures (i.e., 293 K and 77 K), as well as quasi-static mechanical properties for the CoCrFeMnNi HEAs fabricated by selective laser melting (SLM) are investigated. Microstructure observations have demonstrated that the as-printed sample displays a single face-centered cubic (FCC) phase with a columnar dendrite feature. Within dendrites, a large number of dislocations and substructures appear due to the applied high cooling rates during the SLM process. The as-printed sample exhibits a significant strain rate dependence from quasi-static to dynamic loading during deformation. Compared to the quasi-static mechanical properties, the as-printed HEA reveals higher dynamic yield strength (e.g., ∼1081 MPa and ∼1020 MPa along the build and scanning directions under 2800 s−1, respectively), more pronounced strain-hardening behavior, and larger remarkable plasticity under dynamic loading at cryogenic temperatures. When subjected to increasing strain rates ranging from 0.001 s−1 to 3500 s−1 at 293 K, the yield strength of the as-printed HEAs exhibits a notable enhancement, increasing from ∼517 MPa to ∼723 MPa along the BD direction, and from ∼545 MPa to ∼667 MPa along the SD direction. The corresponding variation in the strength of the BD samples is more pronounced than that of the SD samples. The enhancement in strength should be attributed to the differences in the features of grain orientation and dislocation distribution along different build directions, as well as the strain rate dependence. During plastic deformation, the dominant mechanisms of dislocation slips and deformation twins (DTs) are transformed into multi-stage-twin-controlled ones at cryogenic temperatures, which is beneficial to improve the strain hardening rate and plasticity. The present studies provide a deep understanding of the deformation mechanism of HEAs under extreme conditions and help promote the application of HEAs in the future.

Eliminating metallurgical defects and achieving strength-ductility combination in selective laser melted martensitic stainless steel through high-pressure annealing

Due to high difficulty in fabricating and processing high-strength metals, additive manufacturing has been considered to have broad prospects compared to the traditional casting means. However, unavoidable metallurgical defects and strength–ductility trade-off dilemma have become Achilles' heels for their practical applications. In this work, one high-pressure annealing (HPA) strategy was introduced to process the selective laser melted (SLM) martensitic stainless steel. The microstructures and mechanical properties of as-built, high temperature annealing and HPA and as-rolled SLM samples were systematically investigated. It was found that the HPA treatment makes the stainless steel achieve the significant yield strength of 1828 MPa and the comparable plastic strain of 36.2% compared to other samples. The pores and laminar structures from the SLM process were eliminated by HPA. What is more, the HPA treatment results in uniform carbide precipitation, grain refinement and nanoscale heterogeneous structure comprising a series of coarse and fine grains. The physical mechanism for nanoscale heterogeneous structure induced by HPA was discussed from the perspective of the cooperative effect of temperature and pressure. Additionally, the strengthening contributions from grain refinement, carbide precipitation, dislocation hardening, heterogeneous structure and pore closure were quantitatively determined. The current study not only reveals the comprehensive effect of temperature and pressure on microstructure and mechanical properties, but also establishes HPA as an effective method to evade the strength-ductility trade-off in alloys fabricated by additive manufacturing.

Simulation of the selective laser sintering/melting process of bioactive glass 45S5

Additive manufacturing processes, including selective laser sintering (SLS) and selective laser melting (SLM), are rapidly developing industrial fields that require scientific support. Although SLS and SLM are very similar, the level of modeling and simulation of SLM is much higher than that of SLS. This results in the number of publications before 2024 according to Web of Science with SLM simulation approximately five times more than with SLS. To test the possibility of adequate SLS simulations, a platform based on the lattice Boltzmann method (LBM), previously developed and applied to model the SLM process, was used. In addition, the possibility of modeling similar processes (SLM, SLS, and SLS/SLM) using the same modeling tool on the same modeling platform is important. The objective of this paper is to present a model of the SLS process and confirmation of the possibility of using LBM for simulation of the SLS process. A simulation of SLS and SLM with the use of LBM, and qualitative comparison of the results of these simulation for bioactive glass 45S5 is the basis of the methodology used for the research. The simulation presented in this study confirmed the possibility of simulating SLM, SLS processes using common principles, approaches, and models. The results of SLS process simulations can be treated as qualitative and require further verification, whereas SLM simulations have been previously verified. The application of the lattice Boltzmann method, which is a computational fluid dynamics (CFD) method, opens the possibility of using almost every CFD method for the simulation of several kinds of SLS, and can accelerate research in this field.

A Meshless Method of Radial Basis Function-Finite Difference Approach to 3-Dimensional Numerical Simulation on Selective Laser Melting Process

Selective laser melting (SLM) is a rapidly evolving technology that requires extensive knowledge and management for broader industrial adoption due to the complexity of phenomena involved. The selection of parameters and numerical analysis for the SLM process are both costly and time-consuming. In this paper, a three-dimensional radial basis function-finite difference (RBF-FD) meshless model is introduced to accurately and efficiently simulate the molten pool size and temperature distribution during the SLM process for austenitic stainless steel (AISI 316L). Two different volumetric moving heat source models were presented, namely the ray-tracing method heat source model and the double-ellipsoidal shape heat source model. The temperature-dependent material properties and phase change process were also considered, based on experiments and effective models. Results of the model for the molten pool size were validated with those of the literature. The proposed approach can be used to predict the effect of different laser power and scan speed on the molten pool size and temperature gradient along the depth direction. The result reveals that the depth of the molten pool is more sensitive to laser power than scan speed. Under the same scan speed, a 22% change in laser power (45 ± 10 W) affects the maximum temperature proportionally by about 9%. The developed algorithm is computationally efficient and suitable for industrial applications.

Structural analysis of selective laser melted copper-tin alloy

Additively manufactured complex geometries from copper alloys with high thermal and mechanical properties have drawn the attention of researchers. The present contribution explores the additive manufacturing (AM) of copper-based alloys from powder particles intended for heat sink and heat exchange applications. Selective laser melting (SLM) parameters featuring low laser beam power (160 W), moderate scanning speed (320 mm/s), and high energy density (200 J/mm³) were employed to fabricate dense components from CuSn10 particles. The present work deal with structural analysis and precision investigation of microfabrication, particularly in Struts, Tubes, and Fins. Mechanical properties (compression and hardness) for Strut structure, differential pressure evaluations for Tube structure, and analyses of thermal and electrical conductivities for Fin structure were investigated. The results showed an improvement in strength compared to those of pure copper, facilitating ease of AM. The obtained results affirm the feasibility of AM, demonstrating the successful creation of complex and combined solid-porous structures using SLM process from Cu alloys. A comprehensive structural investigation and characterization of the Cu–Sn alloy is presented here, aiming to establish a standardized approach for analysing Cu alloys. The results indicate that small-scaled structures fabricated via CuSn10 alloy exhibits a thermal conductivity of 34.3 W·m⁻¹·K⁻¹, an electrical conductivity of 4.72×10⁶ S/m, a hardness of 119 HV-50, a uniform surface roughness of 6 µm, and can withstand a force loading of 1 kN.

Numerical and experimental investigation on flexural properties of selective laser melting (SLM) manufactured strut lattices structures from Ti-6Al-4V and Inconel 625

Lattice structures hold a significant importance in the aerospace industry due to their ability to tailor the physical, thermal, and mechanical properties of complex components for optimal performance. This study is focused on evaluating the flexural properties of four lattice configurations - re-entrant, truncated octahedron, Kelvin, and octet cells - through static finite element analysis (FEA) and experimental three-point bending tests, as well as examining their microstructural features (as they affect the materials’ mechanical properties). High-performance alloys used for gas turbines components manufacturing, Ti-6Al-4 V and Inconel 625, were fabricated using selective laser melting (SLM) process. The necessity of this research resulted from the lack of information in the scientific literature regarding flexural properties of various additive manufactured cell types and metallic materials. The aim was to compile data that could be used to create a comprehensive database for various industrial applications. Findings from both simulations and experimental analyses indicated that the octet cell had the highest performance, with experimentally measured flexural strengths of 878 MPa for Ti-6Al-4V, respective 674 MPa for Inconel 625. Contrarily, the re-entrant cell exhibited the lowest performance, with flexural strengths of 125 MPa for Ti-6Al-4V and 116 MPa for Inconel 625. Failure in the re-entrant cells was attributed to the bending fracture of vertical rods at the connecting nodes or lattice struts, while other cell types experienced damage through a combination of bending and shear mechanisms. Dimensional deviations observed in all specimens were attributed to defects such as surface roughness, the stair-stepping effect, and internal stresses.

The effect of diamond grain size on the formability and mechanical property of 3D-printed diamond tool

Because of the flexibility of structure design and material design, 3D-printed metal-bonded diamond tool is expected to be the next generation of diamond tools. In this paper, the selective laser melting process is utilized to fabricate the metal-bonded diamond tool based on the mixed powders consisted of AlSi10Mg powder and diamond powder. Relative density, material characterization and mechanical property are measured to figure out the effect of diamond grain size on the formability and property of 3D-printed diamond tool with diamond grain size from 200 mesh to 500 mesh. The results suggest that, when the diamond volume fraction stays the same, with the diamond grain size decreasing, the relative density and main mechanical properties descend due to the increment of defects. Furthermore, the 3D-printed diamond tool with evenly distributed and firmly embedded diamond abrasives can be fabricated and corresponding mechanical properties can meet the requirement of diamond tool.

Investigation on selective laser-melted AlSi10Mg micro-struts: influence of processing parameters on dimensional accuracy, molten pool morphology and microhardness

PurposeThis study aims to address the limited understanding of the complex correlations among strut size, structural orientation and process parameters in selective laser melting (SLM)-fabricated lattice structures. By investigating the effects of crucial process parameters, strut diameter and angle on the microstructure and mechanical performance of AlSi10Mg struts, the research seeks to enhance the surface morphologies, microstructures and mechanical properties of AM lattice structures, enabling their application in various engineering fields, including medical science and space technologies.Design/methodology/approachThis comprehensive study investigates SLM-fabricated AlSi10Mg strut structures, examining the effects of process parameters, strut diameter and angle on densification behavior and microstructural characteristics. By analyzing microstructure, geometrical properties, melt pool morphology and mechanical properties using optical microscopy, scanning electron microscope, energy dispersive X-ray spectroscopy and microhardness tests, the research addresses existing gaps in knowledge on fine lattice strut elements and their impact on surface morphology and microstructure.FindingsThe study revealed that laser energy, power density and strut inclination angle significantly impact the microstructure, geometrical properties and mechanical performance of SLM-produced AlSi10Mg struts. Findings insight enable the optimization of SLM process parameters to produce lattice structures with enhanced surface morphologies, microstructures and mechanical properties, paving the way for applications in medical science and space technologies.Originality/valueThis study uniquely investigates the effects of processing parameters, strut diameter and inclination angle on SLM-fabricated AlSi10Mg struts, focusing on fine lattice strut elements with diameters as small as 200 µm. Unlike existing literature, it delves into the complex correlations among strut size, structural orientation and process parameters to understand their impact on microstructure, geometrical imperfections and mechanical properties. The study provides novel insights that contribute to the optimization of SLM process parameters, moving beyond the typically recommended guidelines from powder or machine suppliers.

Phase-field based modeling and simulation for selective laser melting techniques in additive manufacturing

In this study, we develop a phase-field model to describe the solid–liquid phase changes, heat conduction phenomena, during the selective laser melting process. This model is based on the variational principle of minimizing the free energy functional. The proposed model integrates the phase-field equation and the energy equation, which are used to capture the dynamical behavior of the interfacial evolution. We use the semi-implicit Crank–Nicolson scheme and central difference to ensure second-order accuracy in time and space. The numerical scheme is unconditional energy stable. This paper rigorously proves the energy stability of the phase-field model of the Selective Laser Melting process, which confirms the numerical stability and the physical rationality of the solution. Various numerical experiments are performed to verify the robustness of our proposal model. This model can effectively simulate the energy transfer and shape structure changes of the products during the selective laser melting manufacturing process, which provides a reliable guarantee for predicting and optimizing the quality and performance of the selective laser melting process additive manufacturing process.

Study of Eddy Current Testing Ability on SLM Aluminium Alloy.

The detection of defects in aluminium alloys using eddy current testing (ECT) can be restricted by higher electrical conductivity. Considering the occurrence of discontinuities during the selective laser melting (SLM) process, checking the ability of the ECT method for the mentioned purpose could bring simple and fast material identification. The research described here is focused on the application of three ECT probes with different frequency ranges (0.3-100 kHz overall) for the identification of artificial defects in SLM aluminium alloy AlSi10Mg. Standard penetration depth for the mentioned frequency range and identification abilities of used probes expressed through lift-off diagrams precede the main part of the research. Experimental specimens were designed in four groups to check the signal sensitivity to variations in the size and depth of cavities. The signal behavior was evaluated according to notch-type and hole-type artificial defects' presence on the surface of the material and spherical cavities in subsurface layers, filled and unfilled by unmolten powder. The maximal penetration depth of the identified defect, the smallest detectable notch-type and hole-type artificial defect, the main characteristics of signal curves based on defect properties and circumstances for distinguishing between the application of measurement regime were stated. These conclusions represent baselines for the creation of ECT methodology for the defectoscopy of evaluated material.