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Optimization of production process of Mg tubes produced with laser dieless drawing method and related microstructural analysis
摘要： This contribution deals with a laser dieless drawing method in which tubes (AZ31 magnesium alloy) with small dimensions are produced from previously extruded tubes with a larger diameter. The process involves local laser heating of a tube with concurrent drawing and rotation of a sample. The control parameters need to be optimized in order to get a good quality tube with low damage and regular diameter. Here, a previously developed finite element (FE) model is used for the numerical optimization. The optimization itself is multi-objective, maximizing the uniformity of the resulting tube but concurrently, minimizing its critical deformation. Since one run of the FE code lasts for several days, an approximation by a Radial Basis Function meta-model (surrogate) is used. Results reveal that there is only a very limited number of combinations of parameters leading to a uniformly shaped tubes. Finally, tubes produced with optimized parameters are analyzed from the microstructural point of view.
关键词： Laser dieless drawing process,Microstructural analysis,Optimization,Numerical modeling,Magnesium alloys
更新于2025-09-12 10:27:22
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Laser Beam Welding of a Low Density Refractory High Entropy Alloy
摘要： The effect of laser beam welding on the structure and properties of a Ti1.89NbCrV0.56 refractory high entropy alloy was studied. In particular, the effect of different pre-heating temperatures was examined. Due to the low ductility of the material, laser beam welding at room temperature resulted in the formations of hot cracks. Sound butt joints without cracks were produced using pre-heating to T ≥ 600 °C. In the initial as-cast condition, the alloy consisted of coarse bcc grains with a small amount of lens-shaped C15 Laves phase particles. A columnar microstructure was formed in the welds; the thickness of the grains increased with the temperature of pre-heating before welding. The Laves phase particles were formed in the seams after welding at 600 °C or 800 °C, however, these particles were not observed after welding at room temperature or at 400 °C. Soaking at elevated temperatures did not change the microstructure of the base material considerably, however, “additional” small Laves particles formed at 600 °C. Tensile test of welded specimens performed at 750 °C resulted in the fracture of the base material because of the higher hardness of the welds. The latter can be associated with the bcc grains refinement in the seams.
关键词： microstructure,mechanical properties,laser beam welding,high entropy alloys
更新于2025-09-12 10:27:22
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Investigation into strength T5К10 hard alloy after volumetric pulsed laser hardening (VPLH)
摘要： The given paper is devoted to the investigation of the phenomenon of shock wave excitation caused by laser impact in hard alloy T5R10 that is widely used for cutting tools manufacturing and for other purposes. The effect of volumetric pulsed laser hardening (VPLH) on the changes in strength of hard alloy T5R10 is considered. The factors influencing the creation of new stable structures in hard alloys are determined.
关键词： Wear resistance,Hard alloys,Hardening,Cutter power,Laser,Strength,X-ray structural analysis
更新于2025-09-12 10:27:22
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The Effects of Feature Sizes in Selectively Laser Melted Ti-6Al-4V Parts on the Validity of Optimised Process Parameters
摘要： Ti-6Al-4V is a popular alloy due to its high strength-to-weight ratio and excellent corrosion resistance. Many applications of additively manufactured Ti-6Al-4V using selective laser melting (SLM) have reached technology readiness. However, issues linked with metallurgical di?erences in parts manufactured by conventional processes and SLM persist. Very few studies have focused on relating the process parameters to the macroscopic and microscopic properties of parts with di?erent size features. Therefore, the aim of this study was to investigate the e?ect of the size of features on the density, hardness, microstructural evolution, and mechanical properties of Ti-6Al-4V parts fabricated using a ?xed set of parameters. It was found that there is an acceptable range of sizes that can be produced using a ?xed set of parameters. Beyond a speci?c window, the relative density decreased. Upon decreasing the size of a cuboid from (5 × 5 × 5 mm) to (1 × 1 × 5 mm), porosity increased from 0.3% to 4.8%. Within a suitable size range, the microstructure was not signi?cantly a?ected by size; however, a major change was observed outside the acceptable size window. The size of features played a signi?cant role in the variation of mechanical properties. Under tensile loading, decreasing the gauge size, the ultimate and yield strengths deteriorated. This investigation, therefore, presents an understanding of the correlation between the feature size and process parameters in terms of the microscopic and macroscopic properties of Ti-6Al-4V parts manufactured using SLM. This study also highlights the fact that any set of optimized process parameters will only be valid within a speci?c size window.
关键词： additive manufacturing,microstructure,tensile behaviour,selective laser melting,titanium alloys,mechanical properties
更新于2025-09-12 10:27:22
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Solid-State Phase Transformations in Thermally Treated Ti–6Al–4V Alloy Fabricated via Laser Powder Bed Fusion
摘要： Laser Powder Bed Fusion (LPBF) technology was used to produce samples based on the Ti–6Al–4V alloy for biomedical applications. Solid-state phase transformations induced by thermal treatments were studied by neutron di?raction (ND), X-ray di?raction (XRD), scanning transmission electron microscopy (STEM) and energy-dispersive spectroscopy (EDS). Although, ND analysis is rather uncommon in such studies, this technique allowed evidencing the presence of retained β in α’ martensite of the as-produced (#AP) sample. The retained β was not detectable by XRD analysis, nor by STEM observations. Martensite contains a high number of defects, mainly dislocations, that anneal during the thermal treatment. Element di?usion and partitioning are the main mechanisms in the α ? β transformation that causes lattice expansion during heating and determines the ?nal shape and size of phases. The retained β phase plays a key role in the α’ → β transformation kinetics.
关键词： X-ray di?raction,neutron di?raction,Ti alloys,phase transformations,thermal treatments,additive manufacturing,scanning transmission electron microscopy,energy-dispersive spectroscopy
更新于2025-09-12 10:27:22
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Aluminium Matrix Composites Produced by Laser Based Additive Manufacturing
摘要： 3D laser metal deposition (LMD) based on the laser cladding is an established technique for additive manufacturing tasks. Also the laser cladding is a well-known technique to produce aluminum matrix composites reinforced by Si particles. High cooling rates typical for laser treatment enable to eliminate coarse Si particles formation which is a substantial disadvantage of in-situ Al-Si composites produced by traditional manufacturing processes like casting. The coarse Si particles formation reduces Al-Si composites mechanical properties. Extremely non-equilibrium solidification conditions typical for micro LMD process allow to obtain a further structure refinement and its mechanical properties improvement. In this paper the in-situ Al-Si composites produced by micro LMD process with different parameters sets were investigated by fine structure X-ray analysis. The structure and phase composition of in-situ Al-Si composites were described. The influence of cladding parameters on Al-Si composites structure was investigated.
关键词： MMC,aluminium matrix composites,Laser micro cladding,thin-wall parts,fine structure,additive manufacturing,aluminium alloys,X-ray analysis,thin wall
更新于2025-09-12 10:27:22
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A prediction model for finding the optimal laser parameters in additive manufacturing of NiTi shape memory alloy
摘要： Shape memory alloys (SMAs) have been applied for various applications in the fields of aerospace, automotive, and medical. Nickel-titanium (NiTi) is the most well-known alloy among the others due to its outstanding functional characteristics including superelasticity (SE) and shape memory effect (SME). These particular properties are the result of the reversible martensite-to-austenite and austenite-to-martensite transformations. In recent years, additive manufacturing (AM) has provided a great opportunity for fabricating NiTi products with complex shapes. Many researchers have been investigating the AM process to set the optimal operational parameters, which can significantly affect the properties of the end-products. Indeed, the functional and mechanical behavior of printed NiTi parts can be tailored by controlling laser power, laser scan speed, and hatch spacing having them a crucial role in properties of 3D-printed parts. In particular, the effect of the input parameters can significantly alter the mechanical properties such as strain recovery rates and the transformation temperatures; therefore, using suitable parameter combination is of paramount importance. In this framework, the present study develops a prediction model based on artificial neural network (ANN) to generate a nonlinear map between inputs and outputs of the AM process. Accordingly, a prototyping tool for the AM process, also useful for dealing with the settings of the optimal operational parameters, will be built, tested, and validated.
关键词： Shape memory alloys,Modeling,NiTi,Artificial neural network,Additive manufacturing
更新于2025-09-12 10:27:22
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Titanium for Consumer Applications || Bone regeneration on implants of titanium alloys produced by laser powder bed fusion: A review
摘要： Bone regeneration on biomaterials is a topic of increased interest due to the possibility of creating implants that existing bone can attach to. Titanium alloys are very suitable for this purpose and have been proven to be biocompatible, while also having suitable mechanical properties [1]. Moreover, titanium alloys are one of the most widely investigated materials for metal additive manufacturing (AM), which means that custom-designed implants can be manufactured reliably by AM. The AM technology best suited to this is powder bed fusion; laser powder bed fusion (LPBF) in particular holds some advantages. In this chapter, we investigate the current state of the art for the production of pure Ti and Ti6Al4V implants by LPBF, focusing on the requirements and capabilities for osseointegration. The first section discusses bone architecture and requirements for bone implants in general, identifying different requirements for different types of implants, and describing the various bone growth processes in more detail. This is followed by a section on surface structuring; the surface morphology and chemistry strongly influence the initial stages of bone growth, making it critical to the success of such implants. The next section describes porous structures, also known as lattice structures, which allow bone in-growth and attachment. This section describes various requirements for such lattices (pore size, lattice design, etc.) in terms of bone growth and summarizes what has been achieved thus far. The following section describes the mechanical properties of titanium lattice structures of various types that have been produced by LPBF. The next two sections describe in detail successful in vitro and in vivo experiments, respectively, for bone growth on LPBF titanium alloys. Finally, a discussion section summarizes the current state of the art and highlights requirements for future research efforts.
关键词： Bone regeneration,Titanium alloys,Laser powder bed fusion,Additive manufacturing,Osseointegration
更新于2025-09-12 10:27:22
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Efficient Interfacial Solar Steam Generator with Controlled Macromorphology Derived from Flour via “Dough Figurine” Technology
摘要： Poor corrosion and wear resistance of magnesium (Mg) alloys restrict their applications. Herein, corrosion and wear-resistant films are formed upon Mg alloy AZ31 through a micro-arc oxidation (MAO) process in silicate electrolyte in the presence of carbon spheres (CS). Surface morphology, chemical composition, corrosion resistance, hardness, and coefficient of friction (CoF) of the MAO coatings are investigated using field-emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectrometry (FTIR), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), electrochemical and hydrogen evolution measurements, automatic micro-hardness testing, and reciprocating tribometer, respectively. Results demonstrate that the surface morphology and hardness of MAO coatings vary with the concentration of CS. The presence of CS results in an increased coating thickness from 8.0 (cid:1) 1.8 to 12.2 (cid:1) 1.8 μm, mean pore size from 0.7 (cid:1) 0.1 to 1.9 (cid:1) 0.1 μm, open porosity of MAO coating from 4.2 (cid:1) 0.4 to 5.6% (cid:1) 1.1%, and coating hardness from 347.0 (cid:1) 59.0 to 853.0 (cid:1) 67.3 Vickers-hardness (HV). Furthermore, CS-modified MAO coatings lead to improved corrosion resistance in comparison with that of the neat MAO counterparts. Moreover, the high hardness and formation of SiC of CS-modified coatings lead to a low and stabilized CoF, which implies an enhanced wear resistance.
关键词： micro-arc oxidation,coatings,corrosion resistance,carbon spheres,magnesium alloys
更新于2025-09-11 14:15:04
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In situ investigation of precipitation in aluminium alloys via thermal diffusivity from laser flash analysis
摘要： In this work, a commercially available laser flash analysis (LFA) device is used for in situ precipitation monitoring in aluminium alloys by following thermal diffusivity for the first time. The LFA measurement methods and data processing are adapted to allow continuous heating experiments over a wide range of heating rates (0.001–1 K s-1). Methods for LFA temperature calibration and thermal lag correction are suggested. Results of continuous heating of Al Mn0.5Mg0.5 aluminium alloy from the as-cast state are compared to in situ differential scanning calorimetry (DSC) and ex situ transmission electron microscopy. It is shown comparing in situ LFA, and DSC substantially improves the interpretation of superimposed reactions, in particular, the precipitation and dissolution of Mn-containing dispersoids and Mg–Si-containing secondary particles.
关键词： DSC,In situ LFA,Thermal diffusivity,Aluminium alloys,Precipitation,LFA thermal lag correction
更新于2025-09-11 14:15:04