Alloy Parts Research Articles

Effect of cyclic heat treatment on microstructure and tensile property of a laser powder-bed fusion-manufactured Ti–6Al–2Zr–1Mo–1V alloy

Laser powder-bed fusion (L-PBF) is increasingly being employed to fabricate titanium components for aerospace applications. However, L-PBF fabricated titanium alloy parts typically exhibit high strength but low ductility because of fine α′ martensite. Post-heat treatment is essential to compose α′ into stable α, thereby achieving improved ductility. In this study, we put forward a novel post-heat treatment, i.e., a cyclic treatment that included multiple cycles of low-to-high and high-to-low temperature annealing, to improve the ductility of an L-PBF fabricated Ti–6Al–2Zr–1Mo–1V (TA15) alloy. Its effect on the microstructures and tensile properties was investigated. The results showed that the as-fabricated TA15 alloy exhibited fine martensite, leading to high strength (i.e., an ultimate tensile strength of 1168 MPa) and low ductility (i.e., an elongation of 7.1 %). Conventional post-heat treatments introduced lamellar α+β structures and resulted in improved ductility of 9–13.9 % and reduced strength of 896–1070 MPa. The cyclic multistep treatment created trimodal structures of α-laths, equiaxed α, and thin film β. Especially, it contributed to the formation of up to 57 % equiaxed α grains compared to less than 5 % in the conventional treatments, leading to the enhanced ductility. This specific structure displayed superior properties, an ultimate tensile strength of ∼900 MPa, and elongation of ∼16 %, which are comparable to the TA15 alloy wrought counterparts. The optimized strength and ductility also demonstrated the potential of cyclic multistep treatment to enhance the performance of other additive manufactured titanium alloys.

Microstructure and mechanical properties of 7075 aluminum alloy parts formed by semi-solid thixoextrusion

Hot-extruded 7075 aluminum alloy was used to form deep cavity cylinders by thixoextrusion. The effects of isothermal temperature and soaking time on the microstructure and mechanical properties of the formed parts were analyzed. The parameters of T6 heat treatment were optimized by orthogonal test, and the influence of T6 heat treatment on the microstructure and mechanical properties of the formed parts was studied. The results indicated that the deep cavity cylinder with a smooth surface could be successfully formed through thixoextrusion. The forming temperature and heating time had remarkable effects on the metallographic structure of the formed components. T6 heat treatment could greatly enhance the mechanical properties of the deep cavity cylinders. The optimum parameters of T6 heat treatment were achieved as: solution at 465 °C for 16 h and aging at 150 °C for 16 h. When semi-solid billets were heated at 600 °C for 10 min, the formed deep cavity cylinder had the best mechanical properties with the ultimate tensile strength of 573.57 MPa, the elongation of 13.44%, and the microhardness of HV 187.12.

INVESTIGATION OF THE STRUCTURE AND PROPERTIES OF FERROUS NICKEL ALLOYS AFTER MOLDING BY SELECTIVE LASER MELTING

Problem statement. The selective laser melting method is a promising technology for the production of parts from heat-resistant alloys. Traditional methods of manufacturing such parts require additional technological equipment and processing, which increases the time of production preparation and, as a result, to the creation of a large number of raw materials. Selective laser melting allows you to produce parts of a complex configuration without the need for additional equipment. Molding of parts using additive technologies, which ensure a reduction in product preparation time, mechanical processing operations, and an increase in the efficiency of material use. Their application in the technological cycle of manufacturing products is an urgent task today. However, before the introduction into the technological process of forming products from heat-resistant alloys by the selective laser melting method, it is necessary to carry out a comprehensive analysis of the mechanical and technological characteristics of the material and its microstructure, which affects the final properties of the parts. The purpose of the article. Investigation of the possibility of implementing the selective laser melting method for the production of parts from strong alloys, analysis of the mechanical characteristics of the material, as well as the microstructure, which affects the final properties of the parts. Conclusions. Studies have shown that the selective laser melting method is effective for the production of complex parts from heat-resistant alloys. The obtained data on the mechanical properties after heat treatment of the Inconel718 alloy demonstrate its compliance with the requirements of the AMS 5662 standard and its suitability for working under extreme conditions. In the microstructure, highlighted features are revealed, which are characteristic of the selective laser melting method, as well as the presence of visible tracks and a special texture − elongated grains in the direction of growing parts. Research points to the potential of additive technologies in improving technological processes and properties of alloys for the production of heat-resistant alloy parts.

A Comparative Study on Microstructure, Segregation, and Mechanical Properties of Al-Si-Mg Alloy Parts Processed by GISS-HPDC and SEED-HPDC.

There are multiple routes to prepare semi-solid slurries with a globular microstructure for semi-solid forming. The variations in the microstructure of semi-solid slurries prepared using different routes may lead to significant differences in the flow behavior and mechanical properties of rheo-diecasting parts. Therefore, it is crucial to have a comprehensive understanding of the microstructure evolution associated with different slurry preparation routes and their resulting effects. In this study, the gas-induced semi-solid process (GISS) and the swirl enthalpy equilibrium device (SEED) routes were employed to prepare semi-solid Al-Si-Mg slurries for their simplicity and productivity in potential industrial applications. The prepared slurries were then injected into the shoot sleeves of a high-pressure die casting (HPDC) machine to produce tensile test bars. Subsequently, the bars underwent T6 treatment to enhance their mechanical properties. The microstructure, segregation, and mechanical properties of the samples were investigated and compared with those of conventional HPDC. The results indicated that the GISS and SEED can produce semi-solid slurries containing a spherical α-Al primary phase, as opposed to the dendritic structure commonly found in conventional castings. The liquid fraction had a significant effect on the flow behavior, resulting in variations in liquid segregation and mechanical properties. It was observed that a higher solid fraction (>75%) had a suppressing effect on surface liquid segregation. In addition, the tendency for liquid segregation gradually increased along the filling direction due to the special flow behavior of the semi-solid slurry with a low solid fraction. Furthermore, under the same die-casting process parameters, the conventional HPDC samples exhibit higher yield stress (139 ± 3 MPa) compared to SEED-HPDC and GISS-HPDC samples, which may be attributed to the small grain size and the distribution of eutectic phases. After undergoing the T6 treatment, both SEED-HPDC and GISS-HPDC samples showed a significant improvement in yield and tensile strength. These improvements are a result of solution and precipitation strengthening effects as well as the spheroidization of the eutectic Si phase. Moreover, the heat-treated SEED-HPDC samples demonstrate higher ultimate strength (336 ± 5 MPa) and elongation (13.7 ± 0.3%) in comparison to the GISS-HPDC samples (307 ± 4 MPa, 8.8 ± 0.2%) after heat treatment, mainly due to their low porosity density. These findings suggest that both GISS-HPDC and SEED-HPDC processes can be utilized to produce parts with favorable mechanical properties by implementing appropriate heat treatments. However, further investigation is required to control the porosities of GISS-HPDC samples during heat treatment.

Machine learning-enabled predictions of as-built relative density and high-cycle fatigue life of Ti6Al4V alloy additively manufactured by laser powder bed fusion

Ensuring high forming quality and performance of as-built components via laser powder bed fusion (LPBF) additive manufacturing (AM) necessitates, meticulous consideration of the material-process-structure-property relationships, particularly due to multiple interrelated AM process parameters exert complex non-linear effects on macro and micro-structures of as-built parts. The quest for optimal process parameters through iterative trial-and-error experiments incurs long time periods and substantial costs, while simultaneously suffering from a lack of precision in discerning the optimized parameters. To address these challenges, this study integrates machine learning (ML) and ML feature engineering techniques for predicting relative densities of LPBF-built Ti6Al4V alloy parts. The prediction performance of Bayesian network (BN) and Multilayer Perceptron (MLP) models are compared, concluding that the MLP prediction model has higher efficiency and accuracy. This prediction model can be inverted to derive optimized LPBF process parameters based on desired density values. The influences of AM defects characterized by micro-computed tomography (μ-CT) on high-cycle fatigue life of LPBF-built Ti6Al4V alloy was studied, for establishing a ML-based pathway for predicting the fatigue life with another MLP model. The efficient approaches offer valuable insights into developing high-precision and widely applicable mapping models that encompass the interplay between process, defects, and fatigue life.

Improvement of microstructure and mechanical properties of TC4 titanium alloy GTAW based wire arc additive manufacturing by using interpass milling

TC4 titanium alloy wire arc additive manufacturing (WAAM) is easy to produce coarse columnar β grain structure which affects mechanical properties. So in this paper, an innovative process of interpass milling assisted TC4 titanium alloy gas tungsten arc welding (GTAW) WAAM is proposed. The controlling interpass milling depth is used to improve the microstructure and mechanical properties of TC4 titanium alloy parts during the GTAW-WAAM. The results showed that the coarse columnar β grains and fine α phase were observed in the non-interpass milling part. When the interpass milling assistance GTAW-WAAM was employed, the coarse columnar β grains transformed into short columnar and equiaxed grains. With the increased of interpass milling depth, the average size of α phase was gradually refined to 13.5 μm below. The highest average microhardness in the top, middle and bottom areas obtained by using the interpass milling depth of 300 μm were 369 HV0.2, 371 HV0.2 and 371 HV0.2 respectively, which was increased by 32 HV0.2, 28 HV0.2 and 26 HV0.2 compared with non-interpass milling respectively. The horizontal and vertical ultimate tensile strength first increases and then decreases with the increase of interpass milling depth, reaching its maximum at a milling depth of 300 μm. The highest tensile strength of the horizontal and vertical directions obtained by using the interpass milling depth of 300 μm were 1022 MPa and 1042 MPa. The level of the ultimate tensile strength is related to the combined proportion of total average β grain size and total average < 15 μm α phase size, and the proportion of both is balanced and maximized to obtain the maximum ultimate tensile strength. The interpass milling depth of 300 μm satisfies both conditions, so its maximum horizontal and vertical ultimate tensile strength is achieved. Fracture type of tensile specimen was ductile fracture due to observing a lot of dimples on the fracture morphology. The above conclusions show that interpass milling is an aided process to effectively improve the microstructure and mechanical properties of TC4 titanium alloy GTAW wire arc additive manufacturing thin-walled parts, which has high research significance and practical value.

Аналіз розвитку термоімпульсного методу видалення задирок

The subject of study in this article is theoretical and experimental studies of the process of removing burrs in the details obtained by metalworking using the thermopulse method of combustion of detonating gas mixtures. The purpose of this article is to substantiate the use of the thermopulse method for finishing parts, which was developed at Kharkiv Aviation Institute in the early 70s of the 20th century for the flexible automation of cleaning the surfaces and edges of parts of hydraulic and fuel units of aviation and rocket-space equipment from burrs and technological contamination. The task was to determine the features of the thermal pulse method, the parameters of the technological process from the viewpoint of its application for processing the edges of parts with complex internal and external surfaces, and to reveal its potential for use in precision engineering. The research methods used are the modeling of processes using the finite element method and an experimental method for checking the adequacy of the proposed numerical models. The following results were obtained: processing of parts made of materials with different thermal conductivities, cleaning of rubber products, and rounding of the edges of threaded holes of aluminum alloy parts by melting. The scientific and practical novelty of the obtained results is as follows: the technological possibilities of thermopulse processing, justified control parameters, and optimization of processing modes are given; to consider the processes of heating the elements of the part and the combustion of detonating mixtures in the working chamber of the equipment; obtained regularities of changes in the temperature fields of liquids and structural elements of parts during pulsed, constant, and mixed heating, which make it possible to form regimes of thermopulse processing of parts considering their structural features in several thermophysical properties of materials; developed processes of thermal pulse removal of burrs, microparticles, and dimensional rounding of edges using the results of modeling and experimental refinement on T-15 installations.

Defects control of aluminum alloys and their composites fabricated via laser powder bed fusion: A review

Laser powder bed fusion (L-PBF) technique, as the mainstream technology in metal additive manufacturing, enables the fabrication of aluminum alloys and their composite components with high precision and design freedom, thereby advancing structural lightweighting in various application domains, such as aerospace and transportation. Nevertheless, aluminum powders present challenges including high laser reflectivity, high thermal conductivity, low melting point, and susceptibility to oxidation. Consequently, defects such as pores, solidification cracks, orientation anisotropy, and surface roughness commonly exist in L-PBFed aluminum alloy and composite parts. These defects severely compromise the mechanical performance and dimensional accuracy of L-PBFed parts. Thus, extensive research efforts have been focused on defect control in the L-PBFed aluminum alloys and their composites. However, a systematic summary and in-depth analysis of the formation mechanism and controlling strategy of various defects is still absent, which is the key to develop high performance aluminum alloys and their composites via L-PBF. In this review, a thorough analysis and summary of the causes of defects are provided, followed by an in-depth analysis and conclusion of defect control strategies and mechanism in L-PBF. Furthermore, we also present an outlook on the challenges and research opportunities in L-PBFed aluminum alloys and their composites in the last section, which we hope could inspire more new development of high-performance aluminum alloys and their composites via L-PBF.

Material Health of NiCrBSi Alloy Parts Produced via the Laser Powder Bed Fusion Process

Laser powder bed fusion (L-PBF) is a novel process representing a possible solution for producing resistant parts using NiCrBSi hard-facing nickel alloys with complex geometry. Process parameters for more common alloys are explored with a standard Renishaw AM400 device (Renishaw, Wotton-under-Edge, UK) and an SLM Solution 250 device (SLM Solutions Group AG, Lübeck, Germany) modified with a baseplate preheated at high temperatures (300 °C and 500 °C). Laser remelting is also investigated in hopes of further improving material health. The origin of the main defects is studied. A lack of fusion is likely to be generated by spatters ejected from the melting pool while cracks are induced by the alloy’s lack of toughness. Using image analyses, those defects are quantified and correlated with processing parameters. Lack of fusion and total crack length decrease with an increase in baseplate’s preheating temperature. However, crack width increases with preheating temperature. Therefore, via a careful optimization of process parameters, samples with a surface density of 99% and narrow cracks are obtained.

Mechanisms of macrozone elimination and grain refinement of near α Ti alloy via the spheroidization of the Widmannstätten structure

Regions with sharp local textures, i.e., macrozones, are common microstructural inhomogeneities in titanium (Ti) alloys that significantly reduce the fatigue resistance of Ti alloy parts. In this study, a two-stage thermomechanical operation was developed to eliminate macrozones and optimize microstructure in a near α Ti alloy. Multiscale microstructure characterization and full-field crystal plasticity (CP) modeling were conducted to uncover the underlying mechanisms. Spheroidizing through dynamic recrystallization (DRX) and superplasticity are indispensable ingredients. The alloy exhibited multiple DRX phenomena, which are strongly associated with grain morphologies. The discontinuous DRX and the main spheroidizing mechanism of the equiaxed primary α phase failed to eliminate macrozones but exacerbated microstructure heterogeneities due to the strong anisotropy of the hexagonal close-packed α phase. The Widmannstätten structure (WS), fabricated through the β heat treatment that generated abundant nano-defects and serrated grain boundaries, significantly promoted the occurrence of geometric dynamic recrystallization (GDRX). A complete GDRX of lamellar α grains can generate a sufficiently fine-grain structure to achieve superplastic deformation in the subsequent hot compression at a moderate deformation. The full-field CP simulations considering slip only versus slip + superplasticity confirmed that the dislocation slip dominated deformation aggravated deformation heterogeneity and the formation of macrozones. In contrast, the superplastic deformation suppressed the heterogeneous deformation and randomized the grain rotation, which in turn homogenized the microstructure and eliminated macrozones. Based on these observations, the β heat treatment followed by α hot compression is an effective method to achieve grain refinement and macrozone elimination of Ti alloys.

Effect of Oxygen Content on Microstructure and Mechanical Properties of Additive Manufactured Ti-6Al-4V

Titanium alloys are used in many fields including military, aerospace, and biomedical because of their excellent specific strength, corrosion resistance, and biocompatibility. Recently, much research has been focused on addressing the disadvantages of conventional manufacturing methods, including reducing material and energy waste when manufacturing titanium alloy parts by additive manufacturing methods. However, due to rapid cooling, during the additive manufacturing process the material develops acicular and lamellar microstructures, and despite high strength, those features are detrimental to ductility and toughness, as compared with conventionally manufactured alloys. As a result, numerous studies have sought to obtain an equiaxed microstructure through heat treatment. However, the developed heat treatment processes are quite complex, and involve several heat treatment cycles, making such processes economically unfavorable. To overcome these limitations we suggest a different approach to obtaining an equiaxed structure in 3D-printed titanium alloy, by controlling the oxygen level. The present study analyzed the globularization behavior of Direct Energy Deposited (DED) Ti-6Al-4V alloy as a function of oxygen content and a simple heat treatment. The microstructure was globularized through oxygen level control and furnace cooling to compensate the disadvantages in the mechanical properties of additive manufactured alloys.

Speed function effects on properties of Ti-5Al-5Mo-5 V-1Cr-1Fe alloy manufactured by electron beam melting

The speed function (SF) parameter, which is a unique combination of beam speed and beam current, is one of the most important parameters of the electron beam melting (PBF-EB) production process. It allows the same process conditions (size of the melt pool, process temperature, etc.) to be maintained for parts with different geometries and sizes. The aim of this research was to understand the effect of SF on the Ti-5Al-5Mo-5V-1Cr-1Fe alloy produced by electron beam melting technology. The results showed that increasing the SF from 86 to 116 resulted in a decrease in the average process temperature, a decrease in the length of the α phase plates, and change in the proportion of α and β phases from 53% (SF 86) to 50% (SF 116) of the β phases. Differences in microstructure (column diameters, thickness, and length of α-phase plates), phase composition, microhardness, porosity at the bottom, and top of the samples were observed on all samples. The mechanical property analysis did not show a significant effect of SF on elongation, but an increase in SF from 86 to 96 resulted in an increase in ultimate tensile strength (UTS) of approximately 7%, whilst an additional increase to 116 resulted in a decrease in UTS of approximately 8.5% compared to SF 96. From the results, it can be seen that the microstructural and mechanical properties of the material strongly depend on the SF. Based on it, SF 86 can be considered as the recommended value for the manufacture of Ti-55511 alloy parts.

Wire arc additive manufacturing of a novel ATZM31 Mg alloy: Microstructure evolution and mechanical properties

The preparation of large-scale magnesium (Mg) alloy parts by wire arc additive manufacturing (WAAM) has broad application prospects, including automotive and aerospace industries. The chemical composition of Mg alloy wires plays a critical role in determining mechanical properties of WAAM Mg alloys. However, types of Mg alloy wires for WAAM need to be extended, in order to improve mechanical properties. Therefore, in the present work, a novel ATZM31 Mg alloy wire has been prepared and applied to the cold metal transfer (CMT)-WAAM process. This study focuses on understanding the forming quality, microstructure evolution, and mechanical properties of the ATZM31 alloy thin-wall component fabricated by WAAM. The results show that the Mg alloy thin-wall component possesses satisfactory formability, with minor sidewall roughness. The ATZM31 thin-wall component is mainly composed of columnar dendrites and equiaxed dendrites of the α-Mg phase, with the η-Al8Mn5 phase distributes dispersedly at grain boundaries. The area fraction of the η-Al8Mn5 phase is estimated to be ∼0.21% based on the statistical analysis of SEM images. Due to different cooling behaviors, the distribution of grain size along the build direction of the thin-walled component is uneven. The average grain size is ∼46 µm, ∼74 µm and ∼61 µm at the bottom, middle and top of the ATZM31 alloy thin-wall component, respectively. From the substrate to the top of the ATZM31 alloy thin-wall component, the hardness decreases gradually. The ultimate tensile strength along the deposition direction and build direction are ∼225 MPa and ∼214 MPa, respectively, without pronounced anisotropy. The ATZM31 alloy thin-wall component fabricated by WAAM exhibits a comparable ultimate tensile strength to forged AZ31 Mg alloys and weaker anisotropy than wrought Mg alloys.

Numerical study on melt pool characteristics of thin-walled parts deposited by laser of IN718 alloy

As an efficient near-net shape-forming technology, LMD has attracted much attention. In this paper, the LMD process of single-pass multi-layer thin-walled parts of the nickel-based alloy is simulated by the finite element method, and the characteristic parameters of the melt pool are studied according to the temperature field. The impact of the process parameters including scan speed, laser power, spot radius as well as deposition thickness on the melt pool volume is discussed, which aims to provide theoretical support for the AM.

Optimized bilateral ultrasonic surface rolling process assisting directed energy deposition of thin-walled medium-entropy alloy with high mechanical performance

Laser directed energy deposition (DED) offers significant advantages for the integral manufacturing of large-scaled thin-walled workpieces. Nevertheless, how to improve the yield strength (YS) and fatigue properties of thin-walled parts fabricated by DED is a crucial issue. As an advanced surface strengthening technology, ultrasonic surface rolling process (USRP) is aimed to improve the mechanical performances of additively manufactured workpieces. In this work, an optimized bilateral USRP parameter (including the load, repeated times, scanning speed, etc.) with high manufacturing efficiency and surface integrity was developed to fabricate thin-walled CoCrNi medium-entropy alloy (MEA) parts (~1.5mm thickness). Compared to the as-deposited sample, the sample treated by USRP shows a good strength-ductility balance (ultra-high YS and ductility with 1026.6MPa and 21.9%, respectively), as well as an impressive improvement in the high-cycle fatigue limit strength of 76.9%. The reasons for high mechanical performance are revealed through multi-scale characterization and calculation. Ultra-high strength is predominantly attributed to the high-density pre-existing dislocations and deformation twins (DTs); Good ductility is related with high hetero-deformation induced stress and the activation of multiple deformation substructures induced by high flow stress, such as dislocations, DTs and hexagonal close-packed phase. Further, the improvement in fatigue performance is ascribed to the closure of manufacturing defects in the surface or subsurface and inhibited surface roughening behavior from stable gradient nanotwinned layer. Finally, the work reveals the quantitative relationship among processing-properties-promotion mechanism (PPP), which provides a criterion to meet the specific mechanical performance of DEDed thin-walled components by precisely tuning the bilateral USRP parameters.

Enhanced Mechanical Properties of QAl9-4 Aluminum Bronze for High-Speed-Rail Brake Systems with a Pulsed Magnetic Field.

To improve the mechanical properties and wear resistance of QAl9-4 aluminum bronze alloy parts of high-speed rail brake calipers, the solid aluminum bronze alloy was treated with a pulsed magnetic field in which the magnetic induction intensity was 3T at room temperature. After that, a tensile test and a friction and wear test were carried out on the alloy. The results indicate that the magnetic field promotes the movement of low-angle grain boundaries less than 2° and splices to form subcrystals or fine crystals, which reduces the mean grain size of the alloy. The disordered dislocation changed into a locally ordered dislocation line, the dislocation distribution became uniform, and the dislocation density increased, which simultaneously improved the alloy's tensile strength and elongation. The elongation increased by 10.2% compared with that without the magnetic field. The increase in strength can provide strong support for the wear-resistant hard phase, and the enhancement of plasticity can increase the alloy's ability to absorb frictional vibration. Therefore, it was hard for cracks to form and extend, and the specimen's average friction coefficient was reduced by 22.05%. The grinding crack width and depth decreased, the wear debris became more uniform and fine, and the alloy's wear resistance increased.

Influence of Welding Tool Geometry on the SFSW Joint Dimensions of the EN AW 1200 Aluminium Alloy

The aim of the present paper is to study the aspects regarding the influence of the welding tool geometry on the joint dimensions during the SFSW (Submerged Friction-Stir Welding) of the EN AW 1200 aluminium alloy. Different tool geometries for SFSW welding of EN AW 1200 aluminium alloy parts were used, and joint size was analysed by macrostructural investigations. The key characteristics of the tool-weld interaction can be extracted, analysed and summarized to provide guidance on the optimal tool selection for a given set of welding conditions.

Rheological Modeling of 7075 Aluminum Alloy Semi-Solid Slurry and its Application in the Simulation of SEED Rheocasting Process

Rheocasting technology has been successfully applied to produce aluminum alloy parts of automobile and communication equipment. However, its application scope is still limited. One reason is that the strength of the applied alloys is limited. In recent years, lots of researchers have tried to use 7075 aluminum alloy in the rheocasting process because this alloy has excellent mechanical properties. In this work, the rheological behavior of 7075 aluminum alloy semi-solid slurry is studied through shear stress-controlled test and shear rate-controlled test. Then the constitutive parameters in Power-Law (PL) model or Carreau-Yasuda (CY) model of non-Newtonian fluid are determined. The models are used to simulate the flow behavior of 7075 aluminum alloy semi-solid slurry in Swirled Enthalpy Equilibration Device (SEED) rheocasting process. The simulation results indicate that the CY model derived from the shear rate sweep test is more suitable for simulating the flow behavior of 7075 aluminum alloy semi-solid slurry during rheocasting than the other models.

Influence of carbon nanoparticle inoculation on the structure of ML5 casting magnesium alloy

The object of this study is to investigate the structure of cast magnesium alloy (Mg-Al-Zn) inoculated with nano particles of different allotropic forms of carbon. The aim of this study is to improve the processability and quality of critical load bearing magnesium alloy part castings. The tasks of the study are: attainment of efficient control of the alloy structural features by introduction of incremental additions of carbon nano particles; determination of the relationship between the quantity of the added inoculating carbon agent and α - solid solution grain size; determination of the influence of allotropic forms of carbon on the morphologic characteristics of the intergranular borders and the eutectoid (a+Mg17Al12); and comparative analysis of the phase composition of the standard ML5 alloy and the experimental alloy ML5 inoculated with carbon black, nanographite, and single-wall carbon nanotubes. The phase composition was determined by X-ray diffraction analysis using copper radiation. Micro X-ray spectral analysis was performed. The following findings were obtained. Using an optical microscope α – solid solution grain size was measured in the standard and inoculated alloy. In the samples of the alloy variants inoculated with 0.1 % wt. of carbon black, nanographite, and single-wall carbon nanotubes, the grain size was reduced by appox. 50 % compared with the standard alloy. In the samples of the alloy inoculated with 0.1 % wt. of nanographite and single wall carbon nanotubes, eutectoid (a+Mg17Al12) precipitates along the grain boundaries were thinner than those in the standard alloy samples and those inoculated with carbon black. X-ray diffraction analysis revealed no new phase formation. The X-ray diffraction patterns of the alloy samples with nanographite and nanotubes display weak peaks of free carbon, which may indicate the presence of free carbon in small quantities in the structure. The scientific and practical originality of the obtained results consists of the following: a technology of inoculation with incremental additions of allotropic forms of nano carbon, namely carbon black, nanographite, and single-wall carbon nanotubes, has been tested on a standard cast magnesium alloy (Mg-Al-Zn system) in an environment similar to the industrial production of critical magnesium cast components. It has been shown that the introduction of nanocarbon in a quantity of 0.1 % wt. can have a beneficial effect on the structural characteristics of ML5 cast magnesium alloy with no change in its phase composition. Nanographite and single wall carbon nanotubes with a regular structure contribute to the formation of thinner intergranular boundaries than amorphous carbon black.

A synergistic impact of LPBF process parameters on attaining a defect-free Cu-Cr-Zr alloy parts: an analytical and experimental study

A synergistic impact of LPBF process parameters on attaining a defect-free Cu-Cr-Zr alloy parts: an analytical and experimental study