https://mater-tehnol.si/index.php/MatTech/issue/feed Materials and Technology 2022-04-11T11:04:19+02:00 Roman Celin mit@imt.si Open Journal Systems <div class="article"> <div class="article"> <p>The journal Materiali in tehnologije / Materials and Technology is a scientific journal, devoted to original scientific papers concerned with the areas of fundamental and applied science and technology. Topics of particular interest include metallic materials, inorganic materials, polymers, vacuum techniques, nanomaterials and lately biomaterials.<br>© MATERIALI IN TEHNOLOGIJE<br><br><strong>Published by:</strong><br>Institute of Metals and Technology, Lepi pot 11, 1000 Ljubljana, Slovenia</p> <p><br><strong>Associated publishers:</strong><br>IMPOL Slovenska Bistrica, Slovenia • METAL Ravne, Slovenia • TALUM Kidričevo, Slovenia<br><br>Materiali in tehnologije / Materials and Technology journal is financially supported by Slovenian Research Agency (ARRS).</p> </div> </div> https://mater-tehnol.si/index.php/MatTech/article/view/331 HOT-COMPRESSION DEFORMATION BEHAVIOR AND CONSTITUTIVE EQUATIONS OF LZ50 AXLE STEEL 2022-04-05T12:30:43+02:00 Dongsheng Jia jiadongshengyx@163.com Tao He hetao@sues.edu.cn Yuan-ming Huo hetao@sues.edu.cn Xiang-yang Du hetao@sues.edu.cn Bao-yu Wang hetao@sues.edu.cn Shi-qian Li hetao@sues.edu.cn Han-lin Li hetao@sues.edu.cn <p>A study of deformation behavior of LZ50 axle steel has great significance to the railway industry. Hot-deformation tests were performed using a Gleeble-3800 thermal mechanical simulator at temperatures of (900, 1000 and 1100) °C with strain rates of (0.1, 1.0 and 10.0) s<sup>–1</sup> under different deformation degrees of 0.2, 0.6 and 1.0. True stress-strain curves were discussed to obtain hot-processing maps. Then hot-processing maps of LZ50 steel at different deformation parameters were discussed including safe zones and unsafe zones. Finally, thermal deformation constitutive equations and dynamic recrystallization models were established based on the experimental data. The results show that at a strain rate of 10.0 s<sup>–1</sup>, the peak value of the flow stress increases by approximately 40 MPa with a decrease in the temperature from 1000 °C 900 °C, which is larger than the value of 18&nbsp;MPa obtained at a decrease from 1100 °C to 1000 °C. At deformation temperatures of 900–1000 °C, the peak value of the flow stress increases by approximately 37 MPa with the strain rate increasing from 0.1 s<sup>–1</sup> to 1.0 s<sup>–1</sup>, while from 1.0 s<sup>–1</sup> to 10.0&nbsp;s<sup>–1</sup>, the increase is approximately 21 MPa. With an increase in the strain from 0.2 to 1.0, the instability area under the low deformation temperature expands due to a higher strain rate. The activation energy of dynamic recrystallization is 334.537&nbsp;kJ/mol.</p> 2022-04-06T00:00:00+02:00 Copyright (c) 2022 Materials and Technology https://mater-tehnol.si/index.php/MatTech/article/view/353 WHITE-LAYER THICKNESS ON EDM-PROCESSED AISI A2 STEEL – MATHEMATICAL MODELING AND ANALYSIS 2022-04-05T12:30:44+02:00 Dinesh Kumar dineshmmm@gmail.com Krishan Kant Singh Mer kks.mer2008@gmail.com Hoshiyar Singh Payal 14payal.hs@gmail.com Kapil Kumar chauhankumarkapil@gmail.com <p>Electrical discharge machining is an electro-thermal technique where the recast layer on a machined surface and the heat-affected zone (HAZ) immediately below the machined surface are prevalent. As a result, assessing the white layer (recast layer) in EDM is a critical task. In this research, a response-surface methodology-based comprehensive mathematical model was developed to predict the white-layer thickness (WLT) on electrical discharge machine-processed AISI A2 steel. Also, the effects of various process parameters on the WLT were presented, the optimum combination of process variables was assessed and the minimum WLT was achieved by combining low-peak current and pulse-on time with high pulse-off time.</p> 2022-04-06T00:00:00+02:00 Copyright (c) 2022 Materials and Technology https://mater-tehnol.si/index.php/MatTech/article/view/364 NUMERICAL AND EXPERIMENTAL INVESTIGATIONS ON GFRP AND AA 6061 LAMINATE COMPOSITES FOR DEEP-DRAWING APPLICATIONS 2022-04-05T12:30:44+02:00 Kavitha Kalidass kavitharaj31@gmail.com Vijayan Raghavan kavitharaj31@gmail.com <p>Fibre-metal laminates (FMLs) are a multi-layered prominent class of hybrid composites gaining keen attention among researchers due to the combined advantages of the products used for aerospace and lightweight applications. This work involves one such investigation of hybrid sandwich laminate composites of aluminium sheets and a glass-fibre-reinforced thermoplastic (GFRP) core. FRPs can be conjoined with other lightweight materials to enhance the weight-to-strength forming performance and reduce manufacturing costs. However, the thickness reduction of the components for lightweight products makes the FRP-to-metal amalgamation a great challenge. The process of warm embossing is imposed to enhance the quality of single-lap adhesive bonding in FRPs and AA 6061 thin sheets. In this investigation, the formability of a FML made of AA 6061 and GFRP is predicted based on its deformation and wrinkle formation when it is processed during deep drawing. This research paper deals with analytical and experimental results regarding the prediction of deformation cause and effect in fabricated composite laminates with orientation angles of (90°; 0°; 60°; 30°; –45°; 45°). The method of evaluation combines the usage of ANSYS PrepPost with an explicit-dynamics module that bolsters designing, drafting and analysis.</p> 2022-04-06T00:00:00+02:00 Copyright (c) 2022 Materials and Technology https://mater-tehnol.si/index.php/MatTech/article/view/365 CHARACTERIZATION OF HYBRID ALUMINUM COMPOSITES REINFORCED WITH Al2O3 PARTICLES AND WALNUT-SHELL ASH 2022-04-05T12:30:45+02:00 Jasmina Petrović jpetrovic@tfbor.bg.ac.rs Srba Mladenović smladenovic@tfbor.bg.ac.rs Ivana Marković imarkovic@tfbor.bg.ac.rs Silvana Dimitrijević silvana.dimitrijevic@irmbor.co.rs <p>Hybrid aluminum composites obtained with stir casting were investigated in this study. Aluminum alloy EN AW 6061 was reinforced with particles of Al<sub>2</sub>O<sub>3</sub> and walnut-shell ash (WSA). The weight fraction of Al<sub>2</sub>O<sub>3 </sub>was constant (5 <em>w</em>/%) and for the walnut-shell ash, it was (1, 2 and 3) <em>w</em>/%. The morphology of the composites and particle distribution were examined with an optical microscope and scanning electron microscope. Microstructural studies showed a uniform distribution of the reinforced particles in all the investigated samples. A chemical analysis of the reinforcing particles on the samples’ surfaces was done using an energy-dispersive spectrometer. The changes in the mechanical properties including the hardness, tensile strength and elongation in relation to the increase in the weight fraction of ash were investigated. The results showed that the hardness and tensile strength increase, while the elongation decreases with an increase in the weight fraction of ash in the composites. The mechanical properties of the obtained composites showed improvement compared to the EN AW 6061 alloy.</p> 2022-04-06T00:00:00+02:00 Copyright (c) 2022 Materials and Technology https://mater-tehnol.si/index.php/MatTech/article/view/340 INFLUENCE OF VOLTAGE AND CURRENT ON THE ARC SHAPE IN CABLE-TYPE WIRE TIG-MIG HYBRID WELDING 2022-04-05T12:30:45+02:00 Qingxian Hu 18761183263@sina.com Chao Zhang huqingxian@just.edu.cn <p>In order to achieve high efficiency, energy saving and high quality of welding, it is necessary to carry out research on cable-type wire TIG-MIG hybrid welding. In this study, voltage and current influences on the arc shape in cable-type wire TIG-MIG hybrid welding were studied. The results showed that in cable-type wire TIG-MIG hybrid welding, with an increase in the TIG current, the MIG current increased at first and then remained constant, while the MIG basic voltage remained unchanged. With an increase in the MIG voltage, the TIG current produced small changes, but overall, it remained stable. The TIG current of different droplet-transfer modes had different effects.</p> 2022-04-06T00:00:00+02:00 Copyright (c) 2022 Materials and Technology https://mater-tehnol.si/index.php/MatTech/article/view/368 EXPERIMENTAL INVESTIGATION OF ELECTRICAL DISCHARGE MACHINING OF INCONEL 718 USING A TiB2-Cu SINTERED COMPOSITE ELECTRODE 2022-04-05T12:30:46+02:00 P. Mathan Kumar mathan129@gmail.com K. Sivakumar mathan129@gmail.com S. M. Vinu Kumar mathan129@gmail.com <p>Electrical discharge machining (EDM) is much preferred in modern precision-manufacturing industries owing to its ability to machine any metal regardless of its hardness. However, its constraint is that the selected metal should be an electrically conductive material. For the present investigation, an Inconel 718 alloy was selected for EDM, using a TiB<sub>2</sub>-Cu electrode made with powder metallurgy. Input factors, namely, the pulse current (<em>I</em><sub>p</sub>), pulse-on time (<em>T</em><sub>on</sub>) and gap voltage (<em>G</em><sub>v</sub>) were selected and their output responses were the surface roughness (SR) and material-removal rate (MRR). For the response surface, the Box Behnken technique was preferred when designing the experiments (DoE). An ANOVA test was performed to understand the influence of the selected input factors on the SR and MRR. The RSM integrated with a grey relational analysis (GRA) revealed that the optimal input parameters for better machining characteristics were: <em>I</em><sub>p</sub> = 10 A, <em>T</em><sub>on</sub> = 40 µs and <em>G</em><sub>v</sub> = 50 V. Besides, the results also showed that the pulse current more significantly influenced the output responses than the other parameters. Moreover, an increase in the gap voltage caused surface irregularities on the machined surface. Surface morphology of the machined surfaces was analysed through SEM and EDAX. Moreover, a certain amount of tool-material transfer was noted with the EDAX analysis.</p> 2022-04-06T00:00:00+02:00 Copyright (c) 2022 Materials and Technology https://mater-tehnol.si/index.php/MatTech/article/view/354 MICROSTRUCTURE EVOLUTION AND CORROSION BEHAVIOR OF Al-Si/Al-Mn COMPOSITES IN SALT SPRAY 2022-04-05T12:30:46+02:00 Zhifeng Li li.zhifeng@csu.edu.cn <p>Al-Si/Al-Mn composites are commonly used in aluminum heat exchangers. Improving their corrosion resistance is the key for prolonging their service life and reducing their costs. In this paper, an artificial salt spray corrosion test was adopted in accordance with the ASTM G85 standard to evaluate the atmospheric corrosion resistance of Al-Si/Al-Mn composites. The corroded samples were tested with electrochemical impedance spectroscopy (EIS). Microstructure evolution and their corrosion mechanism were discussed after the use of OM, SEM, EPMA and XRD. The results showed two corrosion mechanisms, including the pitting-induction mechanism and intergranular-development mechanism: pitting is induced by the destruction of the passive film as Cl<sup>–</sup> is adsorbed at the defects, while the corrosive medium in the pitting pores expands along the grain boundaries where eutectic Si is enriched. A corrosion process can be divided into three periods: the pitting-induction period, pitting-propagation period and matrix-corrosion period. The equivalent circuit models established sequentially were consistent with the actual macroscopic and microscopic observations.</p> 2022-04-06T00:00:00+02:00 Copyright (c) 2022 Materials and Technology https://mater-tehnol.si/index.php/MatTech/article/view/377 STRUCTURAL AND ELASTIC PROPERTIES OF AgNi10 ALLOY STUDIED WITH AB-INITIO CALCULATIONS 2022-04-05T12:30:47+02:00 Jide Liu jdliu@imr.ac.cn Xue Wang 26459874@qq.com Xaoming Du du511@163.com Ming Xie du511@163.com Jinguo Li du511@163.com Shangqiang Zhao du511@163.com Yizhou Zhou du511@163.com Qiao Zhang du511@163.com Jiheng Fang du511@163.com <p>First-principles calculations based on density functional theory (DFT) are used to calculate the structural, elastic and thermodynamic properties of the supersaturated solid-solution AgNi<sub>10</sub> alloy, applied mainly to electrical contact materials. In this work, for the exchange-correlation energy, the generalized gradient approximation (GGA) functional is used. The calculated structural and electronic properties of supersaturated solid-solution AgNi<sub>10</sub> alloys show that the occupation of Ni in the Ag lattice is ordered. All single-crystal elastic stiffness constants of the energetically and mechanically optimized stable AgNi<sub>10</sub> model are calculated using the finite strain method and using the Voigt-Reuss-Hill approximation. Various anisotropic indices like the universal anisotropic index, shear anisotropic index, directional dependence of Young’s modulus, bulk modulus and others are calculated to study the elastic anisotropy. The strong anisotropy in the elastic properties of AgNi<sub>10</sub> was confirmed. Phonon dispersions were carried out, showing that the AgNi<sub>10</sub> crystal has dynamic stability. The Debye temperature is calculated from the elastic data by estimating the average sound velocity in the AgNi<sub>10</sub>. Furthermore, the vibrational thermodynamic properties (free energy, enthalpy, entropy and heat capacity) of AgNi<sub>10</sub> are obtained successfully.</p> 2022-04-06T00:00:00+02:00 Copyright (c) 2022 Materials and Technology https://mater-tehnol.si/index.php/MatTech/article/view/196 INFLUENCE OF TEMPERATURE EFFECTS ON NANO-SILICA BLENDED SELF-COMPACTING GLASS MORTAR 2022-04-05T12:30:47+02:00 Ganesh Babu O sakthistructrichy@gmail.com Sakthieswaran N sakthistructrichy@gmail.com Muthuraman U sakthistructrichy@gmail.com Suresh P sakthistructrichy@gmail.com <p>Self-compacting mortars are achieving a great deal in the construction industry due to their remarkable characteristics and due to their advantages over conventional concrete. The main drawback associated with self-compacting mortars is the high cost associated with the ingredients used in the production of self-compacting mortars. This research aims to overcome this by combining the effects of nano-silica and glass powder on the properties of self-compacting mortar at normal and higher temperatures. The experiments were conducted to determine the split tensile strength over a range of curing periods and after being subjected to various temperatures. Durability properties of the self-compacting glass mortar, such as sorptivity, were also studied and compared with the properties of the control mortar. In addition, the chloride penetration resistance of the self-compacting mortars were also studied. The microstructure properties, such as X-ray diffraction and FTIR studies, were also performed to analyze the characteristics of self-compacting glass mortars at the micro level. The proposed mortar design can solve the problem of the disposal of waste glass, prevent the the depletion of natural river aggregates and also prove to be cost effective for massive construction purposes.</p> 2022-04-06T00:00:00+02:00 Copyright (c) 2022 Materials and Technology https://mater-tehnol.si/index.php/MatTech/article/view/352 ADSORPTION OF LEAD FROM CONTAMINATED WATER USING BIOSORBENT 2022-04-05T12:30:48+02:00 J. Prakash Arul Jose prakasharuljosej@gmail.com M. Dharsana prakasharuljosej@gmail.com <p>For the past few years, environmental degradation caused by the discharge of heavy metals and organic contaminants has been a major source of worry. Using a natural adsorbent to tackle wastewater problems has recently been viewed as an environmentally friendly move that promotes sustainable development. Heavy metals have indeed been reduced in aqueous solutions using a variety of methods, include adsorption to the surfaces of agricultural residues. Lead is among the most toxic and common heavy metals found in industrial wastewater. In this research, adsorbents selected are moringa leaves, rice husk and coconut fibers, which are very low-cost materials, employed for the lead exclusion from industrial wastes. Thus, our study aims to investigate the ability of natural bio-sorbents to remove very toxic Pb<sup>2+</sup> ions from aqueous solutions. Contact time, concentration, adsorbent-based dosage and pH were all evaluated as important factors in the adsorption mechanism. The adsorption efficiency was discovered to be pH dependent, rising as the solution pH was increased in the ranges of 2.5 to 6.5. After 120 min, the equilibrium state was reached, and the optimum removal rate was obtained with a 1.5 g adsorbent loaded weight. The adsorption equilibrium capability of the lead-adsorbing materials was evaluated and estimated utilizing linear Freundlich and Langmuir isotherms, with the experimental results fitting the Freundlich isotherm models.</p> 2022-04-06T00:00:00+02:00 Copyright (c) 2022 Materials and Technology https://mater-tehnol.si/index.php/MatTech/article/view/397 ANALYSIS OF A CRYOGENICALLY COOLED NEAR-DRY WEDM PROCESS USING DIFFERENT DIELECTRICS 2022-04-07T13:27:49+02:00 K. Gunasekaran boopasangee@gmail.com Sampath Boopathi boopasangee@gmail.com M. Sureshkumar boopasangee@gmail.com <p>In this research, a cryogenically cooled, near-dry, wire-cut, electrical discharge machining (CNDWEDM) investigation was performed using air, oxygen, and helium gases mixed with the minimum quantity of dielectric water as the working medium to cut Inconel-718 alloy with a molybdenum wire tool. All the experiments have been performed using the –150 °C temperature of the liquid-nitrogen-cooled wire electrode. The comparative analysis of the wire wear ratio (WWR), and the material removal rate (MRR) have been performed using an L27 orthogonal array. The air/gas pressure, mixing water-flow rate, spark current, and pulse duration are considered as influencing parameters on the cutting characteristics. It was observed from a comparative analysis that the WWR of oxygen-mist and helium-mist CNDWEDM processes are 30.39 % and 27.91 % higher than air-mist CNDWEDM, respectively. The MRR of the oxygen-mist and helium-mist CNDWEDM processes are 7.09 % and 3.60 % higher than the air-mist CNDWEDM, respectively. The contributions of the process parameters on the MRR and WWR for all three dielectric media have also been illustrated. It was observed from scanning electron microscope (SEM) images that the crater size in the wire tool of the oxygen-mist CNDWEDM is higher than the crater-size of the wire in the air-mist and helium-mist CNDWEDM.</p> 2022-04-06T00:00:00+02:00 Copyright (c) 2022 Materials and Technology https://mater-tehnol.si/index.php/MatTech/article/view/329 STABILITY STUDIES OF COHESIVE SOIL WITH NANO MAGNESIUM AND ZINC OXIDE 2022-04-05T12:30:49+02:00 L. Veena Vijayan veenavijayanlphd@gmail.com J. Prakash Arul Jose vee3606@gmail.com <p>Cohesive soils are found all over the world and can cause significant harm to infrastructure and structures. Many innovative ways to improve the strength of cohesive soils are being explored to decrease the negative qualities and make them appropriate for construction applications. The availability of novel materials, in addition to traditional procedures, has boosted the area of soil reinforcement. In the realm of soil stabilisation, the inclusion of nanomaterials is one of the newest creative ideas. In geotechnical engineering, nanotechnology could be viewed as dual methods: the composition of the soil can be found at the nanoscale, and soil modification can be accomplished at the atomic and molecular levels. The goal of this research is to see if it is possible to stabilise cohesive soil using two distinct nanomaterials and to look at the changes in geotechnical parameters. Nanocrystalline magnesium oxide and nano zinc oxide is included in the soil with (0.25, 0.5, 0.75 and 1) <em>w</em>/% and trials were executed to evaluate the optimal percent and strength properties of the mixtures.</p> 2022-04-06T00:00:00+02:00 Copyright (c) 2022 Materials and Technology https://mater-tehnol.si/index.php/MatTech/article/view/336 SPINODAL DECOMPOSITION OF PRECIPITATION HARDENING Fe-17Cr-4Ni-4Cu STAINLESS STEEL AT 475 °C 2022-04-05T12:30:49+02:00 Xue Ma du511@163.com Zhijun Wang du511@163.com Xuezhu Tong du511@163.com Xaoming Du du511@163.com Tianfu Li du511@163.com Rongdeng Liu du511@163.com Yuntao Liu du511@163.com Dongfeng Chen du511@163.com <p>Microstructure evolution and mechanical properties in an Fe-17Cr-4Ni-4Cu alloy aged at 475 °C after different aging times were studied. Conventional transmission electron microscopy (TEM) and high-resolution electron microscopy (HREM) studies revealed the formation of 9R-structure Cu-rich precipitates and Cr-rich <em>α</em>’ phase by spinodal decomposition in the samples aged at 475 °C after 100–1000 h. The fine Cu-rich precipitates and Cr-rich <em>α</em>’ phase by spinodal decomposition lead to a significant increase in the hardness, together in the early stages (100 h). Continued aging to 500 h leads to increased precipitation of the Cr-rich <em>α</em>’, which provides significant strengthening, reaching maximum hardening, despite the continued loss of hardening by weakening by the Ostwald ripening of the Cu-rich precipitates. Extending the aging time to 1000 h leads to substantial reversed austenite transformation and a large number of ripening -copper precipitates that causes softening. The results of the impact tests showed that the major fracture mode was cleavage and/or quasi-cleavage.</p> 2022-04-06T00:00:00+02:00 Copyright (c) 2022 Materials and Technology https://mater-tehnol.si/index.php/MatTech/article/view/317 EFFECT OF COOLING RATE ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF SOLUTION-TREATED Mg-9Gd-4Y-2Zn-0.5Zr ALLOY 2022-04-05T12:30:50+02:00 Yong Xue YongXue395@163.com Zixuan Wang yongxue395@163.com Leichen Jia yongxue395@163.com Jie Zheng yongxue395@163.com Zhimin Zhang yongxue395@163.com Jianmin Yu yongxue395@163.com Xi Zhao yongxue395@163.com <p>Different cooling rates, such as room temperature water cooling (WQ), furnace cooling (FC), and water cooling + furnace cooling (FC +WQ), were introduced to study the effect on the solution-treated Mg-9Gd-4Y-2Zn-0.5Zr (<em>w</em>/%) alloy microstructure and mechanical properties. The grain size decreases as the cooling rate increases. With the lengthening of the cooling process time, the LPSO phase had enough time to nucleate and diffuse, the LPSO (long-period stacking order) phase filled the whole matrix crystal grains at the same time. In the process of furnace cooling and water cooling, the brightness of the LPSO phase was different, so it could be seen that the cooling rate would affect the contrast and morphology of the LPSO phase. The tensile yield strengths of the samples cooled with the furnace were better than those of the water-cooled samples, but their ultimate tensile strength and elongation to failure were poor. The fracture modes of the samples under different cooling rates were all subject to cleavage fracture, and the number and area of the cleavage planes and cleavage steps increased with the decrease of cooling speed, and the tearing area decreased, resulting in poor ultimate tensile strength and stretchability.</p> 2022-04-06T00:00:00+02:00 Copyright (c) 2022 Materials and Technology https://mater-tehnol.si/index.php/MatTech/article/view/384 MODIFIED DESIGN STRUCTURE OF A METAMATERIAL MICROSTRIP PATCH ARRAY ANTENNA FOR RF ENERGY OPTIMIZATION 2022-04-11T11:04:19+02:00 Beulah Jackson bjresearch001@gmail.com Saravanakumar R saravanakumarr.sse@saveetha.com Bhuvaneswari Balachander balachander@gmail.com Anandakumar Haldorai anandakumar.psgtech@gmail.com Varalakshmi S. drssvlakshmi@gmail.com Anselin Nisha A. Sahaya anselinnisha.ece@sathyabama.ac.in <p>We propose a modified design of a microstrip patch array antenna for RF energy optimization over 2.45 GHz WLAN communication applications. Initially, a one-patch and a two-patch array antennas were developed and considered as the base for the construction of a four-patch array antenna in the GSM 1800 frequency range. The energy usage by the WLAN application model includes a radiofrequency WLAN supply, a wireless connection, the proposed array antenna, impedance network matching, a voltage rectifier and a storage circuit that achieves higher efficiency. The proposed antenna design is utilized to examine the distance effect on the received RF power and it achieves the maximum efficiency of 47 % at 2.45 GHz at a 1-meter distance from the source. Improved gain is acquired at the expense of a greater array-antenna size with a -26 dB return loss, proving that it is much more efficient than other structures. Moreover, when experimentally analysed with HFSS, it delivers sufficient energy over WLAN applications.</p> 2022-04-06T00:00:00+02:00 Copyright (c) 2022 Materials and Technology https://mater-tehnol.si/index.php/MatTech/article/view/367 A MODIFIED TEST FOR DETERMINING THE FLUIDITY OF DUCTILE CAST IRON 2022-04-05T12:30:51+02:00 Matic Žbontar matic.zbontar@gmail.com Mitja Petrič matic.zbontar@ntf.uni-lj.si Primož Mrvar matic.zbontar@ntf.uni-lj.si <p>The aim of this experimental work was to design a modified test with which it will be possible to determine the fluidity of ductile cast iron. First, we planned the conceptual verification of the designed experiment, which was done by numerical simulations of the casting processes, followed by rapid mould fabrication using 3D printing. A measurement cell was placed in the mould cavity of the experimental chamber for further investigation of the cooling and solidification during casting. From the matrix of data obtained with the experiment, we defined the fluidity of the ductile iron EN-GJS-500-7. Also, we analysed the mechanical properties of the studied alloy, the microstructure, the chemical composition, and the results of the thermal analysis. In accordance with the expectations and theory from the literature, the fluidity in the experimental sample cast at a higher temperature was better than that cast at a lower temperature. Because of the faster cooling rate at the end of the channel of the experimental casting, the microstructure is fine, moreover, we obtain white solidification, ledeburite in the microstructure of the samples etched with Nital. At lower cooling rates, fewer graphite nodules appear in the microstructure, which are larger, and the portion of ferrite is greater.</p> 2022-04-06T00:00:00+02:00 Copyright (c) 2022 Materials and Technology https://mater-tehnol.si/index.php/MatTech/article/view/355 THERMAL-DEFORMATION MODEL OF A Sr-MODIFIED A356 ALUMINUM ALLOY 2022-04-05T12:30:51+02:00 Yongyue Liu rxp33@ustb.edu.cn Xianglai Xu rxp33@ustb.edu.cn Jiangxiong Cheng rxp33@ustb.edu.cn Hongwei Sun rxp33@ustb.edu.cn Xueping Ren rxp33@ustb.edu.cn Peng Jiang rxp33@ustb.edu.cn <p>The hot-deformation behavior of A356 aluminum alloy with a Sr modification was investigated using a Gleeble 1500 thermal simulator. The true stress-strain curves with a deformation temperature of 300–500 °C and a strain rate of 0.01–5 s<sup>–1</sup> were clarified. The activation energy of the A356 aluminum alloy with Sr modification was 221.474 kJ/mol. The influences of friction and temperature on the curves were investigated, and then the constitutive equation was established. The results show that the flow stress is obviously affected by temperature and strain rate. The experimental stress is lower than the theoretical stress, and the stress difference between the experimental and theoretical stress increases with the increasing strain. The maximum stress difference reaches 17.8 MPa when the sample deformed at 300 °C/5 s<sup>–1</sup> with a reduction of 16 %. For all the deformation conditions the correlation coefficient is 0.99 and the average relative error is 4.8 %, which shows the good predictability of the current model. The developed constitutive equation can provide guidance for the study of the hot-deformation behavior of similar aluminum alloys.</p> 2022-04-06T00:00:00+02:00 Copyright (c) 2022 Materials and Technology https://mater-tehnol.si/index.php/MatTech/article/view/406 INFLUENCE OF HEAT TREATMENT ON THE HIGH-TEMPERATURE OXIDATION BEHAVIOUR OF CHROMIUM-MOLYBDENUM-VANADIUM ALLOYED HOT-WORK TOOL STEEL 2022-04-05T12:30:52+02:00 Tilen Balaško tilen.balasko@ntf.uni-lj.si Maja Vončina tilen.balasko@ntf.uni-lj.si Jaka Burja tilen.balasko@ntf.uni-lj.si Jožef Medved tilen.balasko@ntf.uni-lj.si <p>The high-temperature oxidation behaviour of chromium-molybdenum-vanadium alloyed hot-work tool steel was investigated. High-temperature oxidation was investigated in two conditions: soft annealed, and quenched and tempered. The samples were oxidised in a chamber furnace and in an instrument for simultaneous thermal analysis, for 100 h in the temperature range between 400 °C and 700 °C. Metallographic analysis (optical and scanning electron microscopy) was performed to study the microstructural changes in the steel and the oxide layer. Oxidation kinetics were analysed by thermogravimetric analysis, and equations were derived from the results. The kinetics can be described by three mathematical functions, namely: exponential, parabolic and cubic. However, which function best describes the kinetics depends on the oxidation temperature and the thermal condition of the steel. Quenched and tempered samples were shown to oxidise less, resulting in a slower oxidation rate.</p> 2022-04-06T00:00:00+02:00 Copyright (c) 2022 Materials and Technology