In this study, aluminium alloys of AA6082 and AA7075 series were welded with resistance spot welding. Effects of welding current intensity, welding time, and electrode pressure on the tensile strength and microstructure were examined, and their optimized values were determined using the Taguchi method. While performing optimization, the L24 orthogonal array was used with the Taguchi method. With this array, the signal/noise (S/N) ratio became the determining factor in controlling the optimization results. Comparing the experimental procedures and analysis results, the results obtained from the real application and Taguchi analysis were found out to be similar.

In this study, the effect of niobium addition and a specific preheating process on the microstructure and tensile properties of 52CrMoV4 steel used in leaf springs was investigated. Flat and leaf spring materials were used to accomplish this aim. The flat materials under investigation were kept in a furnace for 90 min at 900 °C. A homogeneous microstructure was aimed for with the use of this pre-annealing heat treatment in addition to the standard process before rolling used to create NbC. Leaf spring production was carried out with flat materials that possessed various Nb contents, with or without pre-heating. Grain size measurement and tensile tests were performed on the flat and leaf springs. Additionally, scanning electron microscopy images were captured from the fractured surfaces after the tensile tests were carried out. The current study highlights the importance of Nb addition as an alloying element and the effect of the selected pre-annealing process in optimizing the grain structure and enhancing the tensile properties of leaf springs. The leaf spring with a Nb ratio of 0.0376 that was pre-annealed exhibited a finer grain structure (G = 11.3), greater tensile properties (YS = 1550 N/mm2 and UTS = 1688.6 N/mm2), and deeper tear valleys and larger dimples, indicating higher energy consumption during fracturing, according to the SEM images produced, in contrast with the other materials studied.

Sm0.2Ce0.8O1.9- 30% Na2CO3 (Sm doped ceria (SDC)-30N) nano-composite electrolytes were densified in a single step via cold sintering process (CSP). At 200 & DEG;C and 450 MPa of uniaxial pressure, samples up to 97% of their theoretical density could be obtained. The effect of processing parameters, such as temperature, uniaxial pressure, processing duration, and moisture content, on the densification of the nano-composite electrolytes was investigated. The thermal, microstructural, and electrical properties of nano-composites were investigated by differential scanning calorimetry, X-ray diffractometer, scanning electron microscope, and EIS analysis. SDC crystallite sizes were found to be around 25 nm, barely coarsened after CSP by which the true nano nature of the nano-composite could be preserved. Because, by conventional processing high density values could not be attained and high processing temperatures in excess of 600 & DEG;C had to be used, promoting particle coarsening. The highest total electrical conductivity was found to be 2.2 x 10(-2) S cm(-1) at 600 & DEG;C, with an activation energy of 0.83 eV for SDC-30N nano-composites. The present investigation revealed that the implementation of cold sintering technique resulted in significant enhancements in the densification of nano-composite electrolytes, thereby rendering them suitable for efficient utilization in SOFC applications, as compared to the conventional production methods.

Bu çalışmada, 8 mm kalınlığındaki HSS S960QL çelik plakalar %5 CO2 ve %20 CO2 içerikli iki farklı karışım gaz koruması altında 185, 215 ve 245 amper olmak üzere üç farklı kaynak akımında MAG kaynak yöntemiyle birleştirilmiştir. Uygulanan bu kaynak değişkenlerinin birleştirme denemelerinin kaynak bölgesi mekanik ve mikroyapı özelliklerine olan etkilerini tespit etmek amacıyla makro ve mikroyapı incelemelerinin yanı sıra çekme ve çentik darbe testleri ile mikrosertlik ölçümleri yapılmıştır. Gerçekleştirilen deneysel çalışma ve gözlem sonuçları göstermiştir ki kaynak akımı ve CO2 oranının artmasıyla, daha geniş ve derin nüfuziyete sahip bir kaynak metali meydana gelirken, kaynak bölgesinde başlangıç mikroyapısındaki temperlenmiş martenzitin beynite oranı azalmış, ayrıca buna tane irileşmesi de eşlik etmiştir. Dolayısıyla, sertlik ölçümlerinde artan akımla birlikte nispeten daha yavaş soğuma hızına bağlı olarak ısı tesiri altındaki bölgede ve kaynak metalinde sertlik düşüşleri belirlenmiştir. Ayrıca kaynak akımı ve CO2 miktarındaki artış, akma ve çekme dayanımlarının yanı sıra çentik darbe tokluğunu da düşürücü bir rol oynamıştır.

This study consisted of the effects of vertical tool load on failure value in FSSW of CuZn30. Tensile-shear test, microstructural examination, microhardness, vertical tool load, and temperature measurements were utilized to reveal the influence of FSSW process. According to the results, the tool load plays a key role on the features of joint. Not only low tool load, but also excessive load used leads to drop in the tensile-shear values. The spot weld region was characterized by stir and heat-affected zones and these have various microhardness values ranging from 108.2 HV to 150.2 HV. The temperature measurements show that the peak temperature increased with increasing tool load value..

This paper presents an experimental study on resistance spot welding of DP and TWIP steel sheets used in automative industry. A timer and current controlled resistance spot welding machine having 120 kVA capacity and a pneumatic application mechanism with a single lever was used to prepare the specimens. Welding periods were chosen as 5, 10, 15, 20, 25 and 30 cycles (1 cycle = 0.02 s) and also welding currents were increased from 6.33 kA up to 15.7 kA in steps of 0.9 kA. The electrode force was kept constant at 4 kN. The prepared welding specimens were exposed to tensile-peel test and micro and macro-structures of specimens were investigated by means of an optical microscope and scanning electron microscope (SEM) in order to see the joinability of DP and TWIP steel sheets by resistance spot welding. Finally appropriate welding current and time were advised to the users.

In this work, two different steels named 1200M (A martensitic steel has approximately 1200 MPa ultimate tensile strength) and DP 800 HF (A dualphase steel with 800 MPa yield strength and also in Hyper-Formed, easily formable) were joined by electrical resistance spot welding method. The tensile-peel test was preferred because it is a very similar test to the breaking action of the sheet metal at the time of the accident. The tensile-peel force was calculated to determine the strength of the joint which was affected by size of the weld zone (i.e. nugget diameter). For this reason, It is aimed to find the optimum parameters of the materials of two different structures, joined with different welding currents and welding periods and the results was supported by graphics. The electrical resistance spot welding parameters were selected as the weld current was started from 8440 Ampere and raised up to 15500 A; the weld time was selected as 5, 10, 15, 20, 25 and 30 periods.

In recent years, some topics in Automotive industry has become important such as energy saving, carbon emission and automotive safety issues. The main motivation to meet these requirements is employing high strength and low weight materials for vehicles. Therefore, the conventional materials have been substituted with Advanced High Strength Steels (AHSS) and High Strength Low Alloy (HSLA) steels that have high strength-to-weight ratios. However, in addition to material investigation, the joining and welding of these materials is of high importance cannot be underestimated. In this work, weldability of TRIP 800 (transformation induced plasticity), a AHSS steel, and microalloyed steels, a HSLA steel, with resistance spot welding has been investigated. The effect of welding time parameter on tensile-shear properties was analyzed. The optimum parameters for tensile-shear strengths and the encountered separation modes have been examined. The highest tensile-shear loads was obtained using 15 periods.

In this work, two different steels named 1200M (A martensitic steel has approximately 1200 MPa ultimate tensile strength) and DP 800 HF (A dualphase steel with 800 MPa yield strength and also in Hyper-Formed, easily formable) were joined by electrical resistance spot welding method. The tensile-shear test was preferred because it is a very similar test to the breaking action of the sheet metal at the time of the accident. The tensile-shear force was calculated to determine the strength of the joint which was affected by size of the weld zone (i.e. nugget diameter). For this reason, It is aimed to find the optimum parameters of the materials of two different structures, joined with different welding currents and welding periods and the results was supported by graphics.

This paper examines the effects of inoculant type and treatment material quantity on the mechanical and thermal properties of rail vehicle brake discs manufactured from vermicular graphite cast iron/compacted graphite iron (CGI). The in-mold treatment technique was employed in manufacturing the CGI brake discs. The main and interaction effects of inoculant type and treatment material quantity parameters affecting the tensile strength of the CGI brake discs were determined. The results indicate that treatment material quantity has the most significant effect on mechanical properties. Tensile strength was observed to increase as the treatment material quantity increased. The optimum level for manufacturing the CGI brake disc by using the in-mold treatment technique was attained via the combination of SB 5-type inoculant and 625 g treatment material quantity.

In this study, Aluminium 6082-T6 plates having 1.0 mm thickness were joined by magnesium-based (AlMg5) wire in cold metal transfer technique. The specimens were prepared in butt joint form. Argon was used as shielding gas and joining operations were done at gas flow speed of 13 l/min. The joining operations were carried out during four different working times of 25, 30, 35, 40 and 45 seconds. Tensile properties of joints were determined and macro-structures of joints were investigated in order to evaluate the joinability of Aluminium 6082-T6 alloy by cold metal transfer technique. Finally, the micro-hardness values of specimens were measured.

Bu calismada, 1,0 milimetre kalinliga sahip Aluminyum 6082-T6 plakalari magnezyum esasli (AlMg5) teliyle soguk metal transferi yontemiyle birlestirilmistir. Numuneler, alin birlestirme formunda hazirlanmistir. Koruyucu gaz olarak argon kullanilmistir ve birlestirme islemleri 20o calisma acisiyla yapilmistir. Soguk metal transferi yontemiyle farkli gaz basinclarinda kaynagi yapilan Aluminyum 6082 parcalarin cekme dayanimi degerleri belirlenmistir, sertlik degerleri olculmus ve makro yapilari optik mikroskopta incelenmistir.

Hydroxyapatite (HA) is an important material for biomedical implants, because its chemical composition is similar to that of bone tissue. This study focuses on the effect of sintering temperature and the amount of reinforcement phase on the mechanical properties of HA–Ti composites. Firstly, the production of hydroxyapatite powders that are consistent with the natural bone tissue was planned by means of chemical precipitation method. Secondly, the titanium element was added into this hydroxyapatite powder mixture by different amounts to investigate the change of mechanical properties. Titanium isopropoxide, Ti(OCH(CH3)2)4, was used as titanium supplier. These were solved and added into calcium solution without phosphate solution addition. In total, 0.5, 1, 2 and 4 mol% Ti were added into pure hydroxyapatite obtained by chemical precipitation method. The powders including different amounts of Ti additions were dried after the precipitation process and exposed to calcination at different temperatures in order to detect the phases obtained during the process. Microstructures have been investigated by SEM and EDS, and the phase analysis has been determined by the X-ray diffraction analysis, FTIR, DTA-TG and Raman spectrometers. The grain size and apparent density were measured. These results showed that titanium could enter into HA.

In this study, TRIP 800 (Transformation Induced Plasticity) steel plates, 1.5 mm in thickness, were joined with copper-based (CuAl8) wire by the gas metal arc brazing technique. Specimens were prepared in butt joint form. Five different working angles 50 degrees, 60 degrees, 70 degrees, 80 degrees and 90 degrees were selected for brazing operations. A copper based Cu Al8 wire was used as the filler metal. After the metal inert gas brazing process, butt joined specimens were exposed to tensile test in order to characterize the mechanical properties. The microstructure of the joints was investigated by scanning electron microscope (SEM) and optical microscope to see the joinability of TRIP 800 steel by gas metal arc brazing technique.

In this study, interstitial-free (IF) Erdemir 7116 and galvanized Erdemir 1315 steels having 1.0 mm thickness were joined by metal inert gas (MIG)-brazing method. CuAl8 wire was used as filler material. The specimens were cut in 200 mm × 200 mm dimensions and joined by using 40, 45, 50, 55, 60, 65 and 70 A currents both in butt and overlap joint forms. Having prepared the joints, all specimens were exposed to tensile test according to TS 138 EN 10002-1 standard. Micro and macro-structure investigation of samples were performed by optical microscope and scanning electron microscope (SEM). The matrix structure and the other phases occurred during brazing process were characterized and the effects of them on mechanical properties of joints were discussed.

Joints of DP 600 Thin Zinc Coated Steel Plates F. Varol, U. Ozsarac, S. Aslanlar, A. Onat, M. Ekici, E. Ferik Vocational School of Karasu, Sakarya University, Sakarya, Turkey Department of Metallurgical and Materials Engineering, Sakarya University, 54187 Sakarya, Turkey Marmara University, Technology Faculty, Department of Mechanical Engineering, Istanbul, Turkey Vocational School of Yalova, Yalova University, Yalova, Turkey

Purpose – The purpose of this study was to investigate wear behaviours of brake pads produced from carbon–carbon (C/C) composites in both wet and dry friction sliding conditions. Carbon is probably the most remarkable element in science and also C/C composites are a family of advanced composite materials. They are the most advanced form of carbon and consist of fibre based on carbon precursors embedded in a carbon matrix. In the present work, wear test specimens were prepared according to the related standards and they were exposed to pin-on-disc wear testing in wet and dry sliding conditions with different loads as 10, 20, 30 and 40 N with 1 m/s constant sliding speed. Wet friction process was conducted on all specimens by means of rain water collected from the nature. Design/methodology/approach – Pin-on-disc wear test tribology lubrication was used. Findings – Mechanical and physical property measurements of C/C composite brake pad materials: hardness, modulus of elasticity, density and water absorption capacity. Wear performance of materials were measured as coefficient of friction, volumetric loss and specific wear rate. Originality/value – C/C composite brake pads are used in railway vehicles. Wear performances of them are very important for safety. In this study, wear behaviours of these materials were investigated not only in dry sliding friction condition but also in wet sliding one. Because safety braking is important in all weather conditions for trains, and we used natural rain water to observe the wet sliding friction behaviour of brake pads. “Water lubrication” is an important aspect mentioned in tribology handbooks.

In this paper, austenitic 304L stainless steel plates having 1.0 mm thickness were joined by copper-based CuAl8 wire in gas metal arc brazing technique with 100 % Ar gas as a protective atmosphere. Specimens were prepared in butt and overlap joint positions. The metal inert gas (MIG) brazing operations were done with seven different arc voltages and weld currents as 40, 45, 50, 55, 60, 65 and 70 A. CuAl8 wire composed largely of copper serves as the filler metal was used. Owing to the low fusion temperature of the filler metal (900\(-\)1,100 \(^{\circ }\mathrm{C})\), no fusion of the base metal takes place in MIG-brazing. The 1,500 \(^{\circ }\mathrm{C}\) fusion temperature of the base metal was not reached. A solid joint between the workpieces was brought about by diffusion. Having accomplished the brazing operations, micro and macro-structures of joints were investigated by optical microscope and scanning electron microscope (SEM) in order to see the joinability of stainless steels by gas metal arc brazing technique.

In this study, the effect of martensite volume fraction on ductile to brittle transition of microalloyed steel joined by welding was investigated. Triple phase steel contains ferrite, perlite and martensite phases and was joined by two types of welding method as gas metal arc welding and the electric arc welding. Presence of three phases in adjacent to each other was confirmed by metallographic analysis and scanning electron microscopy studies. All welded samples were exposed to Charpy impact test at the temperature range of -30 degrees C to 30 degrees C in order to measure the fracture energies of samples having different amount of martensite volume fractions. The fracture surface micrographs of Charpy specimens, examined by scanning electron microscopy and optical microscopy, confirmed the reduction in ductility of ferrite perlite martensite steels with increasing martensite volume fraction.