Papers by Keyword: Intermetallic

Abstract: Steel 22MnB5 is widely used in the automotive industry for manufacturing high-strength structural car body parts. To achieve desired mechanical properties, hot-stamping is used, during which the Al-Si coating plays a critical protective role against oxidation. This study investigates the structural evolution of the Al-Si coating under various austenitization durations at 920 °C. Intermetallic phase formation and coating morphology are analyzed.

Abstract: The microstructure and growth kinetic of alumina (Al₂O₃)-modified aluminide coating were investigated at 650°C, 680°C, and 700°C for various durations (4, 6, 8, and 10 hours) using the slurry aluminizing process. The heat-treated samples were analyzed through scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) to assess microstructural evolution, elemental composition, and phases of the coating. SEM observations revealed a two-layer aluminide coating, comprising an Al-rich intermetallic (FeAl₃) and a Fe-rich intermetallic (FeAl). Microhardness tests showed that FeAl₃ had hardness values ranging from 880 to 990 HV, while FeAl, with values between 610 and 700 HV. The growth kinetics indicated that the thickness of the aluminide layers increased with both the aluminizing temperature and time, following a parabolic growth law. The activation energy for the growth of FeAl was 343.15 kJ/mol.

Abstract: Aluminium and titanium are currently in demand as lightweight materials. However, their combination is challenging due to their significantly different thermo-mechanical properties. Here, solid-state joining processes such as Friction Stir Welding open up new opportunities. Within this study, four commercial aluminium alloys (AA2024, AA5754, AA6056 and AA7050) were welded to Ti6Al4V. The results show a direct relationship between the solidus temperature of the aluminium alloys, the process temperature, energy input and resulting lap-shear strength. Regardless of the process parameters, AA5754 and AA6056 with higher solidus temperatures (600 °C and 555 °C) show superior bonding strength compared to AA2024 and AA7050, having a lower solidus temperature of 500 °C and 490 °C, respectively. Therefore, it is assumed that the maximum process temperature, proportional to the solidus temperature, has a major influence on the bonding. This, conversely, would imply that there is a physical limitation in the achievable joint strength between aluminium and titanium alloys as the required process temperature would exceed the solidus temperature of certain alloys. This assumption is verified for AA7050 by systematic variation of the rotation speed and therefore process temperature.

Abstract: The sintering at (1.35x103) °C for 90 minutes under argon gas atmosphere formed a nickel aluminide NiAl-based composite strengthened with yttrium oxide Y₂O₃ with the addition of cobalt in the current sample. (ASTM E140 – 12b) was used to perform the Brinell hardness test. The addition of cobalt increases the hardness of the (NiAl-Y₂O₃) composite. The hardness of NiAl-30Y₂O₃ composite improved from 341HB to 359HB after 1.5 wt.% Co was added, although the hardness improved to (381-383)HB after 2-2.5 percent Co was added. According to the findings of the wear examination, the inclusion of cobalt decreases the wear intensity of NiAl-30Y₂O₃, according to the findings of the wear examination. The adhesion wear rate reduces from 7.61 * 10^-6 gr / cm to 6.72 * 10^-6 gr / cm when 1.5 wt. percent Co is added, thus inserting 2-2.5 wt. percent Co reduces the rate to 5.87* 10^-6 – 5.22* 10^-6 gr /cm.

Abstract: Coatings were obtained by the method of electrospark deposition (ESD), using Ni-Al intermetallic alloys, steel having been used as cathodes. The structure of samples preliminarily, coated with nickel aluminides of various phase compositions (NiAl, Ni₃Al), was investigated. In addition to the indicated anode materials, a complex alloyed metal matrix alloy obtained by the method of self-propagating high-temperature synthesis, was used. It was established that the coating microstructure consisted of columnar crystallites, vertically oriented to the cathode surface. X-ray microanalysis of the transverse sections showed a change in the composition of crystallites along their height. It was found that the content of the cathode components decreased from the surface of the sample to the upper part of its coating, however, the content of the anode components increased. The revealed regularities indicate the fact that the coating structure obtained at ESD, was formed through the stage of liquid-phase mixing, which explained high coating adheasion. The mechanisms of structure formation of both single-layer and two-layer coatings proved to be identical.

Abstract: The work is devoted to studying of possibility to manufacture cast ball valves of sucker rod oil pumps instead of those manufactured by the powder metallurgy method from Stellite 20 alloy. It is shown that Stellite 20 cast alloy includes about 20% μ and σ brittle phases, destruction whereof, in case of impact-abrasion wear, when excavating oil, leads to quick failure of the valve pair. A new cast cobalt alloy not containing brittle phases has been developed instead of Stellite 20 alloy, which allowed to improve wear resistance of cast valve pairs to the level of valves produced by the powder metallurgy method.

Abstract: The objectives of the study is to investigate the formation of intermetallic compound and the mechanical properties of the underwater welding. AISI 4012 steel was selected as the material and two types of electrode E6013 and E7018. The variations of electric current used in this study were 80,100, and 120 amperes. The underwater welding was conducted in plain water pool and 3 meters depth by using SMAW. Tensile test and SEM-EDS were carried out to investigate the tensile strength and appearence the intermetallic layer.The results of this study indicated that the highest value of tensile stresswas found on the use E7018 electrodes and 80 amperes electric current. While the lowest value was found in the use E6013 electrodes with 120 amperes. Intermetallic layer was detected base on the SEM-EDS investigation.

Abstract: High entropy alloys (HEAs) generally exhibit either high resistance to deformation or high toughness due to the presence of body-centered or face-centered cubic structure, respectively. To overcome these limitations, new high entropy alloys have been developed in the present study. This investigation aims to synthesis and characterization of novel CoCrFeNi₃Si, CoCrFe₂Ni₂Si, and Co₂CrFeNi₂Si high entropy alloys. The mechanical alloying route is used to synthesize these alloys. Grinding was carried out to 20h and X-ray diffraction (XRD) analysis was done at different time intervals of grinding. The face-centered cubic structure along with the intermetallic compound of Ni-Si was observed after 20h of grinding. Furthermore, a pseudo binary strategy based on the valence electron concentration and mixing enthalpy is also employed to design the high entropy alloys considered in the present study. Carefully analysis of the XRD pattern indicates that from 5 to 20h of mechanical alloying there is a decrement in the initial peaks of elements observed.

Abstract: A dissimilar metal joining method based on diffusion bonding was developed to join 304L stainless steel (SS) and Zr alloy (Zy-4). This was done at 820°C and 950°C under argon and dynamic pressure for 45 minutes.The metallurgical structure of the interface and the evolution of its texture during the treatment were studied by evaluating the distribution of the constituent chemical elements and by identifying the crystalline phases formed. Chemical exchanges through the interface are favored by diffusion phenomena. The junction was characterized by: microscopic observations and chemical analyzes (ESEM-EDS, EPMA), X-RD and mechanical tests (HV and Shear test). Treatment at 820°C does not form a bond because the reciprocal solubilities of the chemical elements of SS and Zy-4 are very low. The junction obtained at 950°C has a reaction zone (RZ) formed at the SS/Zy-4 interface, composed of three layers. The first layer (LI = α-(Fe,Cr) on the SS side and the third layer (LIII=Zr₂(Fe, Ni)) on the Zy-4 side are single-phased. The middle layer LII is biphasic (LII= e-Zr(Cr,Fe)₂+Zr₂(Fe, Ni)). The maximum hardness measured in the RZ is ~ 1120 HV. It is due to the formation of the intermetallic compounds of type e-Zr(Cr,Fe)₂ in LII. Examination of fracture facies obtained from the joints reveals that the fracture is localized in the LIII layer and it is fragile in nature of the trans-granular type.

Abstract: High entropy alloys (HEA’s) have found a very special place in aerospace industries due to their property of forming solid solution. In past literatures on high entropy alloys, it is established that parameters like atomic size difference (), topological parameter (Ω) and electro-negativity difference (∆) plays a vital role in deciding whether solid solution will be formed or not. Therefore, the present study deals with the selection of optimal high entropy composition based on the three parameters δ, Ω and with the help of TOPSIS (Technique for Order of Preference by Similarity to Ideal Solution). Ranking is done for 38 HEA different compositions such that the first rank represents the HEA which is most likely to form solid solution. The study reveals that TOPSIS method can be successfully implemented to predict the formation of solid solution in HEA’s.