Sustainable production of intermetallic nanocomposites from aluminum and iron scarp, with excellent tribo-mechanical and thermal properties for industrial applications

Functional graded nanocomposites (FGNCs) based on Al are artificially tailored heterogeneous materials intended to serve the demand for diverse and contradicting properties used in various industrial applications. FGNCs and hybrid FGNCs (HFGNCs) based on Al reinforced with graphene and vanadium carbide (VC) were prepared using powder metallurgy techniques and investigated. Both samples were designed with a gradient composition, where the bottom layer consisted of 100% pure Al, followed by three consecutive layers containing progressively increasing amounts of reinforcement. The incorporation of graphene and VC into layer powders resulted in a decrease in both particle and crystal dimensions compared to pure Al. Adding graphene has a negative effect on bulk density samples, while VC has a positive effect. Reinforcing materials led to a decrease in thermal conductivity that reached 26.7% for samples reinforced with VC reinforcement, except for FGNCs reinforced with graphene, which increased by ∼3.3 compared to Al. The samples’ CTE and electrical conductivity values decreased, although adding graphene alone led to a slight decrease in electrical conductivity. A significant improvement in all mechanical properties was noted with additional. The HFGCNs reinforced with the largest amount of hybrid reinforcement recorded an improvement in CTE value, Young’s modulus, and compressive strength by about 38.1%, 22.2%, and 20.5%, respectively, compared to Al.

IMC growth of Sn-3.5Ag/Cu system: Combined chemical reaction and diffusion mechanisms

Strengthening high entropy alloys (HEAs) via second phases is a very effective approach. However, the design of intermetallic (IM) phases in HEAs is challenging, mainly because our understanding of IM phases in HEAs is still very limited. Here, a statistical approach is used to enhance our understanding towards IM phases in HEAs. A database consisting of 142 IM-containing HEAs was constructed. Our aim is twofold. The first is to reveal the most common IM phase types in published HEAs. The second is to understand whether HEAs inherit their IM structures from their binary/ternary subsystems, or whether they tend to form new structures irrelevant to their subsystems. The results show that the five most prevalent IM structures in the HEAs surveyed here are Laves, σ, B2, L12, and L21. This trend is evidently different from the overall trend among known binary/ternary IMs. As for structural inheritance, all the IM phases contained in the alloys are existing structures in the binary/ternary subsystems of the respective alloys. This suggests that the compositional complexity in HEAs does trigger additional complexity in IM structure formation. These findings have important implications in the future design and development of HEAs.

Ordered intermetallic platinum phases have been recently proposed as promising materials in the oxidation of organic compounds in fuel cells. These intermetallic phases present constant crystallographic structure for the whole body of the material and they configure in a class of materials with very well defined physical-chemical characteristics and with an accentuated stability with consequent reproducibility of their properties. The study of the intermetallic phases has fundamental importance for the wide and efficient spread of the fuel cells because the anode commonly used, Platinum, is easy and irreversibility blocked by intermediates and/or products of the reactions. The proper characterization of the electrode material assumes crucial importance in the electrocatalysis, allowing the investigation of the geometric structure, as well as the distribution of the electronic density at the surface as determining parameters of the electrocatalysis. X-Ray Diffraction (XRD) technique is a powerful tool for the characterization of crystalline materials, based on the dispersion of an x-ray beam by the atom planes that constitute the crystalline lattice of the sample. The results of the characterization of the intermetallic phases PtSn 2 , PtSn, Pt 3 Sn, PtMn 3 , PtMn and Pt 3 Mn by the XRD technique attested their crystalline characteristics and confirmed that the variation of the distances among the sites of adsorption was achieveds.

Exposure of lead free solder joints to high temperature isothermal aging conditions leads to microstructure evolution, which mainly includes coarsening of the intermetallic (IMC) phases. In our previous work, it was found that the coarsening of IMCs led to degradation of the overall mechanical properties of the SAC solder composite consisting of β-Sn matrix and IMC particles. However, it is not known whether the isothermal aging changes properties of the individual β-Sn and IMC phases, which could also be affecting to the overall degradation of properties. In this study, the aging induced variations of the mechanical properties of the β-Sn phase, and of Sn-Cu IMC particles in SAC solder joints have been explored using nanoindentation. SAC solder joints extracted from SuperBGA (SBGA) packages were aged for different time intervals (0, 1, 5, 10 days) at T = 125 °C. Nanoindentation test samples were prepared by cross sectioning the solder joints, and then molding them in epoxy and polishing them to prepare the joint surfaces for nanoindentation. Multiple β-Sn grains were identified in joints using optical polarized microscopy and IMCs were also observed. Individual β-Sn grains and IMC particles were then indented at room temperature to measure their mechanical properties (elastic modulus and hardness) and time dependent creep deformations. Properties measured at different aging time were then compared to explore aging induced degradations of the individual phases. The properties of the individual phases did not show significant degradation. Thus, IMC coarsening is the primary reason for the degradation of bulk solder joint properties, and changes of the properties of the individual phases making up the lead free solder material are negligible.

Chapter 4 - Structure of Intermetallic Compounds and Phases

Thomas F. Fässler

Soldering has become an indispensable joining process in the electronic packaging industry. The industry is aiming for the use of environment friendly lead-free solders. All the lead-free solders are high tin-containing alloys. During the soldering process, an intense interaction of metallization on PCB and tin from the solder occurs at the metallization/solder interface. Intermetallic compound (IMC) is formed at the interface and subsequently PCB bond-metal (substrate) is dissolved into the molten solder. In the present study the terms bond-metal and substrate will be used interchangeably and the term 'substrate' refers to the top layer of the PCB which comes in contact with the molten solder during soldering reaction. Thickness of the intermetallic phase formed at the joint interface and amount of substrate lost is critical in achieving reliable solder joints. During the wet phase of soldering process, the IMC does not grow as layered structure; rather it takes the shape of scallops. The growth of scalloped IMC during the solder/substrate interaction entails complicated physics. Understanding of the actual kinetics involved in the formation of IMC phase is important in controlling the process to achieve desired results. This paper presents theoretical analysis of the kinetics involved in the formation of the scalloped intermetallic phase. The intermetallic phase growth is experimentally investigated to support the underlying kinetics of the process. Numerical model has been suggested to translate the physics of the process. The model is based on the basic mass diffusion equations and can predict the substrate dissolution and IMC thickness as a function of soldering time.

The paper presents preliminary results of research on the production of composite coatings from the Fe-Al system with participation of intermetallic phases in-situ using arc spraying. The spraying process was carried out by simultaneously melting two different electrode wires, aluminium and steel. The aim of the research is to create protective coatings with a composite structure with a significant participation of Fe x Al y as a intermetallic phases reinforcement. The synthesis of intermetallic takes place during the (in-situ) spraying process. Currently most of coatings involving intermetallic phases are being manufactured by different thermal spraying methods using coating materials in form of prefabricated powders containing intermetallic phases. The obtained results showed that the local occurrence of intermetallic phases from the Fe-Al system, and the dominant components of the structure are two phases, aluminium solid solutions in iron and iron in aluminium. The participation of intermetallic phases in the coating is relatively low, but it’s effect on the properties of the coating material is significant.

Kinetics of interface alloy phase formation at nanometer length scale in ultra-thin films: X-ray and polarized neutron reflectometry

The increasingly extreme and aggressive service conditions caused by today’s technological advancements have necessitated a continuous improvement in the surface dependent properties of engineering materials. This study was designed to investigate the enhancement in the surface hardness of AA1200 laser alloyed with premixed ratio of Mo+Zr+Stellite 6 using a 4.4 kW continuous wave (CW) Rofin Sinar Nd:YAG laser processing system. Microstructural evolution in the alloyed samples was studied by optical and scanning electron microscopes while phase identification was studied by x-ray diffractometer. A through-thickness hardness of the coating was measured using Vickers hardness tester. The results show the existence of metallurgical bonding between the AA1200 substrate and the fabricated MMC. SEM/EDS and XRD spectra of the MMC revealed the precipitation and modification of new and fine intermetallic compounds and alloy phases. Molybdenum in the powder mix promoted grain size refinement in the coated samples. There was considerable increase in the Vickers hardness from an average of 30.57 HV0.1 in the native alloy to an average of 280.95 HV0.1 in the MMC. This could be attributed to the evolution of metallic and intermetallic phases such as Co2.74 O4 (identified as spinel by XRD), Zirconium Aluminide (ZrAl3) Aluminium Cobalt Iron (AlCo2Fe) and Cobalt Molybdenum (Co0.08 Mo0.92) in the MMC.The increasingly extreme and aggressive service conditions caused by today’s technological advancements have necessitated a continuous improvement in the surface dependent properties of engineering materials. This study was designed to investigate the enhancement in the surface hardness of AA1200 laser alloyed with premixed ratio of Mo+Zr+Stellite 6 using a 4.4 kW continuous wave (CW) Rofin Sinar Nd:YAG laser processing system. Microstructural evolution in the alloyed samples was studied by optical and scanning electron microscopes while phase identification was studied by x-ray diffractometer. A through-thickness hardness of the coating was measured using Vickers hardness tester. The results show the existence of metallurgical bonding between the AA1200 substrate and the fabricated MMC. SEM/EDS and XRD spectra of the MMC revealed the precipitation and modification of new and fine intermetallic compounds and alloy phases. Molybdenum in the powder mix promoted grain size refinement in the coated samples. T...

Intermetallic compounds from the Fe-Al system are attracting increasing attention due to their outstanding properties, including excellent mechanical performance, low density, corrosion, and oxidation resistance, as well as resistance to sulfidation, carburization, and wear at elevated temperatures. These unique characteristics make Fe-Al intermetallics promising candidates for high-temperature and harsh environmental applications. However, challenges such as brittleness and low plasticity have hindered their broader use. By exploring the impact of spray conditions on coating properties, this study contributes to enhancing the performance and functionality of Fe-Al coatings in industrial applications, where durability and resistance to extreme conditions are essential. This article presents the results of research on the production of composite coatings from the Fe-Al system with in situ fabricated intermetallic phases. For this purpose, arc spraying in an inert gas was used. The coating manufacturing process was carried out by simultaneously melting two different electrode filler wires, aluminum and steel, in a stream of argon. The obtained coatings were subjected to tests of roughness, adhesion to the substrate, and microstructure. It was shown that both the roughness and adhesion to the substrate of coatings sprayed in air are higher than those sprayed in argon. The increase in roughness results from the greater oxidation of coatings sprayed in air, while better adhesion is the result of the formation of coatings at a higher temperature. Metallographic studies have shown that during the spraying process, the in situ synthesis of intermetallic phases occurred. The results showed the local occurrence of intermetallic phases from the Fe-Al system. Among the two dominant phases, i.e., Al and the Fe alloy, there are also the following phases: FeAl3, FeAl2, and Fe2Al5. Furthermore, in layers sprayed in an inert atmosphere, the share of oxides is small.

The high-intensity, high-resolution x-ray source at the European Synchrotron Radiation Facility (ESRF) has been used in x-ray diffraction (XRD) experiments to detect intermetallic compounds (IMCs) in lead-free solder bumps. The IMCs found in 95.5Sn3.8Ag0.7Cu solder bumps on Cu pads with electroplated-nickel immersion-gold (ENIG) surface finish are consistent with results based on traditional destructive methods. Moreover, after positive identification of the IMCs from the diffraction data, spatial distribution plots over the entire bump were obtained. These spatial distributions for selected intermetallic phases display the layer thickness and confirm the locations of the IMCs. For isothermally aged solder samples, results have shown that much thicker layers of IMCs have grown from the pad interface into the bulk of the solder. Additionally, the XRD technique has also been used in a temperature-resolved mode to observe the formation of IMCs, in situ, during the solidification of the solder joint. The results demonstrate that the XRD technique is very attractive as it allows for nondestructive investigations to be performed on expensive state-of-the-art electronic components, thereby allowing new, lead-free materials to be fully characterized.

The interfacial reaction and growth of intermetallic compounds (IMCs) between the eutectic Sn-0.7 wt.% Cu solder and Cu substrate during soldering process were investigated experimentally. The Sn-0.7Cu/Cu couples were fabricated with soldering temperature varied at four levels of 300, 340 and 360°C. Microstructural analysis is conducted to analyze the IMCs thickness and morphology using scanning electron microscope. Two intermetallic phases were observed during soldering at the interface: η-phase (Cu6Sn5) and ε-phase (Cu3Sn) IMC layers, except for the solder joints which were fabricated at low temperature. The thickness of the η and ε IMC phases increase with increasing the soldering temperature. It’s found that the increase in total IMC layer thickness obeys a linear relationship with soldering temperature. And the relationship between X and T was given as X = 0.0866×T – 22.5 by means of linear fitting method.

The interfacial reaction and growth of intermetallic compounds (IMCs) between the eutectic Sn-0.7 wt.% Cu solder and Cu substrate during soldering process were investigated experimentally. The Sn-0.7Cu/Cu couples were fabricated with soldering temperature varied at four levels of 300, 320, 340 and 360°C, while soldering time is varied at five levels between 5 and 90 min. Microstructural analysis is conducted to analyze the IMCs thickness and morphology. Two intermetallic phases were observed during soldering at the interface: η-phase (Cu 6 Sn 5 ) and e-phase (Cu 3 Sn) IMC layers, except for the solder joints which were fabricated at low temperature and/or short soldering time. The thickness of the η and e IMC phases increase with increasing the soldering temperature and/or soldering time. It's found that the increase in total IMC layer thickness obeys a linear relationship with soldering temperature. And the relationship between X and T was given as X = 0.0866×T − 22.5 by means of linear fitting method.