Melting Point Of Aluminum Research Articles

Anti-sintering behavior and combustion process of aluminum nano particles coated with PTFE: A molecular dynamics study

The characteristic of easy sintering of aluminum nanoparticle (ANP) limits its application in solid propellants. Coating ANP with fluoropolymer could effectively improve its combustion performance. To find out how the coating layer inhibits sintering and promotes complete combustion of particles from an atomic view, a comparative study has been done for bare ANP and PTFE coated ANP by using reactive molecular dynamics simulations. The sintering process is quantified by shrinkage ratio and gyration radius. Our results show that, at the same heating rate and combustion temperatures, bare ANPs are sintered together after the temperature exceeds the melting point of aluminum but the decomposition of PTFE coating layer pushes particles away and increases reaction surface area by producing small Al–F clusters. The sintering of ANPs which are heated in PTFE is alleviated compared with particles heated in oxygen, but particles still sinter together due to the lack of intimate contact between PTFE and alumina surface. The effect of temperature on the combustion of PTFE coated ANPs is also studied from 1000 to 3500 K. The number density analysis shows the particles will not be sintered at any temperature. Aluminum fluoride prefers diffusing to the external space and the remained particles are mainly composed of Al, C and O. Fast ignition simulations are performed by adopting micro canonical ensemble. With the expansion of aluminum core and the melting of alumina shell, bare ANPs are sintered into a liquid particle directly. For PTFE coated ANPs, the volatilization of gaseous aluminum fluoride products continually endows particles opposite momentum.

The preferential formation of Ni2Al3, Fe2Al5, and Ti2Al5 phases in aluminide systems

The preferential formation of phases in Ni–Al, Fe–Al, and Ti–Al systems was observed at the interface of solid-solid and solid-liquid phases. It was found that phases already formed at temperatures lower than the melting point of aluminum. The Ni2Al3, Fe2Al5 and Ti2Al5 phases formed preferentially in the Ni–Al, Fe–Al and Ti–Al systems, respectively. The favored formation was not associated with thermodynamic assumptions, but was caused by crystal structures of arisen phases. The mentioned phases could form due to the two reasons, (i) similarities of their lattice parameters to lattice parameters of the individual elements (Ni, Fe, Ti, or Al) and (ii) the total volume of its lattice. The lattice volumes of Ni2Al3, Fe2Al5, and Ti2Al5 phases are always smaller than that of NiAl3, FeAl3, and TiAl3 phases. The last listed phases are ordinarily accepted by other authors as the phases, which form preferentially based on thermodynamic data only. This work disproves such claims and shows the reason for preferential phases' formation.

Hydrogen Solubility in Liquid and Solid Pure Aluminum—Critical Review of Measurement Methodologies and Reported Values

Reliable information on the solubility of hydrogen in aluminum and its alloys is critical to the effort of the aluminum industry to control and ameliorate the usually deleterious effects of hydrogen on the properties and performance of pure aluminum and aluminum alloy products. Unfortunately, there is a significant disparity between published values of hydrogen solubility in pure aluminum and aluminum alloys. This is because the measurement of the extremely low soluble hydrogen concentration in aluminum and its alloys is experimentally difficult. Also, the reproducibility, accuracy, and reliability of the hydrogen solubility values are very sensitive to the measurement techniques, test conditions, chemical composition, and state of the aluminum sample. Thus, no serious discussion of the reliability of reported values of hydrogen solubility in aluminum and its alloys can be undertaken without a critical assessment of the fundamental principles of the experimental techniques used in the determination of the reported values. In this article, a critical review of the fundamental principles of the experimental techniques used in the measurement of hydrogen solubility in liquid and solid pure aluminum and aluminum alloys is presented. In addition, the reliability and possible accuracy of reported values of hydrogen solubility in solid and liquid pure aluminum are critically assessed. Empirical equations for calculating hydrogen solubility in liquid and solid pure aluminum as a function of temperature and pressure, derived from the most reliable sets of data are recommended. At 101.3 kPa (1 atm.) hydrogen partial pressure, the most reliable values of hydrogen solubility at the melting point (833 K) of pure aluminum are 0.71 cm3/100g (i.e., 6.32 × 10-5 wt.% H) and 0.043 cm3/100g (i.e., 3.81 × 10-6 wt.% H), in the liquid and solid state, respectively. So, the partition coefficient of hydrogen in pure aluminum is 0.061.

Friction stir welding on temperature field for aluminum alloy based on combined HSM

A combined heat source model (HSM) is a new technology to resolve the welding problem of aluminum alloy in the friction stir welding (FSW) process. It authenticates advantage is solid-phase welding technology for magnesium, aluminum, and other low melting point alloy welding. Temperature field analysis is the prerequisite for improving the welding quality, welding metallurgy, and mechanical analysis. An accurate grasp of the temperature field distribution on the FSW process plays a vital role. In this research, the temperature field of FSW for 6005 aluminum alloy is simulated and analyzed by SYSWELD software. Then the simulation results were verified by experimental results. First of all, the finite element simulation and theoretical analysis were carried out for the FSW process. Then finite element model was established by using the SYSWELD software. And the temperature field of the FSW process was established by grid partitioning, HSM setting, and subsequent observation. The numerical simulation method is used to analyze the temperature field of the FSW process. Finally, the simulation results are verified and calibrated by the thermocouple temperature test. The influence of different welding parameters (Welding Speed and Rotational Speed) on the temperature field is evaluated by the thermal field curves analysis and some particular nodes analysis of the target area.

Intrinsic Diffusivities Ratio Analysis in Double Multiphase Systems

Our investigations show that electrochemical corrosion of copper is faster than electrochemical corrosion of aluminium at temperatures below 100°C. Literature data analysis shows that the Al atoms diffuse faster than the Cu atoms at temperatures higher than 475°C, Al rich intermetallic compounds (IMCs) are formed faster in the Cu-Al system, and the Kirkendall plane shifts toward the Al side. Electrochemical corrosion occurs due to electric current and due to diffusion. An electronic devise working time, for example, depends on initial copper cover thickness on aluminium wire, connected to the electronic devise, temperature, and volume and dislocation pipe diffusion coefficients, so copper, iron, and aluminium electrochemical corrosion rates are investigated experimentally at room temperature and at temperature 100°C. Intrinsic diffusivities ratios of copper and aluminium at different temperatures and diffusion activation energies in the Cu-Al system are calculated by proposed here methods using literature experimental data. Dislocation pipe and volume diffusion activation energies of pure iron are calculated separately by earlier proposed method using literature experimental data. Aluminium dissolved into NaCl solution as the Al3+ ions at room temperature and at temperature 100°C, iron dissolved into NaCl solution as the Fe2+ (not Fe3+) ions at room temperature and at temperature 100°C, copper dissolved into NaCl solution as the Cu+ ions at room temperature and as the Cu+ and the Cu2+ ions at temperature 100°C. It is found experimentally that copper corrosion is higher than aluminium corrosion, and ratio of electrochemical corrosion rates, kCu/kAl>1, decreases with temperature increasing, although iron electrochemical corrosion rate does not depend on temperature below 100°C. It is obvious, because the melting point of iron is more higher than the melting point of copper or aluminium. It is calculated that the copper electrochemical corrosion rate is approximately equal to aluminium electrochemical corrosion at temperature about 300°C, so copper can dissolve into NaCl solution mostly as the Cu2+ ions at temperature about 300°C. The ratio of intrinsic diffusivities, DCu/DAl<1, increases with temperature increasing, and the intrinsic diffusivity of aluminium could be approximately equal to the intrinsic diffusivity of copper at temperature about 460oC. Intrinsic diffusivities ratios in the Cu-Zn system at temperature 400°C and in the Cu-Sn system at temperatures from 190°C to 250°C are analyzed theoretically using literature experimental data. Diffusion activation energies and pre-exponential coefficients for the Cu-Sn system are calculated combining literature experimental results.

Removal of p-chloronitrobenzene from wastewater by aluminum and low melting point metals (Al-Ga-In-Sn) alloy

Recently, the methods of the degradation of p-chloronitrobenzene (p-CNB) have been studied by numerous scholars. In the present study, Al-Ga-In-Sn alloy was found to be able to effectively remove p-CNB. When the initial concentration of p-CNB was 10 µM, and the Al-Ga-In-Sn alloy dosage was 0.25 g, the p-CNB completely mineralized within 30 mins. The effects of the initial temperature, alloy dosage, pollutant concentration, pH and inorganic anions on the removal of organics were studied systematically. To characterize the alloy, XRD, SEM, XPS, HRTEM, EDX and DSC were respectively used, and the results thereof were used for proposing the mechanism of the reduction reaction. The reduction of p-CNB can be divided into four processes. The present study provides consideration of the utilization of Al-Ga-In-Sn alloy in the abatement of refractory pollutants in environments, in addition to an understanding of the mechanism of said system.

Mechanical and Microstructural Response of Aluminum Composites Reinforced with Ceramic Micro-Particles

Aluminum matrix composites have recently taken an important role in advanced applications because they have a good combination of physical and chemical properties. For this reason, in this work, aluminum composites, with additions of ceramic particles (mullite or tungsten carbide), were manufactured in order to determine the effect of those particles on the mechanical properties and microstructure of aluminum. The manufacture of the composites was carried out by means of powder metallurgy. We studied composites with additions of 0.5 and 1 vol.% of the respective ceramic. Composites were sintered at 580 and 601 °C, which corresponds to 88 and 91% of the melting point of aluminum, respectively. Observations in SEM, together with EDX analysis, confirm that mullite particles are located at intragranular and transgranular positions of the aluminum matrix, while tungsten carbide particles were found mostly at intragranular areas of the matrix. From the analysis of the studied ceramics, it was found that with the use of mullite, there are greater improvements in the hardness and elastic modulus of the manufactured composite.

A comprehensive description of reactions between nickel and aluminum powders during reactive sintering

In this work, Ni–14Al, Ni–30Al and Ni–58Al alloys representing Ni3Al, NiAl and NiAl3 phases were studied. First of all, they were prepared by reactive sintering to show which phases are present in the obtained microstructure. Subsequently, reactions between nickel and aluminum were observed below and above the melting point of aluminum allowing to propose reaction mechanism and to determine kinetics. Experiments below melting point were carried out as annealing of the powder mixture and phase composition was studied while experiments at higher temperatures used special experimental model consisting bulk nickel and molten aluminum. Results showed that Ni2Al3 phase formed preferentially in all alloy composition, which was supported by in-situ diffraction analysis, and the whole process was controlled by diffusion. Its preferential formation was confirmed by annealing of powder mixture and by the experimental model as well. This model allowed observing the phases' formation at the interface of bulk nickel and molten aluminum at high temperature. The appropriate ongoing reactions were compiled for each alloy with calculated Gibbs energy and enthalpy of reaction.

Establishing the interface layer on the aluminum surface through the self-assembly of tannic acid (TA): Improving the ignition and combustion properties of aluminum

Aluminum powder is widely used in the field of propellants and explosives due to its high energy density. However, the dense oxide film on its surface will hinder the combustion of aluminum powder. Herein, Al@TA-Fe with core-shell structure was prepared by self-assembly of tannic acid (TA) and Fe(III) ion on the surface of aluminum, and was characterized by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and thermogravimetry-differential scanning calorimetry (TG-DSC). The results show that the TA-Fe interface layer in Al@TA-Fe can effectively promote the ignition of aluminum powder, which can make the aluminum powder be ignited at the temperature far below the melting point of aluminum. Meanwhile, the carbides formed by the decomposition of tannic acid are beneficial to the cracking of the alumina on the surface of the aluminum powder, which can promote the internal aluminum to participate in the reaction and improve the reaction efficiency of aluminum. The TA-Fe layer can inhibit the agglomeration of molten aluminum during the combustion of aluminum and can effectively improve the corrosion resistance of aluminum powder. The iron ions in the TA-Fe interface layer can successfullycatalyze the thermal decomposition process of ammonium perchlorate (AP). In addition, Al@TA-Fe can effectively increase the burning rate of the propellant compared with pure aluminum powder.

Effect of Copper Addition on the AlCoCrFeNi High Entropy Alloys Properties via the Electroless Plating and Powder Metallurgy Technique

To improve the AlCoCrFeNi high entropy alloys’ (HEAs’) toughness, it was coated with different amounts of Cu then fabricated by the powder metallurgy technique. Mechanical alloying of equiatomic AlCoCrFeNi HEAs for 25 h preceded the coating process. The established powder samples were sintered at different temperatures in a vacuum furnace. The HEAs samples sintered at 950 °C exhibit the highest relative density. The AlCoCrFeNi HEAs model sample was not successfully produced by the applied method due to the low melting point of aluminum. The Al element’s problem disappeared due to encapsulating it with a copper layer during the coating process. Because the atomic radius of the copper metal (0.1278 nm) is less than the atomic radius of the aluminum metal (0.1431 nm) and nearly equal to the rest of the other elements (Co, Cr, Fe, and Ni), the crystal size powder and fabricated samples decreased by increasing the content of the Cu wt%. On the other hand, the lattice strain increased. The microstructure revealed that the complete diffusion between the different elements to form high entropy alloy material was not achieved. A dramatic decrease in the produced samples’ hardness was observed where it decreased from 403 HV at 5 wt% Cu to 191 HV at 20 wt% Cu. On the contrary, the compressive strength increased from 400.034 MPa at 5 wt% Cu to 599.527 MPa at 15 wt% Cu with a 49.86% increment. This increment in the compressive strength may be due to precipitating the copper metal on the particles’ surface in the nano-size, reducing the dislocations’ motion, increasing the stiffness of produced materials. The formability and toughness of the fabricated materials improved by increasing the copper’s content. The thermal expansion has increased gradually by increasing the Cu wt%.

FORMATION OF THE STRUCTURE AND COMPOSITION OF THE DIFFUSION INTERACTION ZONE DURING THE HEAT TREATMENT OF THE EXPLOSION-WELDED AD1 + Cr20Ni80 COMPOSITE IN THE PRESENCE OF A LIQUID PHASE

The paper presents the study results of the structure, chemical and phase composition of the diffusion coating formed during the heat treatment of the explosion-welded Cr20Ni80 + AD1 bimetal according to the regime providing liquid-phase interaction (above the melting point of aluminum) on the surface of the Cr20Ni80 alloy. It is shown that its structure consists of inclusions of NiAl, CrAl, NiAl intermetallic compounds, as well as a metastable ternary compound - τ-phase with composition of AlCrNi of different dispersion and morphology. There are no crystallization defects in the coating structure.

Performance and wear mechanisms of uncoated, TiAlN, and AlTiN-coated carbide tools in high-speed drilling of Al-Si alloy

Owning to the extremely abrasive silicon particles, low melting point of aluminum, and its susceptibility to adhere to the tool, high-speed drilling of aluminum alloys containing high silicon content becomes a challenging operation. Hence, the understanding of the tool wear mechanisms is essential in order to develop and select the efficient tool material. This paper reports on the investigation of performance and wear mechanism of uncoated and TiAlN and AlTiN-coated tools when high-speed drilling of Al-Si (A383) alloy. Drilling tests were conducted at various cutting parameters, while thrust forces were measured using a dynamometer. The wear mechanisms that contributed to the drill failure were assessed by analyzing the worn cutting edge and drill bit cross section; and by employing scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). Results showed that feed rate has the highest effect on the primary wear stage; and flank wear at the outer cutting edge found to be dominant failure mode for all tools. Moreover, it is found that plastic deformation, diffusion, attrition, abrasion, and fracture are the main operating tool wear mechanisms. The longest tool life was recorded for AlTiN-coated tool, but more adhesion of Al was observed on this tool surface. At the end, TiAlN-coated drill was proposed as the tool with the best performance among the tool materials used in this study.

Systematic growth of carbon nanotubes on aluminum substrate for enhanced field emission performance

For more than two decades, carbon nanotubes (CNTs) have shown great potential for a wide range of applications. Several methods are known to synthesize CNTs, though only a few of them are able to produce good quality and economically available CNTs. Chemical vapor deposition (CVD) is one of those methods that produce economically feasible and good quality CNTs onto specific substrates, even with nanopatterning. However, growing CNTs by CVD at temperatures below 700 °C remained a long-time challenge, as this meant keeping a host of low-melting materials out of bounds for direct CNT growth on them. In this work, CNTs have been synthesized directly onto a low-melting, conducting substrate, aluminum, by thermal CVD, at a temperature as low as 550 °C and up to as high as 650 °C (just below the melting point of aluminum). The diameters of the grown CNTs were observed to be influenced by process parameters, e.g., temperature and pressure. The effect of synthesis parameters on CNT diameters was verified by scanning electron microscopy and transmission electron microscopy. The quality of the CNTs was checked by Raman spectroscopy, selected area electron diffraction pattern of transmission electron microscopy, and XPS. It was observed that an increase in temperature and pressure had a significant effect on the diameters of the CNTs. Randomly entangled CNTs were measured to have an average diameter of 28 nm at 550 °C and one atmospheric (760 Torr) pressure, whereas it was observed to be 78 nm at a temperature of 650 °C and pressure of 0.01 Torr. The field emission response, i.e., the turn-on field (2.5 V/μm) and the maximum emission current density (2.17 mA/cm2) of the CNTs synthesized at the temperature of 550 °C and pressure of 1 atm (760 Torr) was found to be excellent.

Enhancements of mechanical properties of materials through ECAP for high temperature applications

In the recent past aerospace industries are facing great challenges in enhancing the efficiency of jet engines in order to reduce the fuel consumption. This has led to a rigorous research in the field of advanced materials especially alloys and composites for jet engines. As evident, the melting point of aluminium is much lower than engine’s operating temperature which gives an edge over for the use of alloys and composites. In hotter parts of a turbine engine, temperature rises as high as to 1800 °C. Materials like intermetallic alloys, refractory materials e.g. ceramics and composites are now being used at a wide scale. In the current study mechanical properties after grain refinement of super alloys and composites being used in aircraft engine is carried out using Equal Channel Angular Pressing (ECAP). In the current study effect of ECAP on Al-SiC composite has been mainly studied. And Al-SiC composite has been majorly used by the aircraft manufacturers in the recent Boeing aircraft 787. It is expected that the present investigation will be useful for developing super alloys and composites for high temperature applications.

Investigation into defects occurred in friction stir welded joint of 6061-T6 aluminium alloy

Due to the low melting point of aluminium (Al) alloys, it is difficult to join them by fusion welding techniques. After immense research in the field of welding, especially solid state welding processes, it was ascertained that friction stir welding (FSW) processes might be able to eliminate these difficulties. Although the FSW provides a strong bonding, some defects are often reported in the welded joint. These defects are generally responsible for making the joint weak. A continuous research is going on to assess the wear phenomena in FS welded joint. In the present work, a case study was done for analyzing various defects occurred in FS-welded Al 6061-T6 alloy. For the purpose, an augmented vertical milling machine was used as a FSW machine. Total six plates of Al-alloy were taken to make three joints. Welding was done through a non-consumable tool made of AISI D2 steel. The tool rotation and travel speed were selected as two different process parameters during welding. After joining the metals, five different major defects, such as, deformed base, flash, blow holes, bulged edges and collapsed pin were observed. A detailed explanation, including both quantitative and qualitative, behind each defects are discussed comprehensively in this work.

Formation Mechanism of High-Purity Ti2AlN Powders under Microwave Sintering.

In the present study, high-purity ternary-phase nitride (Ti2AlN) powders were synthesized through microwave sintering using TiH2, Al, and TiN powders as raw materials. X-ray diffraction (XRD), differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) were adopted to characterize the as-prepared powders. It was found that the Ti2AlN powder prepared by the microwave sintering of the 1TiH2/1.15Al/1TiN mixture at 1250 °C for 30 min manifested great purity (96.68%) with uniform grain size distribution. The formation mechanism of Ti2AlN occurred in four stages. The solid-phase reaction of Ti/Al and Ti/TiN took place below the melting point of aluminum and formed Ti2Al and TiN0.5 phases, which were the main intermediates in Ti2AlN formation. Therefore, the present work puts forward a favorable method for the preparation of high-purity Ti2AlN powders.

Numerical and experimental investigation on aluminum 6061-V-grooved stainless steel 304 explosive cladding

This study attempts to analyze the microstructure and interface behavior of aluminum 6061 (Al 6061)-V-grooved stainless steel (SS304) explosive cladding by numerical and experimental methods. Numerical simulation was performed by Smoothed Particle Hydrodynamics (SPH) technique, in ANSYS AUTODYN, and the results are correlated with experimental outcome. The machining of V-grooves on the base plate transform the melted layer formed in conventional cladding (without grooves on the base plate) into a smooth undulating interface, for a similar experimental condition. The flyer plate and collision velocities, observed in numerical simulation, are in good agreement to the analytical expectations. The pressure developed in the flyer plate is higher than the base plate and the maximum pressure is witnessed at the collision point irrespective of grooved base plate or otherwise. The temperature developed in the collision point of conventional explosive cladding exceeds the melting point of both the participant metals, whereas, it exceeds the melting point of aluminum alone, in case of V-grooved base plate cladding. The shear and impact strengths of the V-grooved base plate clads are higher than the conventional clads and the fracture surfaces exhibit mixed modes of fracture.

Mechanism of formation of intermetallic coatings by the Cold Spray Technology

In the present paper, results of a study of a TinAlm intermetallic coating obtained on the surface of titanium (Ti) by the method of Cold Gas Spraying (CGS) and heating to a temperature above the melting point of aluminum (Al) are reported. It is shown that the structure of the resultant coating depends on the heating temperature. At temperature T = 930K the coating consists of a TiAl3 intermetallic layer. At temperature T = 1270K a layered coating is formed. In this coating, a TiAl3 intermetallic layer, adjacent to the Ti surface, is followed by a second intermetallic layer consisting of Ti3Al and Ti2Al sublayers. The microhardness of the Ti3Al/Ti2Al double-layer coating proves to be three times higher than that of Ti. A qualitative explanation to the mechanism of formation of the layered coating is proposed.

Experimental investigation on effect of titanium reinforcement in aluminium metal matrix composites

In this research work, a novel composite has been fabricated by stir casting method and then its properties have been founded. This composite consists of pure Aluminum (melting point of 660.4 °C) as base or matrix metal and Titanium (melting point of 1660 °C) as a fiber or reinforcement material, in which titanium has been added to aluminium in the ratio of 3% and 6% by weight as per ASTM (American standards for testing materials) standards.The fabricated specimens are subjected to mechanical tests by using universal testing machine (UTM) in order to evaluate the mechanical properties of the newly obtained Al-Ti metal matrix composite. The obtained properties are compared to pure aluminium (100% Al and 0% Ti) and also with medium carbon steel (generally used for manufacturing of connecting rod).It is observed from the results that, the mechanical properties like tensile strength, compressive strength and yield strength are high in case of Al + 6%Ti composite material.

Formation of Phases in Reactively Sintered TiAl3 Alloy.

This work highlights new results on the synthesis of the TiAl3 intermetallic phase using self-propagating high-temperature synthesis. This method is considered a promising sintering route for intermetallic compounds. It was found that the reactions proceed in two stages. Below the melting point of aluminum, the Ti2Al5 phase forms at 450 °C after long annealing times by a direct solid-state reaction between the aluminum and titanium, and is converted consequently to TiAl3. This is a completely new finding; until now, many authors have believed in the preferential formation of the TiAl3 phase. The second stage, the self-propagating strongly exothermic reaction, proceeds above the melting point of aluminum. It leads to the formation of the TiAl3 phase accompanied by Ti2Al5 and Ti3Al phases. The reaction mechanism was shown in the form of chemical equations, which were supported by calculating Gibbs energy. Reaction temperatures (Tonset, Tmaximum, and Toffset) were determined after induction heating thanks to recording by an optical pyrometer. This finding provides completely new opportunities for the determination of activation energy at heating rates, in which common calorimeters are not able to detect a response or even measure. Now, the whole procedure will become accessible.