The aim of the present research work was to investigate tribological performance and potential of Ni-based self-lubricating claddings for high temperature forming of lightweight alloys. Laser claddings included in this investigation were based on Ni-matrix with the incorporation of 5 wt% silver and 10 wt% MoS2 as solid lubricant precursors. Tribological evaluation and testing was performed by Load- Scanner to simulate hot forming process and results compared to high performance hot work tool steel. To simulate hot forming process of forging, wire drawing and extrusion, tests were done at room and elevated temperatures (150°C and 300°C) against typical light-weight alloys, including AISI 316L stainless steel, 6xxx series Al alloy and Ti6Al4V Ti alloy and results evaluated in terms of coefficient of friction vs. load, critical loads for galling initiation and volume of adhered work material. Results show that self-lubricated claddings with incorporated MoS2 and Ag as solid lubricants in general provide lower and more stable friction as well as improved galling resistance in high temperature forming of lightweight alloys. Positive effect of self-lubricating claddings intensifies with forming temperature, degree of plastic deformation and work material tendency to galling.

The effect of quench rate on the width of precipitate free zone was examined in aluminum alloys 7075 and 7050. It was determined that at quench rates greater than 60°C/sec., vacancy depletion dominated. At slower quench rates, it was determined that solute depletion dominated the precipitate free zone. The critical vacancy concentration for precipitation was established as a function of quench rate.

Aluminum alloy 6061 (AA6061) is widely used in industry due to its excellent formability, corrosion resistance, weldability, and strong mechanical properties after heat treatment. AA6061 is hardened through precipitation of alloying elements that act as blockers to dislocation paths in the individual aluminum grains, increasing mechanical performance. During artificial aging, these nano-scale precipitates combine and form the main hardening phase, β’’. The general heat treatment procedure for AA6061 follows a solution treatment, quench, and a direct artificial aging. The focus of this work is to develop the parameters for a materials model for AA6061 which can predict the material response to heat treatment by modeling the kinetics of precipitation formation and coarsening. This work uses data from publications found in the public domain to develop the solution kinetics, artificial aging and coarsening kinetics, and resulting mechanical properties. Another publication was used to validate the developed DANTE model by comparing hardness predictions to hardness obtained in an actual component.

The work presented in this paper addresses a data gap that continues to be a hinderance to users of precipitation modeling tools, particularly those based on Langer-Schwartz theory. Thermodynamic and kinetic data required for precipitation models can be obtained from CALPHAD databases, but interfacial energies between the bulk and precipitate phases are not available for many alloy systems. In this work, a number of matrix-precipitate interfacial energies have been determined for influential precipitates in alloys of industrial importance, for example, carbides in Grade 22 low-alloy steels, delta phase in Ni 625 and 718, S-phase in Al 2024, and Q’ and β’’ in Al 6111.

Undesired distortion can arise during machining of metals from two main mechanisms: 1) release of bulk residual stress in the pre-form, and 2) deformation induced by the cutting tool. The interaction between these two mechanisms is explored herein using aluminum plate-shaped samples that have a large surface with variations of bulk residual stress (BRS), where that surface is subsequently milled and we observe milling-induced residual stress (MIRS) and distortion. Plate samples are cut from two kinds of large blocks, one kind stress-relieved by stretching and a second kind that had been solution heat treated, quenched, and aged. MIRS is measured following milling using hole-drilling with fine depth increments. Distortions of thin wafers cut at the milled surfaces are used to show how the interactions between BRS and MIRS change milling-induced distortion. Data from the study show that the directions of MIRS and distortion relative to the milling direction are changed when milling in samples with high BRS magnitude (roughly ±100 MPa), with the direction of maximum curvature rotating toward or away from the milling direction depending on the sign and direction of BRS. High magnitude BRS increased distortion, nearly doubling the amount found compared to milling in samples free of BRS.

Although many have had success using CFD and FEA techniques to predict residual stress and distortion in water quenched aluminum alloys, there are still hurdles in using a computational approach to manage liquid quenching processes due to the lack of a quench severity database. Quench severity is defined by the Grossman number, which does not serve as a heat transfer model for CFD simulation because it omits much of the underlying physics. In this research, a new interpretation of quench severity makes it possible to separate the heat transfer model into two groups, one computable by CFD and one requiring calibration. The objective of this paper is to parameterize the boiling model by quenching conditions and validate the model using data obtained by quenchometer testing.

In industrial applications, hot forging of aluminum alloy AA 6082 is carried out at 480 °C following a preheating process in an induction heater. The forged parts are then cooled down to room temperature, heated up again to apply conventional solution treatment followed by quenching and artificial aging processes. Repetitive heating/cooling steps are a significant cause of energy loss. The aim of this study was to provide time and energy efficiency by combining hot forging and solution treatment processes in a single high temperature process. To achieve this a new and improved heat treatment pattern was introduced. AA6082 parts were quenched immediately from a rather high forging temperature and artificially aged without any necessity for a second heating step and solution treatment. Mechanical properties of parts heat treated by this new pattern were than compared to the mechanical properties of parts heat treated conventionally. Heat treatment of AA6082 alloys were carried out for 30 minutes at three different temperatures (480, 510 and 540 °C) for comparison, followed by forging, water quenching and artificial aging (180°C, 8h). Mechanical properties of each sample were investigated using hardness and tensile tests. Elemental analysis and microstructural characterization were carried out using Energy Dispersive Spectrometry (EDS), Scanning Electron Microscope (SEM) and Optical Microscope (OM). Required minimum hardness for the samples after heat treatment was considered as 90 HB. This hardness value could not be obtained for the parts forged/solution treated at 480°C and 510°C. Hardness values of parts heat treated at 540°C, water quenched and aged at 180°C were higher than 90 HB.

High entropy alloys (HEA) are an exciting new class of alloys composed of several metallic elements with equiatomic or near-equiatomic composition to maximize configurational entropy, leading to desirable properties. However, during solidification, as in casting or welding processes, elements segregate, creating local regions of distinct composition. In conventional alloy systems, homogenization heat treatments are used to remove this segregation effect. This study examines the conditions of the heat treatment needed in HEA alloys. First, the solidification behavior of equiatomic alloy composition AlCoCrCuFeNi is modeled using the Scheil module within Thermo-Calc along with the TCHEA2 database. Energy dispersive spectroscopy (EDS) is performed across the dendrite arms of the as-melted HEA to compare with the Scheil calculations. The resulting dendritic and interdendritic compositions are used as inputs in Thermo- Calc to determine the stable phases as a function of temperature. Selected heat treatments are conducted on the as-melted HEA to compare with the calculation results.

This paper describes the uphill quenching process which is applied in the heat treatment of aluminum alloys. This lesser known process was developed by Alcoa and first applied more than 50 years ago for aluminum alloys of several thicknesses. Uphill quenching has been reported to reduce residual stresses by > 80%. Typically, uphill quenching is applied after quenching and before aging of aluminum alloys. Uphill quenching consists of the immersion of the part in a cryogenic environment and after equilibration, the part is transferred immediately to a fixture in a superheated steam chamber to obtain a temperature gradient sufficient to maintain the improved mechanical properties gained with heat treatment that result in low residual stresses and superior dimensional stability. Assuming that most of the stresses that appear in aluminum alloys during heat treatment are due to the quenching process, then this intermediate treatment becomes a potentially effective tool for the heat treatment of aluminum alloys. The aim of this paper is to present an overview of recent work showing tensile test results obtained with uphill quenching relative to conventional quenching processes.

The use of aluminum alloys in automotive and other industries is due to their excellent combination of weight and strength, which is obtained by heat treating. The alloying elements are put in solution by holding the material at a high temperature, and cooling at a rate fast enough to allow them to remain in solution; strengthening is then produced by the precipitation of particles of different size, shape and nature. This work presents the results of the analyses of samples made from cast aluminum alloys hardened by either the precipitation of Mg 2 Si or Al 2 Cu and of an alloy that has both. The samples were solution treated at temperatures adequate for the different alloys and cooled by placing them in water close to boiling. Aging was conducted at two different temperatures (170 and 240°C) in all cases for times as long as 100 hrs. Changes due to aging were documented by microhardeness, microscopical examination and by X-ray diffraction. X-ray examination showed that the peak corresponding to the {311} position shifts the aging condition, indicating changes in the lattice parameter of aluminum, which depends on the type of particle that precipitates.

As automobile manufactures today push the envelope of light weighting technologies, so do they impart opportunities for the development of new thermal processing technologies. In an era of light weighting technology advancement, we see a common trend where steel components are being replaced with lighter weight aluminum components. We see automotive manufactures expanding the use of lightweight technologies and exploiting the use of aluminum materials in high volume general purpose vehicles where in the past these lightweight technologies were relegated to high performance or luxury vehicles. Traditionally we see aluminum being incorporated in various forms and configurations such as castings for powertrains and suspensions and sheet and extruded shapes for the body externals and bumper structures. Today we see lightweight materials being incorporated into high volume automotive platforms in the form of thin walled structural node castings and body structure extrusion stampings.

Aluminum alloys are used intensively by the automotive industry to comply with environmental and fuel consumption regulations. These alloys were first used in the manufacture of power train components, and they have extended their use in parts and assemblies of structural components. Power train and structural components have to be heat treated to achieve the strength and hardness demanded, which imply solution treating, quenching and aging. Quenching is the most critical part of processing, as the material has to be cooled at rates high enough to allow for the hardening elements to remain in solution, but the rate has to be controlled to avoid distortion or, in some cases, catastrophic failure. Distortion is associated with the geometry of the piece, as heavy components have sections of different volume, which will cool at different rates, or, in the case of long thin pieces, warpage may arise from variations in cooling rate along the length of the part. This work presents the results of a series of tests carried out with the aim to evaluate the variation of the heat transfer coefficients that take occur in pieces made of a heat treatable wrought aluminum alloy cooled in different media. The heat transfer coefficients were used to compute the temperature distribution of a modified version of the Navy C specimen.

The solution quenching process is a critical heat treatment process for aluminum alloys to obtain better strength and a homogeneous super solid solution. In this paper, the mechanical properties of Al-5%Cu-0.4%Mn in the as-quenched state are tested. The alloy, designated as ZL205 (Chinese standard), has a chemical composition similar to a 2xxx series aluminum alloy and is used for constructing large thin wall components. The ZL205A alloy shows good performance under loading at room temperature while losing its toughness and exhibiting tensile brittleness, which is unexpected at elevated temperatures (especially at 300 °C). After observing the fracture sections of ZL205A at room temperature and at 300 °C, it may be concluded that one possible reason leading to this phenomenon may be the formation of the T phase at grain boundaries. Such a hypothesis is validated and discussed with the help of SEM observations.

The properties of heat treatable wrought aluminum alloys are primarily achieved through use of solution heat treatment processes defined in AMS 2770. Variation in these processes can greatly influence the final properties of the aluminum alloy material. This study specifically investigates the effects of the quenching solution used during the wrought aluminum alloy heat treatment process. The research varies the Type 1 polymer concentrations between 10 and 25 percent in the quenchant solution. The scope is limited to investigate aluminum 6061 and 7075 alloys treated to the T6 condition and uses plate stock ranging 1 to 2.5 inches in thickness. Statistical analysis is used to determine the magnitude of the effect of polymer percentage on material properties of the aluminum alloys at these conditions. This research is conducted to determine the basis for the glycol restrictions within the ranges typical to internal manufacturing processes. The conclusions of this research are based on statistical evaluation of tensile, yield, hardness, grain size and electrical conductivity results obtained as a result of the investigation.

Metallurgical properties required in aluminum alloys are highly dependent on the cooling uniformity during the quenching process. Non-uniformity during cooling is associated with piece distortion and failure. Although the quenching process is considered the most critical step during alloy heat treating, quench tank design is still based mainly on experience. Computational fluid dynamics (CFD) offers detailed understanding of the complex behavior of fluid flow and its impact on part cooling. Detailed cooling rates can then be used to predict part metallurgical properties. Although computational fluid dynamics are being used increasingly in quench tank design, there is still considerable imprecision due to assumptions that must be made. In this work, cooling curves are obtained for a 25 mm diameter 6061 aluminum cylinder probe under different conditions. Results are also obtained numerically via computational fluid dynamics. Results show the suitability for designing quench systems based on CFD simulations.

The 2524 aluminum alloy was cold rolled to 70% reduction and then annealed at 500? for 0.5h in an air furnace with a heating rate of 5?/min and in a salt bath with a heating rate of 75?/s, respectively. The effect of heating rate on the microstructure, tensile properties and fatigue crack growth (FCG) rate of the alloy was investigated. The microstructure and mechanical properties of the alloy were studied by means of transmission electron microscopy (TEM), scanning electron microscopy (SEM), optical microscopy (OM), tensile and FCG rate tests. In the case of slow heating the alloy exhibited a coarse elongated grain structure (~75μm), while a fine equiaxed grain structure (~13μm) was obtained in the case of rapid heating. The sheet annealed with rapid heating has slightly higher tensile strength and yield strength, but a slightly lower elongation than the sheet annealed with slow heating. The FCG rate of the sheet annealed with slow heating is 20% lower than the sheet annealed with rapid heating.

AHTF (Aerodynamic Heat Treating Furnaces) furnaces, in which air or gas is heated to 600-700°C without electrical or other special heaters, have been developed and placed in operation in a number of plants for heat treating aluminum, magnesium, and titanium alloys, and also steels. The AHTF chamber furnace is thermally insulated without the use of firebricks. It has a centrifugal fan with vanes having a special contour. The fan, operating in a closed system, converts, into heat, almost all the energy used to turn it; the heat is transferred to the parts by convection. In most machine-building plants aluminum alloys are heat treated in ERF furnaces (electric resistance furnaces with forced air circulation) or in salt baths. This research deals with an investigation of the heating conditions for various semi-finished products of aluminum alloys in the AHTF-3 in comparison with the ERF-2 (Electrical Recirculation Furnace) furnace and a potassium nitrate bath of approximately the same working volume.

The high-strength aluminum alloy V92Zr, part of the Al-Zn-Mg system, is a self-quenched alloy. Its primary alloying elements include 4.2 wt% Mg, 3.2 wt% Zn, 0.6 wt% Mn, and 0.15 wt% Zr. The most suitable filler wires for welding this alloy are V92W, AMg6, AMg4Zr, and No.11 (Al-Zn-Mg). This alloy is applicable in aircraft production. Prolonged heating at 50-70°C can lead to significant structural changes in the precipitation hardening of aluminum alloys due to the transition from zone aging to phase aging. Studies indicate that zone aging of Al-Zn-Mg alloys, particularly in weld seams, with repeated heating at 50-70°C, substantially increases strength while reducing elongation, cross-sectional area reduction, toughness, stress corrosion resistance, and increasing susceptibility to cracking. Research has shown that even heating at temperatures below the phase aging threshold can significantly alter the properties. This article examines the effects of prolonged low-temperature heating on the mechanical properties, crack sensitivity in impact bending, and corrosion resistance of semi-finished products and weldments of V92Zr aluminum alloys after solution treatment and aging at room and elevated temperatures.