Aluminum-copper System Research Articles

Prediction of the shear strength of aluminum with θ phase inclusions based on precipitate statistics, dislocation and molecular dynamics

We propose a three-stage technique for predicting the flow stress of aluminum alloy combining atomistic calculations, parameterizing the dislocation–precipitate interaction model, and 2D dislocation dynamics. The precipitates of θ phase in aluminum matrix are considered as the object of atomistic calculations in this work. It is shown that, in contrast to the previously studied precipitates of the aluminum-copper system (GP zones, θ'' and θ' phases), θ phase appears as uncuttable inclusion during our atomistic study demonstrating only significant bending of its shape. The obtained rate and temperature dependencies of the average stress in the system are used to find the parameters of the previously proposed model of the dislocation–precipitate interaction (Krasnikov and Mayer, 2019; Krasnikov et al., 2020) in the case of θ phase. After fitting of the model parameters, the equation of motion of the dislocation in the presence of inclusions of θ phase is used in 2D dislocation dynamics. The dislocation dynamics model employs the experimental data on the size distribution of precipitates (Zuiko and Kaibyshev, 2018). The obtained values of the flow stresses of alloy demonstrate good agreement with the experimental results, and the dislocation dynamics model predicts the correct value of the thermal softening of alloy. The model predicts a strict dependence of the flow stress of alloy on the dispersion of the size distribution of precipitates at the constant average size.

Study of the Influence of Heat Treatment on the Structure and Properties of Aluminum-Copper Multilayer Systems

Multilayer intermetallic composite materials of the aluminum-copper system are obtained using a complex technology, including explosion welding, rolling and diffusion heat treatment. The structure, composition and properties of the obtained 9 and 15-layer systems were studied and it was shown that the applied technology makes it possible to obtain qualitative multilayer systems with a large proportion of intermetallide phases, that have properties that are significantly different from the base metals, which makes it possible to expand significantly the areas of application of aluminum composites-copper.

Diffusion in thin bilayer films during rapid thermal annealing

The knowledge of pre-exponential factors and activation energies for low temperatures and short annealing times in nanoscaled systems is important for the downscaling of thermal processes. Here, the diffusion coefficients in aluminum–nickel, aluminum–titanium, titanium–silicon, and aluminum–copper bilayers were determined using rapid thermal annealing. The annealing time was set to 500 s and the investigated bilayer thin film thicknesses were 2 µm. The temperatures ranged from 389 to 613 K depending on the bilayer system. For the various material combinations, the diffusion coefficients were determined by elemental depth profiling and compared to literature values. For the aluminum–copper system, a good agreement with literature and a single set of values was found, whereas for aluminum–nickel, aluminum–titanium, and titanium–silicon two or more sets of values were observed.

High-pressure torsion for enhanced atomic diffusion and promoting solid-state reactions in the aluminum–copper system

This study reports that solid-state reactions occur by the application of high-pressure torsion (HPT) to the Al–Cu system even at low homologous temperature. A bulk form of disc consisting of two separate half-discs of pure Al and pure Cu are processed by HPT at ambient temperature under a pressure of 6GPa. X-ray diffraction analysis and high-resolution transmission electron microscopy confirm the formation of different intermetallic phases such as Al2Cu, AlCu and Al4Cu9, as well as the dissolution and supersaturation of Al and Cu in each matrix. It is shown that the diffusion coefficient is enhanced by 1012–1022 times during the HPT processing in comparison with the lattice diffusion and becomes comparable to the surface diffusion. The enhanced diffusion is attributed to the presence of a high density of lattice defects such as vacancies, dislocations and grain boundaries produced by HPT processing.

Patterning Alloy Precipitates through Tailored Surface Loading

An innovative processing technique that produces distinct, locally patterned microstructures within a single sample is introduced in this article. This technique alters the conventional heat-treatment process by applying a micropatterned external surface load to selected locations during the quench and anneal. In the aluminum-copper system (2 wt pct Cu), spatial control of Al2Cu precipitates within 50 μm features over an aggregate length scale of millimeters is achieved. Chemical interactions among the furnace environment, the alloy sample, and the loading device can affect the experiments adversely and steps used to ameliorate these effects are discussed. The precipitate patterning technique presented in this article is compatible with standard “heat and beat” processing and could be used potentially to develop new multifunctional metallic alloys.

Intermetallic Formation in the Aluminum–Copper System

Intermetallic formation at 425°C in the aluminum–copper system has been studied by scanning electron microscopy using welded diffusion couples. Several Al–Cu phases predicted by the equilibrium phase diagram of the elements and voids taking place in the diffusion zone have been detected in the couples. The predominant phases were found to be Al 2 Cu 3 and the solid solution of Al in Cu, α. The growth of the intermetallic layer obeyed the parabolic law.

Microstructural and compositional transients during accelerated directional solidification of Al-4.5 wt pct Cu

The transient behavior of mushy-zone velocities, primary dendrite arm spacings, and microsegregation effects have been investigated for an Al-4.5 wt pct Cu alloy by instantaneous velocity changes in a standard Bridgman furnace. After suddenly imposed velocity changes, the mushy-zone velocities, dendrite arm spacings, and compositions exponentially adjust to new steady-state values. Good agreement was found between the transient mushy-zone positions and velocities and predictions from the theoretical model of Saitou and Hirata. The primary dendrite arm spacings appear to adjust to changed velocity conditions about as rapidly as the mushy-zone velocity adjusts. Steady-state arm spacings agree very well with corresponding steady-state data from the literature. However, the observed composition profiles in the dendrite core and the interdendritic liquid appear to adjust more slowly than the corresponding adjustment of the mushy-zone velocity and arm spacings. Our observation of the sluggish response of the compositional profiles is consistent with an estimated Lewis number \((Le = \frac{k}{{c_p \rho D}})\) of 9.4 × 103 for the aluminum-copper system. The diffusivity of heat, thus, greatly exceeds the diffusivity of solute in this system. These results indicate that testing for the steady state during directional solidification experiments by looking for constant primary dendrite arm spacings can lead to errors, since the microsegregation profiles adjust more slowly than the spacings. It is suggested that constancy of composition also be tested for critical experiments investigating steady-state microsegregation effects.

Nature of the growth of Al-Cu powder compacts during liquid-phase sintering

Arresting the process of liquid-phase sintering of aluminum-copper system powder compacts by rapid cooling does not affect the character of the volume changes experienced by them during subsequent sintering under the same temperature conditions. In the growth stage a decrease in the crystal lattice parameter of aluminum and an appreciable broadening of an x-ray line have been observed, caused by the formation of aluminum base solid solutions. These findings bear out the hypothesis that the growth of aluminum-copper powder compacts above their eutectic melting point is mainly due to diffusion of copper from the liquid phase into aluminum particles.

The aluminium-copper system

The aluminium-copper system

The aluminium-copper system

AbstractA critical assessment is given of the phase equilibria of the AI-Cu system. In the first section, the stable equilibrium diagram is constructed. In the second section, metastable and constrained equilibria are considered. These include metastable solvus curves of the AI-rich side of the diagram; on the Cu-rich side, transformations involving the metastable bcc phase include the order-disorder transition, metastable invariant reactions, and martensitic and massive transformation. In the third section, crystal structure and lattice-parameter data are reviewed. Finally, new calculations of selected phase equilibria are presented which are based on computer optimization of phase-diagram and thermochemical data.

The aluminium-copper system

The aluminium-copper system

Lattice Images at θ’ Precipitates in Al-3%Cu Alloy

As part of a high resolution electron microscopic study of the precipitation sequence at 130°C in aluminum - 3% copper alloy, we studied G. P. [1], G. P. [2] or θ”, and θ’ precipitates by the lattice imaging technique. This approach proved valuable for phase identification and distinction. Examples of cros sed-lattice and c-plane lattice images at θ’ platelets will be presented here.Slices were spark cut nearly parallel to {001} from a melt-grown single crystal of aluminum -3.0 wt. % copper, previously solution treated at540°C and water quenched. Slices were aged at 130°C in argon and hand ground. Discs were chemically, electrolytically or in one case ion thinned, and examined at 100 kV in a slightly modified Philips EM 300 microscope.In the aluminum-copper system, the intermediate phases (G. P. zones and θ’) separate parallel to cube matrix planes, so that the slice orientation chosen resulted in two sets of platelets being parallel and one set normal to the beam.

Crystal Structure of the Intermetallic Compound Mg32(AI,Zn)49 and Related Phases

PHASE-DIAGRAM studies of the magnesium–aluminium–zinc system have established the existence of a compound with approximate composition Mg3Al2Zn3. Laves, Lohberg and Witte1 reported this compound to have a body-centred cubic structure with a0 = 14.16 A., and with the calculated number of atoms per unit cube equal to 161. They reported also that the phase in the magnesium–aluminium–copper system with approximate composition Mg4Al6Cu gives a closely similar X-ray diagram. They were not able to determine the structure.