Microstructure Evolution and Grain Growth Competition in Directionally Solidified Ternary Al–Ag2Al–Al2Cu Eutectic

Metallurgical and Materials Transactions A - Eutectics serve as an interesting material class for fundamental research on solidification as well as holding promise for new, high-tech applications....     

Lead Dispersion During Smelting Aluminum Alloys of the Al–Cu–Mg System with Addition of Pb Under Structure Formation Regulation Conditions

Metallurgist - Dispersion of lead during smelting wrought aluminum alloys of the Al–Cu–Mg system with Pb additives and coarsening of lead-bearing phase particles during casting have a...     

Production of Al–Cu and Al–Cu–Si Alloys by PM Methods

Abstract

The possibilities of the production of aluminium-base copper and/or silicon alloys by conventional powder compaction and sintering methods have been studied. The effects of various lubricants, pressing, and sintering conditions on the behaviour of Al–Cu and Al–Cu–Si alloys were evaluated systematically. The role of copper and silicon additions during compaction and sintering and their advantages or disadvantages are discussed. All alloys underwent large dimensional changes (sudden swelling followed by rapid contraction) during sintering at temperatures greater than Al–Cu eutectic temperature and it is suggested that a process of particle rearrangement is largely responsible for this behaviour. The mechanical properties of the alloys were highly dependent on the sintering temperature. PM/0215     

Constitution of the Al Corner in the Ternary Al–Ge–Mg Phase Diagram

Powder Metallurgy and Metal Ceramics - A fragment of the Al corner in the ternary Al–Ge–Mg phase diagram has been constructed. Experimental methods have shown that the tie-line of the L...     

Investigation of the Thermal and Electrical Properties of Al–1.9Mn–xFe Ternary Alloys

Russian Journal of Non-Ferrous Metals - In this work, the thermal conductivity, electrical conductivity, enthalpy of fusion, specific heat capacity and thermal diffusivity of the...     

Experiments on the aging of Sn–Ag–Cu solder alloys

Abstract

The microstructural stability of the Sn–3·8%Ag–0·7%Cu solder alloy was investigated by studying microstructural changes caused by heating small samples for various times, up to 1000 h, at 150°C. The first change, evident at high magnification after heating for 1 h, occurred from the as cast lamellar plus fibrous form of the Ag₃Sn and Cu₆Sn₅ interdendritic eutectic phases to a particulate form. With further heating, coarsening of the two compound phases occurred, gradually rendering the Sn dendrite pattern less distinct. Due to the very rapid diffusion of Cu in solid Sn, the Cu₆Sn₅ phase coarsened most rapidly, growing from its originally finely divided (200 nm) size in the ternary eutectic to form many particles up to 3 m m or more in size in a time of 100 h. At that time, nearly 50% of the total Cu was contained in these particles. The Ag₃Sn phase coarsened more slowly. Approximate measurements of average particle size as a function of time suggested that coarsening occurs by Ostwald ripening, controlled by diffusion in the Sn phase.     

Composition and Crystalline Structure of Ternary Phases in the Ta–Ni–Al System

Russian Journal of Non-Ferrous Metals - The composition and crystal structure of compounds produced by self-propagating high-temperature synthesis (SHS) from the 5Ta–2Ni–3Al (at %)...     

Damage Assessment of A356 Al Alloy Under Ratcheting–Creep Interaction

Metallurgical and Materials Transactions A - The aim of this report was to examine the influence of asymmetric cyclic stress on the ratcheting behavior of A356 Al alloy with special emphasis on its...     

A Study on Hot Tearing Susceptibility of Al–Cu,Al–Mg,and Al–Zn alloys

The present investigation deals with the hot tearing susceptibility of A206, A518, and A713 alloys. The hot tearing tests of the mentioned alloys were conducted at three different pouring temperatures using sand mold casting. Metallic cores designed to facilitate constrained radial contraction of the aforementioned alloys were used for casting. Macroscopic cracks were found in all the samples except in A518 alloy. It was observed that pouring temperatural and grain size have significant effect on crack susceptibility. Among the investigated alloys, A713 was found to be extremely prone to hot tearing. The microstructure characteristics of the alloys were studied using optical and scanning electron microscopy. Relationships between the pouring temperature, grain size and crack lengths of the alloys were also established.     

Kinetics of discontinuous precipitation and dissolution in Cu–Ag alloys

The kinetics of discontinuous precipitation and dissolution of the cellular precipitate have been studied in Cu-3 at.% Ag and Cu-4 at.% Ag alloys. The growth rates of the cells were measured using optical microscopy. The interlamellar spacings of the primary cells and compositions of the depleted matrix were measured using scanning electron microscope and X-ray diffraction, respectively. The Cu–Ag alloys were observed to decompose into a lamellar structure consisting of alternate lamellae of the α (Cu-rich) and β (Ag-rich) phases when a solid solution of the alloy was aged below the solvus temperature. The rod shaped morphology of the β phase dispersed in the matrix of α was observed at all temperatures. The primary cell growth data were analysed using the theories of Cahn, Hillert, Sundquist, Turnbull and Petermann and Hornbogen. From the diffusivity values, it has been shown that the growth of primary cells occurs by the diffusion of Ag along the grain boundaries. The results are consistent with the diffusivity values reported in the literature in the same temperature range.The discontinuous dissolution of the primary cells occurred above the solvus temperature as well as 30–40 K below it. The dissolution occurred primarily at the prior positions of grain boundaries as well as at the primary cells intersection, at least in the initial stages of dissolution. The discontinuous dissolution occurred by the diffusion of Ag along the interface boundary between the primary and dissolution cells. The diffusivity and mobility values obtained during dissolution are one order of magnitude smaller than those obtained for the discontinuous precipitation. This has been explained by volume diffusion ahead of the interface and not all of the free energy being used to drive the interface boundary.     

Effect of Cooling Rate and Neodymium Addition on Beta Intermetallic Phase of Al–Fe–Si Ternary System

Aluminium silicon alloys are widely used in automotive industry and other structural application. However, the presence of high content of iron element in Al–Si alloys lead to precipitation of beta intermetallic phase that has a detrimental effect on mechanical properties. Reducing the adverse effects of β-Al₉Fe₂Si₂ precipitates can be achieved by altering their morphology by adding element modifier and increasing solidification cooling rate. In this present work, simultaneous thermal analysis was used to study the effect of cooling rate (5, 10 and 30 °C min^?1) on beta phase formation in Al–7Si–1Fe alloy added with neodymium at 0.3, 0.6 and 1 wt%. The beta phase precipitates were then characterized using optical microscopy and scanning electron microscopy equipped with EDS. Image analysis results showed the reduction in size of beta intermetallic phase as a result of the rare earth addition. Further analysis also showed the refinement of eutectic silicon.     

Experimental Investigation on Adhesive Wear Behavior of Al–Si6Cu/Ni Coated SiC Composite Under Unlubricated Condition

This paper studies the dry sliding wear behavior of Al–Si6Cu/Ni coated SiC metal matrix composite fabricated using stir casting technique. The SiC reinforcement particles coated with Ni by electroless coating were incorporated at 10-wt% into the metal matrix. The wear behavior was studied on unlubricated pin-on-disc tribometer based on design of experiments modelled using Response Surface Methodology for various sliding parameters such as applied load, sliding velocity and sliding distance. The minimum wear rate condition and optimum condition of the parameters were detected from the developed model. The analysis of variance showed the influence of each parameter on wear rate. The confirmation experiments were done to ensure the validity of the developed regression model. The worn-out surface morphologies of the metal composite were studied using scanning electron microscope analysis. From the experimental results it was found that the parameter which influenced the wear behavior was applied load followed by sliding velocity and distance. The confirmatory experiments confirmed the RSM’s design as precise statistical model in developing regression results with less error. The surface plot of wear characteristics showed that irrespective of the conditions of sliding velocity and distance the wear rate increased on increasing the load. The wear rate exhibited a non linear relationship with sliding velocity and distance. The scanning electron microscopy revealed that higher material deformation was observed at higher load resulting in severe wear of the composite material.     

Density and Dynamic Viscosity of Sn,Sn–Ag,and Sn–Ag–Cu Liquid Lead-Free Solder Alloys

Powder Metallurgy and Metal Ceramics - Traditionally, the soldering process was carried out, applying mainly lead-based solder materials. However, the prohibition against using lead (Pb) in...     

Phase Equilibria in Liquid Metal of the Cu–Al–Cr–O System

A thermodynamic analysis of phase equilibria in the Cu–Al–Cr–O system is carried out. Thermodynamic modeling of the liquidus surface of the Cu₂O–Al₂O₃–Cr₂O₃ oxide phase diagram is performed. To describe activities of an oxide melt, the approximation of the theory of subregular ionic solutions, the energy parameters of which were determined during modeling, is used. Melting characteristics of the CuCrO₂ compound are also evaluated in the course of the calculation. Coordinates of invariant equilibria points implemented in the Cu₂O–Al₂O₃–Cr₂O₃ ternary oxide system are established by the results of the calculation. Thermodynamic modeling of interaction processes in the Cu–Al–Cr–O system in occurrence conditions of a copper-based metal melt is also performed. The temperature dependence of the equilibrium constant of the reaction that characterizes the formation of the CuCrO₂ solid compound from components of the metal melt of the Cu–Al–Cr–O system is determined. The temperature dependence for the first-order interaction parameter (by Wagner) of chromium and oxygen dissolved in liquid copper is found. The results of thermodynamic modeling for the Cu–Al–Cr–O system are presented in the form of the solubility surface of components in metal, which makes it possible to attribute the quantitative variations in the metal melt concentration with qualitative variations in the composition of forming interaction products. It is determined by the results of modeling that particles of the |Al₂O₃, Cr₂O₃|_sol.sln solid solution are formed at valuable aluminum and chromium concentrations in the copper melt of the Cu–Al–Cr–O system as the main interaction product. The results of the investigation can be interesting for improving the technology process of smelting of chromium bronzes.     

Physical simulation study of the dynamic recrystallization kinetics of an Ni–Cu–Al alloy

The influence of temperature and deformation on the dynamic recrystallization kinetics of an Ni–30Cu–3Al heat-resistant alloy has been studied on the basis of experiments using a torsion plastometer. The process is simulated and mathematical model is proposed for estimating the dynamically recrystallized grain sizes. Good agreement between the calculated and experimental data is achieved.     

Sintering Behaviour and Mechanical Properties of Al–Cu–Mg–Si–Sn Aluminum Alloy

The present study investigates the effect of compaction pressure and sintering temperature on densification response and mechanical properties of the Al–3.8Cu–1Mg–0.8Si–0.3Sn (2712) alloy. The compacts were pressed at 200 and 400 MPa and sintered at temperatures ranging from 570–630°C in vacuum (10^?6 Torr). The objective of the present work is to obtain an optimum sintering conditions for achieving higher sintered densities and mechanical properties. The effect of sintering temperature is evaluated by measuring the sintered density, densification parameter, microstructure, phase changes and mechanical properties. While a higher sintering temperature results in densification enhancement, it also leads to microstructural coarsening. Significant improvement in mechanical properties is obtained through age-hardening of sintered alloy under various ageing conditions (T4, T6 and T8).     

Microstructure evolution and densification behaviour of powder metallurgy Al–Cu–Mg–Si alloy

ABSTRACT

An Al–Cu–Mg–Si alloy was prepared by conventional press-sintering powder metallurgy using elemental Al powder. The phase transformation process of Al–Mg, Al–Si alloy and Cu during the sintering process was investigated in details. It was found that a series of phase transitions take place in the alloy to disrupt the oxide film of Al particle and enhance the densification process. The relative density of the sintered samples reached 98%. A new Al–Mg–Cu–O compound was found at the grain boundaries except the MgAl₂O₄ phase, it is speculated that the disruption of the oxide film was also associated with the other alloy compositions except for Mg. Furthermore, no detectable AlN compound was found at the grain boundary region although sintering with flowing nitrogen atmosphere, which is benefit from the high density of the green compact and the excellent wettability between the liquid phase and the aluminium.     

Effect of Zr Content on the Microstructure and Corrosion Resistance of Al–Cu–Mn Alloy

Russian Journal of Non-Ferrous Metals - In order to improve the overall properties of cast Al–Cu–Mn alloy, the effect of Zr content on the microstructure and corrosion resistance of...     

Microstructures and mechanical properties of rapidly solidified CuCr alloys

Rapidly-quenched CuCr alloys have been prepared by melt-spinning and the microstructures and mechanical properties examined as a function of alloy content and subsequent annealing treatment. Mechanical properties have been successfully measured by tensile testing on the ribbon samples and it is shown that this method is more suitable than hardness testing for a proper evaluation of the materials. An alloy containing 2% Cr has been prepared in the totally solid-solution state, whilst a 5% Cr alloy contains large chromium particles distributed uniformly throughout the ribbon and fine-grain-sized CuCr solution. These large chromium particles are deduced to arise by a uniform, primary-solidification mode prior to, and independent of, the nucleation and growth of the copper from the lower ribbon surface. The increased solid solubility obtained allows extensive precipitation and strengthening following ageing: the primary chromium particles play an important role both in strengthening and in restricting grain coarsening.