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The magnesium AZ31 alloy was swaged with rotary pressure with the aim of redefining the microstructure and improving mechanical and fatigue properties. The rotary swaging process and subsequent ageing improved the yield stress in tension and compression. In the present study, the investigation was focused on fatigue behaviour. The samples were cycled in a symmetric regime with a frequency of 35 Hz. A dependence of the stress amplitude on the number of cycles up to the fracture was estimated. The microstructure of the samples and fracture surfaces was analysed with a scanning electron microscope. The fatigue process was influenced by the pronounced texture formed in the swaging process. The fatigue properties of the swaged samples improved substantially—the endurance limit based on 107 cycles was approximately 120 MPa—compared to those of the cast alloy. The analysis of the fracture surfaces showed a transcrystalline fatigue fracture. [ABSTRACT FROM AUTHOR]

Magnesium alloy QE22 (nominal composition 2 wt % Ag, 2 wt % mixture of rare earth elements, balance Mg) was reinforced with 5 vol % Saffil fibers and 15 vol % SiC particles. The hybrid composite was prepared via the squeeze cast technique. The microstructure of the monolithic alloy and composite was analyzed using scanning electron microscopy. Elastic modulus was measured at room temperature and modeled by the Halpin-Tsai-Kardos mathematical model. The strengthening effect of fibers and particles was calculated and compared with the experimentally obtained values. The main strengthening terms were determined. Fracture surfaces were studied via scanning electron microscope. While the fracture of the matrix alloy had a mainly intercrystalline character, the failure of the hybrid composite was transcrystalline. [ABSTRACT FROM AUTHOR]

Deformation behaviour of rolled AZ31 sheets that were subjected to the accumulative roll bonding was investigated. Substantially refined microstructure of samples was achieved after the first and second pass through the rolling mill. Sheets texture was investigated using an X-ray diffractometer. Samples for tensile tests were cut either parallel or perpendicular to the rolling direction. Tensile tests were performed at temperatures ranging from room temperature up to 300 °C. Tensile plastic anisotropy, different from the anisotropy observed in AZ31 sheets by other authors, was observed. This anisotropy decreases with an increasing number of rolling passes and increasing deformation temperature. Grain refinement and texture are the crucial factors influencing the deformation behaviour. [ABSTRACT FROM AUTHOR]

The amplitude-dependent internal friction of continuously-cast and rolled AZ31 magnesium alloy was measured in this study. Samples were annealed and quenched step by step; immediately after the treatment, the amplitude dependence of the logarithmic decrement was measured. Changes in the microstructure due to thermomechanical treatment were reflected in changes in the damping. Internal friction is influenced by the dislocation substructure and its modification due to solute atoms migration, microplastic deformation, and twins' formation. Internal friction in the rolled sheets is affected by the rolling texture. [ABSTRACT FROM AUTHOR]

New Mg-3Zn-2Ca magnesium alloy was prepared using different processing techniques: gravity casting as well as squeeze casting in liquid and semisolid states. Materials were further thermally treated; thermal treatment of the gravity cast alloy was additionally combined with the equal channel angular pressing (ECAP). Alloy processed by the squeeze casting in liquid as well as in semisolid state exhibit improved plasticity; the ECAP processing positively influenced both the tensile and compressive characteristics of the alloy. Applied heat treatment influenced the distribution and chemical composition of present intermetallic phases. Influence of particular processing techniques, heat treatment, and intermetallic phase distribution is thoroughly discussed in relation to mechanical behavior of presented alloys. [ABSTRACT FROM AUTHOR]

AX41 magnesium alloy was reinforced with short Saffil fibers using squeeze cast technology. Samples of the composite were deformed in compression at elevated temperatures. The work hardening rate as a function of the flow stress in the matrix was investigated. A model taking into account two hardening and two softening processes was used for analyzing of experimental curves. Parameters of the model follow different temperature dependences. Possible hardening and softening processes are discussed. [ABSTRACT FROM AUTHOR]

AZ91 and ZE41 matrix composites reinforced with short δ-alumina fibres (Saffil®) were manufactured by the squeeze casting technology. The structure of composite materials consisted of short δ-alumina fibres (approximately 20 vol.%) distributed planar-randomly within the matrix. Compression tests on cylindrical composite samples were carried out at temperatures between 20 and 300 °C. Results obtained revealed that the flow stresses of the composites are substantially higher than those of unreinforced alloy at lower temperatures up to 200–250 °C, while at higher temperatures the influence of fibres is not significant. Different contributions to the strength of composites were evaluated. The shear stresses at the fibre–matrix interface were of the greatest importance in this regard, though the contributions resulting from the dislocation density increase. Thermal stresses are also significant. [Copyright &y& Elsevier]

This paper describes the influence of thermal cycling on the damping behaviour of composites with Mg matrix and two contents (26.0 and 34.1 vol.%) of Saffil short fibres. The composites were prepared by squeeze casting. The logarithmic decrement, as a characteristic of the process responsible for the damping behaviour, was measured after ten thermal cycles between room temperature and an upper temperature. The upper temperature was varied within the range from 100 to 450°C. The strain dependence of the logarithmic decrement can be divided into two regions. A region of strain amplitude independent damping at low strains is followed by a region with amplitude dependent damping at higher strains. The damping level in the strain amplitude independent region depends weakly on the upper temperature of the cycle whereas the values of the logarithmic decrement in the strain amplitude dependent region depend very sensitively on the upper temperature of cycles. The observed experimental data can be explained considering creation of new dislocations during thermal cycling following recovery processes at higher upper temperatures of the cycle. [ABSTRACT FROM AUTHOR]

Stress-relaxation tests were performed during plastic deformation at room temperature of three magnesium Mg–Li alloys reinforced with 10 vol% of short Saffil fibers. For comparison, the composite with the Mg matrix was studied. The time dependencies of the stress decrease were analyzed with the aim to determine the activation volume and the main types of thermally activated processes occurring during plastic flow. The Mg4Li matrix alloy exhibited the hcp structure, while the composite with the Mg12Li matrix alloy had the bcc structure. The third alloy, Mg8Li, combined both phases, hcp and bcc. The stress acting in the matrix was divided into two components: the internal stress and the effective stress. Activation volume and stress-sensitivity parameters were determined as a function of effective stress and strain. While the values of the activation volume depending on the effective stress lay on one "master" curve, the strain dependence was different for all materials. The main thermally activated process in the hcp structure was the dislocation motion in the noncompact planes, while in the bcc structure, massive recovery processes connected with an increase in dislocations were identified. [ABSTRACT FROM AUTHOR]

An extruded magnesium AZ31 magnesium alloy was processed by rotary swaging (RSW) and then deformed by tension and compression at room temperature. The work-hardening behaviour of 1–5 times swaged samples was analysed using Kocks-Mecking plots. Accumulation of dislocations on dislocation obstacles and twin boundaries is the deciding factor for the strain hardening. Profuse twinning in compression seems to be the reason for the higher hardening observed during compression. The main softening mechanism is apparently the cross-slip between the pyramidal planes of the second and first order. A massive twinning observed at the deformation beginning influences the Hall-Petch parameters. [ABSTRACT FROM AUTHOR]

Amplitude dependent internal friction (ADIF) was measured in three AZ magnesium alloys. Two types of experiments were performed: ADIF was measured step by step with the increasing strain amplitude and ADIF was measured after predeformation of samples in torsion. All experiments were done at room temperature. The quality factor was used as a measure of internal friction (IF). The quality factor decreased in the region of smaller amplitudes, and approaching some critical amplitude, εcr, rapidly increased. This critical amplitude increased with increasing maximum strain amplitude and predeformation of samples up to ~6%. Such behavior can be explained by considering mobile solute atoms, which may migrate along the dislocation line in the region of smaller amplitudes and perpendicular to the dislocation line in the region of higher amplitudes. A competition between dragging and depinning of solute atoms with dislocation lines may very well explain the measured dependencies. [ABSTRACT FROM AUTHOR]

An ultrafine-grained EN AW 6082 aluminum alloy was prepared by continuous serve plastic deformation (i.e., thermo-mechanical equal channel angular pressing (ECAP)–Conform process). A miniaturized tensile testing technique was used for estimating local mechanical properties with the aim to reveal the inhomogeneity of elastic and plastic properties in a workpiece volume. These inhomogeneities may appear due to the irregular shear strain distribution in a Conformed wire. Miniaturized samples for tensile testing were cut from the Conformed workpiece. Elongation of miniaturized samples was measured with a 2D digital image correlation technique as the optical extensometer. Tensile test characteristics, such as the yield strength and ultimate tensile strength, were consequently compared with results of conventional and hardness tests. The microstructure of Conformed bars was studied in the cross-section perpendicular and parallel to the extrusion direction using scanning electron microscope (SEM) and electron backscatter diffraction (EBSD) analysis. The microstructure of samples exhibits pronounced inhomogeneity, which is reflected by the hardness and tensile test results. Estimated distinctions between peripheral and central parts of the Conformed wires are probably a consequence of the significant strain differences realized in the upper and bottom wire parts. [ABSTRACT FROM AUTHOR]

An AX52 magnesium alloy (nominal composition Mg-5Al-2Ca in w.%) was submitted to equal channel angular pressing (ECAP) using processing route A; 1–8 passes through the ECAP tool were applied. The thermal conductivity of the ECAP samples was measured using a flash method in the temperature interval from room temperature up to 350 °C. The microstructure and texture of the samples were studied by light and electron microscopy. The severe plastic deformation, realized by the ECAP, influences the thermal properties of the alloy. The possible microstructural parameters determining the thermal conductivity were analyzed. New dislocations, the grain, phase boundaries, and texture of the samples may perceptibly change the thermal properties. [ABSTRACT FROM AUTHOR]

AX61 magnesium alloy was reinforced with short Saffil fibres using squeeze cast technology. Samples were cut from the casting in two directions: parallel and perpendicular to the fibre plane. Samples were deformed in compression at various temperatures from room temperature to 300 °C. Various strengthening mechanisms such as load transfer, increased dislocation density, Orowan and Hall–Petch strengthening were analysed. During deformation, the stress relaxation tests were subsequently performed. The relaxation curves were evaluated with respect to Li and Feltham equations with the aim to find stress components in matrix and parameters of the thermally activated process(es). [ABSTRACT FROM AUTHOR]

This recent study deals with the optimization of the mechanical performance of Grade 2 and Grade 4 titanium with Conform severe plastic deformation (SPD) processing and subsequent rotary swaging. A comprehensive study of the materials behaviour and characterisation during and after processing is given by (finite element method - FEM) numerical simulation, microscopy methods and mechanical testing. The mechanical and fatigue properties are discussed in terms of texture and microstructure evolution. It is shown that the combination of Conform SPD and rotary swaging is a promising technique for economically reliable, high-gain production of titanium alloys fulfilling requirements for biomedical applications. Such a processing can improve the mechanical properties of the unalloyed titanium to the level of the commonly used Ti-6Al-4V. [ABSTRACT FROM AUTHOR]

The microstructure and mechanical properties of AZ31 alloy rods are investigated after rotary swaging in five successive steps. The microstructure is analyzed using light microscopy and electron backscattered diffraction. Swaged samples exhibit refined microstructure. Tensile and compression tests are conducted at room temperature. The yield stress and the ultimate stress are determined. Acoustic emission is measured in situ during straining. Deformation mechanisms are closely linked to twinning and dislocation slip in non‐basal planes. [ABSTRACT FROM AUTHOR]

Commercially available AZ31 magnesium alloy was four times extruded in an equal rectangular channel using three different routes (A, B, and C). Micro tensile deformation tests were performed at room temperature with the aim to reveal any plastic anisotropy developed during the extrusion. Samples for micro tensile experiments were cut from extruded billets in different orientations with respect to the pressing direction. Information about the microstructure of samples was obtained using the electron back-scatter diffraction (EBSD) technique. Deformation characteristics (yield stress, ultimate tensile stress and uniform elongation) exhibited significant anisotropy as a consequence of different orientations between the stress direction and texture and thus different deformation mechanisms. [ABSTRACT FROM AUTHOR]

Accumulative roll bonding (ARB) is one of the methods of severe plastic deformation which is relevant for industrial production of sheets. While mechanical properties of several magnesium alloys subjected to the ARB process have been studied, the physical properties have been reported only for some magnesium alloys. These properties are influenced by the texture developed during the ARB process and the temperature load. In the presented contribution, we studied thermal conductivity of an AZ31 magnesium alloy after one and two passes through the rolling mill. Thermal diffusivity was measured with the laser-flash method in the temperature range between 20 and 350 °C. Thermal conductivity depends on the number of rolling passes. The microstructure and texture of sheets are significant factors influencing thermal properties. [ABSTRACT FROM AUTHOR]

An extruded magnesium AZ31 magnesium alloy was processed by rotary swaging (RSW) and then deformed by tension and compression at room temperature. The work-hardening behaviour of 1-5 times swaged samples was analysed using Kocks-Mecking plots. Accumulation of dislocations on dislocation obstacles and twin boundaries is the deciding factor for the strain hardening. Profuse twinning in compression seems to be the reason for the higher hardening observed during compression. The main softening mechanism is apparently the cross-slip between the pyramidal planes of the second and first order. A massive twinning observed at the deformation beginning influences the Hall-Petch parameters.