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The effect of ultrafine-grained structure formation in Mg-Zn-Zr alloy ZK60 on its mechanical response was investigated at strain rates ranging from quasi-static to dynamic regimes. The study demonstrated that the strength characteristics of the material rise significantly with increasing strain rate, while its ductility is reduced. These effects are particularly pronounced in the dynamic loading r
IF steel sheets were processed by conventional symmetric and asymmetric rolling (ASR) at ambient temperature. The asymmetry was introduced in a geometric way using differential roll diameters with a number of different ratios. The material strength was measured by tensile testing and the microstructure was analyzed by optical and transmission electron microscopy as well as electron backscatter dif
The present study has clarified the roles of dislocation slip and twinning as the deformation mechanisms in magnesium alloys, as well as the effect of grain size on their relative contributions. The details of these mechanisms were studied by monitoring acoustic emission (AE) in conjunction with a novel signal categorization technique in Mg alloy ZK60. Through the analysis of AE time series the se
Materials having bimodal grain structures are known for the good balance of strength and ductility. However, methods for their fabrication often lack the control of such structure characteristics. In this work, the principles of "harmonic" structure fabrication allowing to control both topology and scale of the bimodal structure heterogeneity have been concisely formulated. The feasibility to form
Fatigue performance under axisymmetric push-pull loading of a magnesium alloy Mg-6Zn-0.5Zr (ZK60) after processing by integrated extrusion and equal-channel angular pressing was investigated. Such processing was shown to nearly treble the endurance limit of the alloy, raising it to 160 MPa. It was established that the high-cycle fatigue performance of ZK60 is primarily controlled by dislocation su
High-pressure torsion was used for the deformation processing of high-purity aluminum (4N-Al), while high-resolution electron-backscatter diffraction was used for the analysis of evolution of qualitative and quantitative microstructural characteristics. This study reveals a rather full picture of microstructure evolution in the high stacking fault energy fcc material and makes a continuous link be
In the present work, effects of loading scheme and strain reversal on structure and hardness evolution have been studied by using high pressure torsion (HPT) and twist extrusion (TE) techniques. High purity aluminium (99.99%) was processed at room temperature up to a maximum total equivalent strain of εmax ≈ 8 by TE, and HPT in monotonic and reversal deformation modes with strain increment Δεmax =
In the present study, the effects of kinematic and geometric asymmetries in rolling during multi-pass processing of IF steel are examined. The theoretical investigation by final element simulations and experimental investigations by means of electron-backscatter diffraction analysis and tensile tests suggest that asymmetric rolling increases the total imposed strain compared to symmetric rolling,
Asymmetric rolling (ASR) is a potential process to reach better grain refinement than in conventional rolling, thus, can lead to better mechanical properties. It is not known, however, how the introduction of a shear component will change the ideal orientations of the textures, and consequently, the evolution of plastic anisotropy. To understand the effect of the added shear on texture evolution i
The effect of additional shear on the asymmetric rolling (ASR) of an interstitial-free (IF) steel was studied by modeling and experiments. The asymmetry was introduced by making one roll idle. A 66 pct of total thickness reduction was performed in 6 passes with less than 16 pct reduction per pass. ASR was performed in two ways: monotonically and by rotating the sheet between passes by 180 deg arou
The paper demonstrates the feasibility of upscaling of severe plastic deformation (SPD) techniques using an integrated process that combines conventional extrusion and equal channel angular pressing in a single processing step. The process was applied for production of magnesium ZK60 bars 16 mm in diameter and up to 4 m in length. The processed material exhibited an excellent balance of strength a
Bimodal grain structure was fabricated in a 99.99% purity aluminium by high pressure torsion at ambient temperature in reversal deformation mode at a strain amplitude Δε = 1, strain rate ̇=1.1×10 -1s-1 and hydrostatic pressure P = 5 GPa. Enhanced boundary mobility due to the high purity of the aluminium and homologous temperature coupled with reversal simple shear deformation are found to be respo
It was demonstrated in this work that the corrosion rate of Mg alloy ZK60 can be reduced through the use of an integrated process of extrusion and equal channel angular pressing concomitant with increased strength. The improvement in corrosion resistance, as measured by electrochemical experiments and immersion tests in NaCl electrolytes, was correlated with both grain refinement and the redistrib
As-received hot-rolled 5.6 mm thick IF steel sheet was symmetrically/ asymmetrically cold rolled at room temperature down to 1.9 mm. The asymmetric rolling was carried out in monotonic (an idle roll is always on the same side of the sheet) and reversal (the sheet was turned 180° around the rolling direction between passes) modes. Microstructure, texture and mechanical properties were analysed. The
Among the known severe plastic deformation (SPD) techniques, one particular group can be defined as SPD processing of thin samples. Their distinctive feature is that one of the sample dimensions, namely the thickness, is much smaller than the other two dimensions. Examples include High Pressure Torsion and two recently developed techniques: the Cone-Cone Method and the High Pressure Tube Twisting.
In the present work, effects of loading scheme and strain reversal on structure evolution are studied by using high pressure torsion (HPT) and twist extrusion (TE) techniques. High purity aluminum (99.99%) was processed at room temperature up to a total average equivalent strain of ∼4.8 by TE and HPT with two deformation modes: monotonic and reversal deformation with a step of 12° rotation. It was
The evolution of texture in pure aluminum subjected to monotonous and reversal deformation in high-pressure torsion was first clarified. In a low-strain regime the texture development is similar for both deformation modes, while significantly different behavior is observed at high strain levels. The monotonously deformed materials showed typical torsion textures. In contrast, strain reversal resul
High purity Al (99.99%) was subjected to severe plastic deformation through twist extrusion at room temperature. Microstructures were examined for 1 pass and 4 passes on the cross section perpendicular to the longitudinal axis of billets using optical microscopy and electron back scatter diffraction analysis. It was shown that a vortex-like material flow was observed on the cross section and this
High purity Al (99.99%) is subjected to severe plastic deformation (SPD) at room temperature using a process of twist extrusion (TE). The microstructure evolution and the related change in microhardness are examined with respect to imposed strain. It is shown that subgrains develop after the first TE pass with a size of ∼1.6 μm and this size remains essentially the same for further application of
