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Uniaxial tensile tests were performed on fine-grained, rolled AT33 alloy at strain rates of 1.0 × 10-4-1.0 × 10-1 s-1 and temperatures of 25-250 °C. The rolled AT33 alloy with an average grain size of 7mm was produced by cast-rolling and hot-rolling. The relative deformation mechanisms at high temperature were investigated in this study. It was found that the strain rate sensitivity increases from 0.01 at room temperature to 0.13 at 250 °C. The average stress exponent and the activation energy have been calculated to be 6.5 and 145 kJ mol-1, respectively, indicating that the dominant tensile deformation mechanism is dislocation climb-controlled creep profiting from the lattice self-diffusion. The dispersed nano-sized Mg2Sn particles in the rolled AT33 alloy increase dislocation accumulation, which not only contributes to a promising tensile strength at high temperature but also provides a high driving force for the dynamic recrystallization (DRX). It has found that DRX is mainly responsible for the obtained high tensile ductility of 76-205% at temperatures of 200-250 °C. [ABSTRACT FROM AUTHOR]

Abstract In the present work, we investigated the influence of deformation temperature on the formation of a bimodal microstructure and tensile properties of a Mg–9Al–1Zn (AZ91) alloy processed by a single pass hard plate rolling (HPR) with a thickness reduction of 55% followed by a short time annealing. Microstructural examinations by electron backscatter diffraction (EBSD) reveal that there exists a narrow deformation temperature window, i.e. it is only feasible to achieve a desired bimodal grain structure in the AZ91 alloy when HPRed at ∼350 °C. It is mainly because that partial dynamic recrystallization (DRX) occurs easily in the sample HPRed at ∼ 350 °C, facilitating the formation of a bimodal microstructure consisting of coarse un–recrystallized grains (>∼70 μm) and fine recrystallized grains (<∼5 μm). In contrast, reducing deformation temperature to ∼300 °C results in a coarse unrecrystallized microstructure containing substantial sub structure, while elevating the deformation temperature to ∼400 °C leads to an almost uniform recrystallized grain structure. Especially, the formation mechanism for the bimodal grain structure at the optimum deformation temperature is explored in terms of Schmidt factors analysis for basal slips (SF basal ) for grains of different size scales. Moreover, the 350 °C HPRed AZ91 sample exhibits a better combination of strength (ultimate tensile strength = ∼374 MPa) and ductility (elongation = ∼19.6%), as compared to the 300 and 400 °C samples. It is mainly attributed to the typical bimodal grain structure and the relatively high SF basal featured by the fine recrystallized grains as well as the nanometer spherical particles distributing in fine grain interiors. Graphical abstract Image 1 Highlights • A bimodal grain structure of Mg–9Al–1Zn alloy was achieved by tailoring rolling temperature during hard–plate rolling (HPR). • The formation of bimodal microstructure was explored in terms of Schmidt factors analysis for basal slips (SF basal ). • The formation of bimodal grain structure generated a simultaneous improvement of strength and ductility. [ABSTRACT FROM AUTHOR]

In the present work, Mg-9Al-1Zn-0.4Sn (AZT910) magnesium alloy sheets with a fine-grained structure (∼5 μm) and tilting basal texture were prepared by a 16-passes rolling process. Effect of tensile directions on properties and microstructural evolutions of the AZT910 alloy sheet at different temperatures, i.e. room temperature, 200 and 300 °C, respectively, were investigated by using three kinds of tensile specimens (rolling direction (RD), transverse direction (TD) and 45° towards RD). Experimental results showed that tensile properties exhibited a strong dependence on tensile directions at room temperature and 200 °C, while a negligible dependence at 300 °C. The anisotropic tensile properties imply that the deformation system of rolled AZT910 sheet consists of basal and non-basal slips at room temperature, and is a combination of basal slip, non-basal slip and grain boundary sliding/rotation (GBS) at 200 °C. The decrease of intensity and spreading of basal poles during tensile test and isotropic tensile properties indicates that GBS becomes the dominate deformation mechanism at 300 °C. The present work provides reference for the study of deformation behavior of novel superplastic magnesium alloy, and hence is of great significance for further application of wrought magnesium alloy. [ABSTRACT FROM AUTHOR]

The coarse segregative eutectic phases, emerged in the twin roll casting (TRC) process of Mg strips, which cannot be resolved solely by controlling the processing variables or post heat treatment, are detrimental to the subsequent rolling deformation. Considering it, we introduce the pre-rolling steps on the TRC Mg-4Al-2Sn-1Zn (ATZ421) alloys, which is expected to facilitate the dissolution of these segregative phases by increasing distortion of crystal lattices and rolling stress, and further investigate the effect of a single pass or two passes pre-rolling on the microstructure evolution and tensile properties. It indicates that the pre-rolled alloy with two passes presents more uniform precipitates and higher twinning density in comparison with that using a single pass. The uniform distribution of precipitates in two passes pre-rolling is due to the increase in density of dislocations and deformed twins, which results in more distortion of crystal lattices with more stored energy, facilitating the diffusion of solutes. Moreover, the pre-rolling of two passes introduces more rolling stress into Mg matrix, which is beneficial for the crush of coarse eutectic phases, and further accelerates the sufficient dissolution of second phases. After the subsequent rolling and annealing processes, the sheet with pre-rolling deformation of two passes shows finer microstructure, which mainly benefits from the pinning effects of uniform nano-sized precipitates. As a result, the annealed sheet with two-pass pre-rolling deformation exhibits an advantageous combination of high strength and high ductility with fine microstructure, showing an ultimate tensile strength of ~297 MPa, a yield strength of ~ 205 MPa and an elongation of 25.0%. This work provides an effective method of dissolving the coarse segregative phases in the TRC Mg alloys with significant potential for industrial production. [ABSTRACT FROM AUTHOR]

In the present study, Mg-6Zn-1Zr (ZK60) alloy with a homogeneous fine-grained structure (~5 µm) was produced by hot extrusion. The influence of temperature on tensile properties anisotropy and the associated change in deformation mechanisms in the range of 25–275 °C of the fine-grained ZK60 alloy were investigated. Under room temperature, the fine-grained ZK60 alloy exhibited a high tensile strength of ~269–327 MPa and high ductility of ~15–39% when tested at three different directions, indicating a high anisotropy. With increasing testing temperature to 150 °C and further to 275 °C, the alloy showed a gradual decrease in anisotropy. Especially, the fine-grained ZK60 alloy exhibited superplasticity of ~376–434% when tested at 275 °C, which should be due to the increasing role of grain boundary sliding (GBS), as the strong basal texture associated with room temperature deformation became almost random at elevated temperatures. Moreover, the abrupt decrease in tensile anisotropy and associated change in texture with increasing temperature correlates closely to the transformation of deformation mode from a dislocation-dominated behavior to a GBS-mediated one. [ABSTRACT FROM AUTHOR]

The effects of doping atoms (X) on the uniaxial deformation and universal ductility of Mg47X1 are investigated. A first-principles “design map” in regard to the generalized stacking-fault energy (GSFE) provides a database for new Mg alloys design. The calculation and analysis of GSFEs here, considering the weighting of each slip system, solubility of alloying elements and ductility capacity, provide a basis for further understanding and controlling alloying elements, which will inspire developing new Mg alloys with tailored properties. [Copyright &y& Elsevier]

Abstract: Uniaxial compression tests were performed on an extruded Mg–6Al–3Sn (AT63) alloy with a dual basal texture, along the extrusion direction (ED), transverse direction (TD) and normal direction (ND). Unlike the single basal texture commonly seen in rolled Mg alloys, for which either extension or contraction twinning is favored in one compression, the dual basal texture appreciates both extension and contraction twinning. Nevertheless extension and contraction twinning display different activities among the three compressions. The results suggest that extension twinning propagates largely for ED compression while it displays limited propagations for TD and ND compressions, although it nucleates at the onset of plasticity for all the three compressions. In contrast, contraction twinning nucleates early and widely for TD and ND compressions while it is largely suppressed for ED compression. It is the wider propagations of extension twinning and belated contraction twinning that result in a larger drop and a higher peak in the strain hardening curve for ED compression. Our results shed some light on deformation mechanisms of the Mg alloys consisting of multiple texture components. [Copyright &y& Elsevier]

Abstract: Plane strain compressions were conducted on a rolled Mg–6Al–3Sn (AT63) alloy plate along the rolling direction (termed in-plane compression, IPC) and normal direction (termed through-thick compression, TTC), respectively. Deformation behaviors (mechanical response, microstructure evolution and macrotexture development) of each plane strain compression were compared against those of equivalent uniaxial compression (UC), and deformation mechanisms of IPC and TTC were investigated in detail. It has been found that the IPC with transverse constraint exhibits enhanced basal slip and retarded extension twinning with respect to the corresponding UC. However, the IPC with normal constraint transforms the main deformation mechanisms (i.e., extension twinning and basal slip) into prismatic slip and directional pyramidal slip. The TTCs, no matter with rolling or transverse constraint, suppress basal slip dramatically and cause directional contraction twins and directional pyramidal slip. The differences in deformation mechanisms between the plane strain compression and the corresponding UC are explained in relation to Schmid factor and strain directionality. Our results shed light on the deformation mechanisms of Mg alloys during plane strain compressions. [Copyright &y& Elsevier]

Schmid factors (m) for typical slip modes (basal 〈a〉, prismatic 〈a〉, pyramidal 〈a〉 and 〈c + a〉 slips) and twinning patterns ( and twins) were systematically calculated in hexagonal close-packed Cd, Zn, Mg, Zr, Ti and Be. A monotonic effect on m-values was presented for pyramidal 〈a〉 and 〈c + a〉 slips, and and twinning patterns with decreasing c/a ratio. The results calculated herein were used to characterize deformation behaviors and provide essential data for anisotropic feature analysis. [ABSTRACT FROM AUTHOR]

Abstract: The plastic deformation behavior of as-cast Mg–3Sn–1Zn (TZ31) alloy was investigated at room temperature, which exhibits strong strain hardening ability (i.e. n=0.55 and H c=3.62) and high elongation (ε p=19.1%). The generalized stacking fault (GSF) energy of TZ31 alloy is reduced owing to dopings of Sn and Zn atoms, which is beneficial to improving activity of basal slip, activation of non-basal slips and formation of numerous deformation twins. The high density of twins significantly restricts dislocation motion, leading to strong strain hardening ability of the TZ31 alloy. Results obtained here will shed some light on deformation mechanisms of Mg–Sn–Zn alloys, critical to the development of new high-plastic magnesium alloys. [Copyright &y& Elsevier]

The Schmid factors for four slip systems (basal 〈a〉, prismatic 〈a〉, pyramidal 〈a〉 and 〈c + a〉 slips) and two twinning patterns ( and twins) were systematically calculated in magnesium as a function of angles between the c-axis and the loading direction. The results generated in this study can be effectively used to interpret deformation behaviors, including describing the flow stress and characterizing deformation behaviors, in magnesium and some hexagonal metals whose c/a axial ratios approximate to that of Mg (1.624). [ABSTRACT FROM AUTHOR]

Abstract: The deformation mechanisms for rolled Mg–3Al–3Sn alloys were strongly dependent on grain sizes at room temperature. For grain sizes of ∼6–22μm, the deformation in tension was mainly dominated by dislocation-slip, which, however, turned to be mediated by deformation-twinning for those of ∼22–41μm. Moreover, as deformation proceeded, Hall–Petch slopes for slip-controlled-plasticity (k S) decreased gradually due to continuous activation of non-basal slips, while that for twinning-mediated-plasticity (k T) increased rapidly owing to increase in twin number and density, corresponding to grains below and above the medium-size of ∼22μm respectively. [Copyright &y& Elsevier]

Metal-ceramic composites generally exhibit limited strength-plasticity synergy due to pronounced difference in elastic and plastic deformation between "soft phase" and "hard phase", bottlenecking their applications. This work proposes a novel microstructure design concept using refractory metals and intermetallics to offer compromises between "soft phase" and "hard phase". A cost-effective fabrication method was used to produce 70 vol% (TiC + Al 6 MoTi + Mo)/Al cermet. The cermet is composed of submicron-TiC, micron-Al 6 MoTi and nano-Mo particles separated by Al in homogeneous microstructure. This multiple length-scale microstructure could delocalize stress concentration, enhance work hardening and deformation compatibility in cermet, resulting in unprecedentedly enhanced strength-plasticity synergy. Ultimate compressive strength, plastic strain and product of strength and plasticity of (TiC + Al 6 MoTi + Mo)/Al at room temperature and 573 K respectively are 1227 MPa, 6.9%, 7445 MPa·% and 781 MPa, 15.0%, 10021 MPa·%, which are increased by ~30%, ~25%, ~60% and ~37%, ~9%, 41% respectively compared with those for traditional 70 vol% TiC/Al. This work opens new perspectives for the design and application of metal-ceramic composites with high strength and plasticity synergy. [Display omitted] • A new strategy is proposed for develop metal-ceramic composites with multiple length-scale microstructure. • This multiple length-scale microstructure could enhance deformation compatibility. • 70 vol% (TiC + Al 6 MoTi + Mo)/Al cermet with unprecedentedly enhanced and plasticity synergy were fabricated. [ABSTRACT FROM AUTHOR]

TiAl-5wt.%Ti 2 AlC-3wt.%Mn composites reinforced by the addition of Mn and in situ synthesized Ti 2 AlC nanoparticles with a novel microstructure were fabricated. The microstructure and compressive properties of the fabricated composites were thoroughly investigated. The interface between the nanoparticles and the TiAl matrix maintained a very small mismatch and exhibited a stable combination, leading to noticeable grain refinement in the fabricated composites. Furthermore, the yield strength, maximum compressive strength, fracture strain, and strength-ductility balance of the TiAl-5wt.%Ti 2 AlC-3wt.%Mn composites increased by 30.7%, 10.1%, 5.5%, and 9.9%, respectively, compared with those of the TiAl alloy. The mechanisms by which the properties of the composites were improved mainly thermal mismatch strengthening, Orowan strengthening, grain refinement strengthening, and solid solution strengthening. • In-situ Ti 2 AlC particles and Mn evolved TiAl alloy into a refined microstructure. • The interface between the TiAl matrix and nanoparticles exhibited a stable combination. • Toughness and strength of TiAl composites were significantly elevated by 9.9% and 30.7%. • The dominant ones were the thermal mismatch and the Orowan strengthening mechanism. [ABSTRACT FROM AUTHOR]