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The contribution of recrystallization and grain growth to the texture evolution in AZ31 alloy and a modified version AZ31+0.5 wt.% Ca was investigated utilizing a multi-step annealing process. The results showed that the addition of Ca triggered a considerable texture modification by increasing the texture spread and decreasing the overall texture intensity. This effect was found to be temperature dependent. When the annealing temperature remained lower than 450 °C, a weak double peak texture with large basal pole tilt towards the RD was formed. This is correlated to microstructure observations of a large number of Ca-containing nano-sized particles that seemed to suppress grain growth below 450 °C, which stabilized the weak recrystallization texture. This favorable texture was lost upon annealing at higher temperatures. In AZ31, recrystallization nuclei were found to preserve the orientation of their deformed parents, which offered limited potential to optimize the texture via annealing treatments. Grain growth of recrystallized grains resulted in a distinct sheet texture transition from a double-peak to a single-peak basal texture. Aspects of grain boundary energy and grain topology are discussed to explain the growth advantage of the sharp basal component over other orientations. [ABSTRACT FROM AUTHOR]

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A sandwich structure of Mg alloy bulk consisted of two types of texture was fabricated by pre-twinning deformation. Its mechanical response and work hardening behavior during uniaxial compression were deeply analyzed to investigate the competition mechanism between basal slip and detwinning. Results showed that pre-twinning layer was a soft region. It undertook more than half of the strain by one third of the volume fraction of the bulk at the beginning of deformation. Slip behavior was significantly enhanced by detwinning and it took a more important role to coordinate local strain. Texture bonding promoted slip behavior in the grains exhibited "hard" orientations. Activation of detwinning behavior in pre-twinning region was mainly depended on basal slip behavior of their parents. [ABSTRACT FROM AUTHOR]

Abstract The effect of Zn (0–1 wt%) content on the aging behavior and mechanical properties of Mg 8Al 2Sn-xZn alloys have been investigated. The results indicated that addition of Zn promoted the age-hardening response and precipitation of the Mg 17 Al 12 phases through high grain boundary migration and the increase of the nucleation rate of Mg 17 Al 12 phases. The proportion of discontinuous precipitation zone in the Mg 8Al 2Sn 1Zn alloy was 37%, which was two times larger than that in the Mg 8Al 2Sn alloy without Zn. The discontinuous precipitation phases grew fast and were not suppressed by nano-size Mg 2 Sn phases. Both continuous and discontinuous precipitates were refined in the as-aged alloys with the addition of Zn. According to the yield strength calculation, fine precipitates with high density more effectively enhanced the strength in Mg 8Al 2Sn 1Zn alloy. The yield strength of the Mg 8Al 2Sn 1Zn alloy was increased by 24% after the aging treatment. The peak-aged AZT812 alloy exhibited mechanical properties that included a yield strength, an ultimate tensile strength and an elongation of 296 MPa, 408 MPa and 7%, respectively. [ABSTRACT FROM AUTHOR]

Abstract The microstructure and texture characteristics of commercial pure Ti after friction stir processing (FSP) with a slow rotation speed were studied. The shoulder friction zone (SFZ) which did not exist in the FSPed pure Ti with normal rotation speed (> 250 rpm) was observed in the sample treated with a slow rotation speed of 180 rpm. The texture of SFZ in the pure Ti was affected by shear stress from the shoulder of stir tool and the c-axes of the grains in this zone were nearly parallel to the processing direction. While crystallographic texture in the normal stir zone (SZ) were nearly perpendicular to the processing direction. The maximum depth of SFZ in the sample with 180 rpm was 1.2 mm, which decreased with the increased rotation speed until it disappeared. The grains in the SZ of specimen following FSP at a slow rotation speed were fine and homogeneous. The microhardness increased from 150.2 HV to 191.6 HV after FSP at 180 rpm. The microhardness trends were related to grain sizes, work hardening and texture evolution. The slow rotation speed processed alloy boosted the yield strength by 71.7% after the FSP. Highlights • Shoulder friction zone of pure Ti formed during FSP with a slow rotation speed. • Texture was not uniform in the thickness direction of FSPed pure Ti processed with a slow rotation speed. • Grain size decreased and microstructure homogeneity in thickness increased in pure Ti by FSP with a slow rotation speed. • Mechanical properties of pure Ti were developed after FSP with a slow rotation speed. [ABSTRACT FROM AUTHOR]

T6 aging treatment was performed at 423 K and 473 K for AZT802 wrought magnesium alloy. To understand the effects of temperature on the aging behavior and mechanical properties, microstructure and uniaxial tensile performance at room temperature were studied. Aging temperature obviously affected the rate of precipitation. Temperature sensibilities of continuous precipitates and discontinuous precipitates were different and continuous precipitates were far more sensitive phases. With increasing aging temperature, continuous precipitates grew coarsely. Meanwhile, densities of continuous precipitates and part of discontinuous precipitates decreased rapidly. Mechanical properties and fracture analysis indicated that compact second phases reinforced matrix effectively. Cracks extended mainly through zones of discontinuous precipitates in the sample which was aged at 423 K. But when the aging temperature raised to 473 K, the sample tended to fracture mainly along zones of continuous precipitates and coarsely discontinuous precipitates. [ABSTRACT FROM AUTHOR]

The microstructure and mechanical properties of AZ80 wrought magnesium alloys with varying Sn contents (0, 1, 2 and 4 wt.%) have been studied by thermodynamic and precipitation kinetics calculation and examined using scanning electron microscopy (SEM), transmission electron microscopy (TEM), hardness test and uniaxial tensile test at room temperature in this paper. The results of thermodynamic and precipitation kinetics calculation showed that the precipitation sequences were determined by the content of Sn element. It was found that in the aging treatment of this work, Mg 17 Al 12 phase precipitated sooner than Mg 2 Sn phase in the alloys with less than 1.72 wt.% Sn and there was a contrary precipitation sequence of these two phases in the alloys with more than 1.72 wt.% Sn. Experimental results were in agreement with those of calculation. According to SEM and TEM observation, Sn promoted precipitation of Mg 17 Al 12 on aging temperature, however the preferential Mg 2 Sn phase suppressed discontinuous Mg 17 Al 12 precipitates by hindering the growth of these in their growth direction. AZ80 with 1–2 wt.% Sn as-aged alloys exhibited outstanding mechanical property that UTS, YS and EL were ∼420 MPa, ∼290 MPa and ∼5%, respectively. [ABSTRACT FROM AUTHOR]

Friction stir processed Ti‐6Al‐4V alloys are successfully prepared under low rotation speed (≤200 rpm) and low traverse speed (≤50 mm min−1). The microstructure of the stir zone is homogeneous in thickness. Effects of process parameters on microstructure and texture evolution of α‐Ti in the stir zone during friction stir processing are clarified. It is found that traverse speed had a significant impact on microstructure in the stir zone. The equiaxed nano‐crystalline α‐Ti grains without texture formed via friction stir processing below β transus. The high temperature range and severe deformation range are overlapped when the samples are processed with low traverse speed. Dynamic recrystallization happened repeatedly and fast cooling inhibited grain growth when the stir tool moved away the stir zone. Ti‐6Al‐4V alloy shows shear texture after friction stir processing below β transus with higher traverse speed. β → α transformation occurred and lamellar α colonies formed during cooling stage above β transus when the rotation and traverse speed are increased. The microstructure morphology and texture strength of Ti‐6Al‐4V plates could be regulated by combining of heating and cooling stages during friction stir processing. [ABSTRACT FROM AUTHOR]

A small amount of Ca and Sn is added into AZ31 alloy separately to modify its deformation behavior and optimized rolling texture. Results show that addition of Sn increases the activation of twinning in AZ31. Some unusual double twins, inducing {101¯2}‐{101¯2} and {101¯3}‐{101¯2} double twins, are activated in AZ31–0.5Sn alloy. Refined grains with similar orientation as their parents are produced by continuous static recrystallization, which limits texture modification in AZT310. Ca gives rise to a remarkable grain refinement during hot rolling. Recrystallized grains in AZX310 exhibit a weaker double peak texture with a wide orientation spread. It is found that Al2Ca particles simulate recrystallized nucleation and some of these refined grains exhibit non‐basal orientations. Primary compression twins are favorable nucleation sites for recrystallization and they are more effective in texture modification compared to other double twins. [ABSTRACT FROM AUTHOR]

Effect of Al addition on microstructure and texture evolution during hot rolling of Mg alloys was investigated using Mg-(3, 6 and 9 wt%)Al-Zn series alloys. The results showed deformation behaviors, including twinning, dynamic recrystallization and activation of slip system, were affected by the increase of Al content. Compared with AZ31 Mg alloys, the rolled AZ91 sample exhibited strong basal texture and intensity of basal texture decreased by increasing rolling strain. Unlike double twins and contraction twins which were commonly observed in the hot rolling of AZ31 Mg alloys, twinning behavior was strongly suppressed by the addition of Al content. It was observed some grain-like extension twins nucleated inside unrecrystallized grains with ultrafine size in AZ91. The size of dynamic recrystallized grains in AZ91 was ultrafine compared to that of AZ31 due to pinning effect produced by small Mg 17 Al 12 particles. These recrystallized grains were distributed along grain boundaries and would continuously coordinate further deformation strain after their nucleation. The increase of the area fraction of recrystallized grains resulted in a texture weakness during large strain rolling in AZ91. Geometrically necessary dislocation information was analyzed for the rolled samples. It showed prismatic slip took an advantage in AZ31 rather than AZ91 during hot rolling, which may be a reason for the weaker basal texture of unrecrystallized grains in AZ31. [ABSTRACT FROM AUTHOR]

Commercial AZ31 Mg alloys sheet was hot rolled by 50% thickness reduction in a single pass. The rolling process was manually interrupted before the entire sheet was rolled, and an intermediate-rolled sample was obtained. The microstructure, texture and mechanical responses on both surface and mid-layer of the intermediated-rolled sample were investigated. Our results show that the thickness gradients of microstructure and texture of as-rolled sheet were mainly caused by heterogeneously severe deformation when the surfaces of the sheet were bitten by the rollers. Both discontinuous and shear bands related dynamic recrystallization were observed. The recrystallized grains inside shear bands first nucleated in twins. The refined grains exhibited a strong basal texture with random distribution of 〈 11 2 ¯ 0 〉 direction. Discontinuous release of deformation strain during hot rolling led to strain flow localization, which resulted in formation of shear bands. Shear bands helped to coordinate the strain distribution between two nearby regions to prevent cracking in large strain rolling. [ABSTRACT FROM AUTHOR]

The effect of pre-twinning process on dynamic recrystallization, texture and mechanical properties of Mg alloys sheets was investigated by rolling pre-compressed AZ31 Mg sheets at 350 °C. Two types of pre-compressed sheets with different initial texture component were rolled by 60% thickness reduction in a single pass for observation. Microstructure, texture and mechanical properties evolution during large strain rolling were carefully investigated. The results show that dynamic recrystallization is greatly promoted by pre-compression process. Twin structures are more effective in enhancing dynamic recrystallization than pre-deformation strain stored during compression. Besides slip, detwinning is regarded as an important deformation mode when pre-twinning samples are rolled along their compression directions. Low temperature annealing of pre-twinning samples prior to rolling hinders detwinning process, resulting in an increase of yield stress. The basal texture and plane-anisotropy are greatly weakened in the sample rolled perpendicular to the pre-compression direction. The mechanical properties of rolled sheets were promoted by pre-twinning process. [ABSTRACT FROM AUTHOR]

Laser surface remelting (LSR) was performed on a Mg-6.2Y (at.%) magnesium alloy to enhance mechanical properties of its surface. The results show that both grains and secondary phase were greatly refined by LSR. The ε phase (Mg 24+ x Y 5) was redistributed from α -Mg grain boundaries to interior of the grains. The Y content of ε phase decreased from 14.3 to 9.3 at.% due to the LSR. Some metastable Y-rich nano particles were formed on the ε phase due to the rapid solidification. Mechanical properties of treated surface were significantly improved due to grain refinement and phase redistribution. Compressive strength of the treated region was increased to 606 MPa and exhibited a moderated ductility compared to the initial material. The increase of ductility by LSR is related to the uniformed redistribution of ε phase, which led to a homogeneous distribution of strain. [ABSTRACT FROM AUTHOR]

The effects of Nd addition on the microstructure and mechanical properties of Mg–6Zn–1Mn–4Sn alloy have been investigated. The results show that α-Mg, α-Mn, Mg 7 Zn 3 , Mg 2 Sn and MgSnNd phases are found in the as-cast Nd-containing alloys. The MgSnNd phase is a high temperature phase which can enhance the age hardening response of the heat-treated alloys. The ZMT614–1.5Nd alloy under the extruded and aged states exhibits higher strength. This is mainly attributed to the fine grains after extruding and high number density of rod-shaped β 1 ′ precipitates in the α-Mg matrix after aging, respectively. [ABSTRACT FROM AUTHOR]

Hot rolling with three different rolling thickness reductions (20%, 40% and 70%) was carried out by single rolling pass on AZ31 Mg alloy sheets at three different rolling speeds varying between 3.5 and 12.1 m/min. The evolutions of the microstructure and mechanical properties of the hot rolled samples were critically examined. The results showed that twinning was the dominant deformation behavior during hot rolling at small rolling reduction and secondary twinning was the main way of twinning in this rolling condition. At high rolling speed, dynamic recrystallization can be activated and further enhanced by increasing thickness reduction. As the microstructure was refined, both strength and ductility of the samples were improved by dynamic recrystallization. While no obvious dynamic recrystallization was investigated during hot rolling at low rolling speed, twinning was further enhanced by increasing thickness reduction at this speed, resulting in an increase in yield strength and a remarkable reduction in ductility. [ABSTRACT FROM AUTHOR]

Abstract: The influence of the rolling speed on microstructure and mechanical properties of as-rolled AZ31 Mg alloys sheet was critically examined. Samples were hot rolled by nearly 55% thickness reduction in a single rolling pass at rolling speeds varying between 3.5 and 12.1m/min. The results showed that twinning dominated the deformation at lower rolling speed and dynamic recrystallization was constricted in shear bands. While, at high rolling speed, dynamic recrystallization behavior was largely extended and microstructure became homogeneous. The yield behavior of as-rolled sheets was affected by the recrystallized grains formed during rolling. The tensile ductility was gradually improved as rolling speed increased, due to the enhancement of dynamic recrystallization. The dynamic recrystallization is an effective way to consume the deformation energy, which may suppress edge crack initiation. [Copyright &y& Elsevier]

AA2099 Al-Cu-Li alloys were rolled by both asymmetrical and conventional rolling to a total thickness reduction of 80% at room temperature. Microstructure and texture evolution through thickness of rolling sheets were comprehensively investigated. Results show that large shear stress in ASR sample gave rise to a distortion of grain structure and a remarkable work hardening at region close to fast rolled surface. Shear banding behavior was largely promoted by ASR and various types of shear bands with higher density were observed. The shear bands triggered a kink of grain structure during rolling process. The kink behavior was related to the tilt angle and width of shear bands. The shear bands exhibited large tilt angle and width gave rise to a more significant kink of the grain structure nearby. Recrystallization during subsequent annealing was also promoted by ASR. Shear bands became favorable nucleation sites for rolled material. Growth advantage of some nuclei inside shear bands had a stronger influence on the recrystallized texture in AA2099 rolled sheets. • Asymmetrical rolling brought inhomogeneous microstructure and texture through thickness. • Grain structure was kinked into several parts due to formation of shear band. • Kink behavior is depended on the direction and the width of shear bands. • Shear banding nucleation triggers uncommon recrystallized texture during annealing. [ABSTRACT FROM AUTHOR]

Microstructure evolution of severely cold rolled dual-phase Mg–Li alloy during annealing at various temperatures was systemically investigated. The results showed that severely deformed α-Mg phase can be significantly refined by annealing process. α-Mg phases were first stratified into various layers by phase transformation from α-Mg phase into β-Li phase. Low angle grain boundary was more easily inducing phase transformation compared to high angle one during annealing. α layers continuously broken into chains of α grains at high annealing temperature, which is controlled by the motion of triple junction at the intersection of phase and grain boundary. Grain boundaries exhibited a high interface tension compared to phase boundary, which drove the globularization of α-Mg grains. Mechanical properties and strain hardening behavior were influenced by phase refinement. Coordination of grain refinement and phase refinement promoted the ductility of dual-phase Mg–Li alloy without a remarkable decrease in strength. [ABSTRACT FROM AUTHOR]