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Dual-phase Mg-Li alloys sheets were rolled at four different temperatures ranging from liquid nitrogen to 300 °C to explore effect of rolling temperature on texture and mechanical properties of the material. Crystal plasticity simulation was utilized to illustrate the influence of slip activity on rolling texture development. The results show that the rolling texture is largely depended on deformation temperature. Unlike commercial Mg alloys, the critical resolved shear stress of basal slip in α-Mg phase of Mg-Li alloy decreased more significantly by increasing temperature compared to that of pyramidal slip. Enhancement of basal slip by increasing temperature triggered a decrease of split angle of basal poles for the double-peak texture. Prismatic slip largely enhanced by increasing temperature upon 200 °C, which induced a wider orientation spread along the transverse direction. For the β-Li phase, the promotion of {110}<111> slip system at elevated temperature triggered the enhancement of {211}<110> and {111}<211> texture components. The cryo-rolled sample exhibited the highest strength compared to the others due to a strong hardening behavior at this temperature. A two-stage hardening behavior was observed in these as-rolled dual-phase alloys. Strain transition at phase boundaries could be the reason for appearance of this two-stage hardening. [ABSTRACT FROM AUTHOR]

Strain-induced phase transformation in a dual-phase Mg–Li alloy after a severe deformation has been investigated. β-Li phase was transformed into α-Mg phase as a consequence of large strain cold rolling. The morphology and density of the strain-induced phase could be controlled by slip activation in the β-Li phase. A multi-direction rolling procedure was designed to enhance phase transformation behavior. High density strain-induced phase refined phase structure and greatly promoted the yield strength of the material without a sacrificing the ductility. Strain-induced phase transformation is a potential method for improving the mechanical properties in dual-phase alloys. Image, graphical abstract [ABSTRACT FROM AUTHOR]

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]

Friction stir processing (FSP) was successfully performed on ultra-light dual-phase LZ91 Mg Li alloy, which provided a chance to study the microstructure and texture evolution of this alloy during severe plastic deformation. The results showed that LZ91 Mg Li alloy could be processed successfully with 200–400 rpm, 25 mm/min, and water cooling during FSP. No defects were observed on the surface and in the cross-section. The microstructure was strongly influenced by the material flow modes during FSP. Two greatly phase refinement regions were found in the stir zone where the α-Mg and β-Li phases were refined to submicron scale and homogeneously mixed. Maelstrom currents flow between two threads on the pin triggered this phase fragment. The high rotation rate of FSP leads to a remarkable recrystallization and grain growth due to the high heat input. The severe plastic deformation caused a phase transformation inside the refined α-Mg phase. The new phases enriched Li element exhibited a coherent relationship with the matrix. It shows that FSP promoted the short-term diffusion in refined α-Mg. • Two phases in dual-phase Mg Li alloy were refined to submicron scale and distributed evenly after FSP. • Materials flow modes strongly influenced the grain refinement and phase distribution in FSPed Mg Li alloy. • A phase transformation inside refined α-Mg phase was discovered and analyzed. [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]

Twinning was regarded as an effective way to modify the precipitation in Mg alloys. Two procedures were designed to illustrate twinning-aging consequence on Mg 17 Al 12 phase evolution. The effect of multiple steps of twinning-precipitation on the morphology and density of the continuous precipitates inside the twins and the matrix were comprehensively analyzed through phase-orientation related observation. The results show the shape of precipitates in twins was similar to that in the matrix as the CPs mostly lay on the basal planes with an asymmetric-lozenges shape. The CPs were remarkably refined and its density became much higher inside twins. Moreover, the aspect ratio of the CP plates in twins was around 45% of that in the matrix, which means the CPs inside twins became more globular. The precipitation behavior of Mg 17 Al 12 phase inside double extension twins was different from the primary twin or the matrix. The Mg 17 Al 12 phases lay on both basal and prismatic planes can be observed in double twins of two-step precipitation. The growth behavior of pre-precipitates in twins is different from those in the matrix. The growth rate along its thickness became higher than that in the matrix, which is probably related to dislocation-assisted diffusion at the basal plane. • Morphology of CPs precipitated in the matrix, primary and double twins is different • Ratio of length and thickness of CPs in twins significantly decreased • CPs lay on basal and prismatic planes are prepared in one twin structure • Dimension of CPs precisely characterized by phase-orientation related observation [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]

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]

Microstructure and texture evolution of Mg-8.8 wt%Li-0.8 wt%Zn dual-phase alloy during cold rolling to 70% thickness reduction were investigated. The results showed that both α-fiber and γ-fiber of β-Li phase were enhanced during the cold rolling procedure and {001}<110> was the dominant texture component. A double-peak texture with a large tilt angle of 28° was observed in α-Mg phase. Each peak of this texture component exhibited a wider orientation spread towards the transverse direction. This spread is related to the strong activation of pyramidal II slip. Basal slip was still the dominant slip mode and the activities of pyramidal I and pyramidal II slip were also largely enhanced. Schmid factor analysis and viscoplasitc self-consistent simulation jointly suggests that the development of the rolling texture in α-Mg phase can be ascribed to the competition between basal slip and pyramidal slip. • Second order pyramidal slip was promoted in the dual-phase structure Mg–Li alloy. • Pyramidal II slip has a stronger impact on texture compared to pyramidal I slip. • Two stable rolling texture components were found in the α-phase. • Competition of basal and pyramidal slip has a strong impact on texture development. [ABSTRACT FROM AUTHOR]