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In this work, different transformed β matrix was obtained in Ti–5Al–7.5 V alloy. The alloy with equiaxed αp phase and transformed β matrix containing α′ martensite and β phase exhibits good combination of strength and plasticity, as well as a high work hardening rate. A concurrent operation of stress-induced α″ martensitic transformation, deformation twinning and dislocation slips was observed governing the deformation process of this alloy. The alloy with equiaxed αp phase and transformed β matrix containing secondary αs plates and retained β phase shows a high strength and plasticity but low work hardening rate, which is caused by dislocation slips. Highlights The quenched Ti–5Al–7.5 V alloy exhibits a high work hardening rate, approximately 5500 MPa. The dependence of work hardening rate of Ti–5Al–7.5 V alloy on transformed β matrix is revealed. Concurrent operations of stress-induced α″ martensitic transformation, deformation twinning and dislocation slips govern deformation of the studied alloy. [ABSTRACT FROM AUTHOR]

We introduced a strategic "Kinetic Diffusion Multiple" (KDM) that undergoes interdiffusion annealing followed by realistic thermal treatment. The blended spectra of phases and microstructures subjected to treatment in deeply grooved composition gradients enables the microstructure and micromechanical properties of structural materials to be surveyed by high-spatially resolved micro-analysis along the composition arrays. The KDM was demonstrated as a robust high-throughput methodology that enables rapid screening of the composition-microstructure-micromechanical/properties relationships for different metallic materials. It has also proven great success at elucidating the lasting effects of alloying elements and diffusion flux on microstructure, micromechanical properties, phase transformation, and their interrelationships as a whole. [ABSTRACT FROM AUTHOR]

• High-temperature "Inverse" Hall-Petch behavior was found in TA15 alloy. • Grain boundary-mediated deformation is the main mechanism of high temperature deformation. • By designing the grain size of specimen and distribution of the second phase, it is expected to fully exploit the high-temperature mechanical properties of the material. The Hall-Petch relationship is important for material design at room temperature. However, it is not well studied at high temperatures. In this work, the influence of different microstructures on the high-temperature mechanical behavior and corresponding softening mechanisms of high-temperature titanium alloy TA15 (Ti-6.5Al-2Zr-1Mo-1 V, wt.%) were studied. Specimens with duplex, Widmanstätten, and coarse Widmanstätten microstructures were obtained through powder metallurgy. High-temperature tensile tests were carried out between 500 and 650°C. It was found that the fracture mode of the Widmanstätten microstructure was transgranular at 500 °C and 550 °C, but intergranular at 600 °C and 650 °C. EBSD analysis revealed that the high-temperature deformation was facilitated by several mechanisms including GB softening, GB migration, grains rotation, and activation of multiple slip systems. High temperature nanoindentation indicated sofenting of individual grains with increasing temperature. In-situ tensile testing under SEM revealed deformation was primarily in grain interior at room temperature, and GBs played a significant role at 650℃. The GB behavior at high temperatures is believed responsible for the inverse Hall-Petch relationship. These findings provide a new perspective for improving the high-temperature mechanical properties and microstructure control of titanium and its alloys. [Display omitted] [ABSTRACT FROM AUTHOR]

Micropillar compression technique was employed to study the microscale deformation mechanisms of basal slip, twinning and non-basal slips at selected grains in a Mg-2 wt.% Y alloy. The results suggest a critical resolved shear stress (τCRSS) for basal slip 12.5 ± 1.7 MPa, and for twin nucleation and twin growth 38.5 ± 1.2 MPa and 33.8 ± 0.7 MPa, respectively. The higher values compared to those in pure Mg suggests a more balanced deformation in Mg alloy with Y addition. The activation of dislocations in the twinned orientation is highlighted, which leads to strong work hardening in twinned favorable orientation [ 10 1 ‾ 0 ]. In addition, at prismatic-slip favorable orientation [ 11 2 ‾ 0 ] , a twinning-to-prismatic slip transition was observed when elevating temperature from 25 °C to 100 °C and 250 °C. Specially at 250 °C, twinning was completely prohibited, and pure prismatic slip was triggered. The measured τ CRSS for prismatic slip at 250 °C was 39.7 ± 0.3 MPa, much higher than that for pure Mg at the same temperature. Finally, at pyramidal-slip favorable orientation [ 0001 ] , an abnormal strengthening was observed at 100 °C and 250 °C due to activation of pyramidal slips. Decompositions of dislocations and Y segregation at stacking faults are the main mechanisms leading to the high-temperature strengthening in Mg–Y alloy. [ABSTRACT FROM AUTHOR]

The microscopic deformation behavior is always been of significant interest in revealing the mechanism of the dwell fatigue effect. This study systematically characterized the deformation system activation in Ti–6Al–3Nb–2Zr–1Mo (Ti6321) alloy using in situ tensile and quasi-in situ dwell fatigue tests. The critical resolved shear stresses of the basal and prismatic slip systems in the Ti6321alloy were first calculated using the slip trace analysis method. The study demonstrated that, under dwell fatigue, basal and prismatic slips consist of major microscopic deformation modes. Most of the slip deformation occurred rapidly during the early stage of dwell fatigue and was independent of the dwell loading. The basal slip was found to be the predominant slip mode regardless of the dwell conditions. The results suggested that the elastic anisotropy of the hexagonal-closed-packed (HCP) structure could lead to heterogeneous microscopic stress, thus activating more basal slip activities. Such activities were found to participate in the crack initiation through two unique cracking modes: basal plane crack and (0001) twist boundary crack. [Display omitted] • The critical resolved shear stress was quantitatively evaluated through in situ tensile tests. • Dwell fatigue deformation modes were revealed by the crystallographic characteristics. • Basal slip deformation was proved to be the predominant slip mode and highly participated in the crack initiation. [ABSTRACT FROM AUTHOR]