Microstructural Deformation Mechanisms Research Articles

Hot compression behavior and recrystallization mechanism of 1.5 wt% Ti3AlC2 ceramic-enhanced Mo alloys with two-dimensional layers

Improving the high temperature strength of Mo alloys is a key problem to expand the application range of Mo alloys. In this study, the Mo-1.5 wt%Ti3AlC2 alloy was designed by introducing new two-dimensional (2D)-layered ceramic particles Ti3AlC2 into Mo. The peak flow stress of the Mo-1.5 wt%Ti3AlC2 alloy reaches 308 MPa at 1200 °C. The diffusion activation energy Q of the Mo-1.5 wt%Ti3AlC2 alloy is as high as 533.38 kJ/mol, which is higher than that of pure Mo (480 kJ/mol). Sintering in the reducing atmosphere of hydrogen at high temperature, the Ti3AlC2 consumes a large amount of energy to form AlTi3 and Ti5O9, which leads to an increase in the diffusion activation energy. We have established the constitutive equation of the Mo-1.5 wt%Ti3AlC2 alloy, and studied the microstructure evolution and deformation mechanism under hot compression. The results show that the stress index of n1 > 3 indicates that the plastic deformation mechanism was a dislocation mechanism. With the addition of Ti3AlC2, a large number of dislocations were produced in the alloy at the early stage of hot deformation. With increasing temperature, the dislocation entanglement gradually cancels out, resulting in the decrease of dislocation density. With the increase of temperature and deformation rate, the dynamic recrystallization (DRX) mechanism of the Mo-1.5 wt%Ti3AlC2 alloy was mainly continuous dynamic recrystallization (CDRX) at 1200 °C/0.01 s−1 and discontinuous dynamic recrystallization (DDRX) at 1600 °C/10 s−1. This work provides a new research direction for designing high performance Mo alloys.

In-situ investigate on the microstructure evolution, deformation and fracture mechanism of Mg-Gd-Zn-Mn alloy with varies of LPSO volume fraction

The induction of long-period stacking ordered (LPSO) phase through heat treatment was an effective method to strengthen magnesium alloys. In this study, the volume fraction of lamellar LPSO in the Mg-4Gd-1Zn-0.5Mn alloy was controlled by optimizing the heat treatment process. The research findings showed that with increasing heat treatment time, the volume fraction of LPSO initially increased then decreased until disappearing. The alloy treated at 500 °C for 2 h exhibited the highest volume fraction of lamellar LPSO, increasing from 1.64% to 13.68%. Further in-situ tensile tests were conducted on two types of alloys contain higher LPSO fraction (HL) and lower LPSO fraction (LL) at ambient temperature. The increased critical shear stress (CRSS) and obstacle effects on dislocations caused by LPSO effectively enhanced the strength of the alloy. The dominant deformation mechanisms of both HL and LL alloys are basal slip and twinning during tensile deformation. However, the HL alloy activated more non-basal slip significantly, which was ascribed to the activation of non-basal slip by LPSO kinking during deformation. Additionally, the bending and kinking of LPSO effectively restricted crack initiation and propagation, thereby enhancing the plasticity. The HL alloy exhibited fewer twin boundaries after deformation, which was attributed to the hindrance of twinning extension by LPSO.

Study on microstructure evolution, mechanical properties and deformation mechanism of Ti-6Al-4V alloy by hydraulic tension on-line warm rolling

In this research, Ti-6Al-4 V alloy thin strip with ultra-high tensile strength and good ductility combination was successfully prepared by a new high-efficiency short-flow on-line warm rolling processing method. To explore the intricate relationships between microstructure evolution, mechanical characteristics, and the deformation mechanism during on-line warm rolling of the Ti-6Al-4 V alloy, various analytical methods were employed, including OM, SEM, XRD, EPMA, EBSD, and TEM. When the rolling reduction escalated from a Warm Rolling (WR) rate of 70–90%, there was a concurrent increase in both the alloy's strength and ductility. In numerical terms, the ultimate tensile strength, yield strength, and total elongation rose from 1241 MPa, 1117 MPa, and 5.3% respectively at WR-70%, to 1366 MPa, 1214 MPa, and 8.2% at WR-90%. At WR-90%, the high strength of the resulting Ti-6Al-4 V alloy thin strip is ensured through a distinct combination of material adaptations. These include grain refinement, high-density dislocation accumulation, and the presence of both partial fine recrystallization and ultrafine grains. The initiation of the pronounced basal slip system {0001}< 11–20 > coupled with the pyramidal system {11−22}< 11–2–3 > plays a pivotal role in retaining ductility even under conditions of elevated strength. The amalgamation of grain refinement, dense dislocation accumulation, and the juxtaposition of partial fine recrystallization with ultrafine grains, in tandem with the prevailing basal slip system {0001}< 11–20 > and the active pyramidal system {11−22}< 11–2–3 > , ensures the preservation of commendable ductility while simultaneously achieving high strength. This successful creation of the high-performance Ti-6Al-4 V alloy thin strip provides crucial parameters and theoretical guidance for the industrial application of the hydraulic tension on-line warm rolling method for titanium alloys and other similarly difficult-to-deform metals.

Shock-compression microstructure transformation of the additive manufactured FeCoNiAlTi high-entropy alloy

Investigation into the microstructural deformation mechanisms of a high-entropy alloy (Fe28.0Co29.5Ni27.5Al8.5Ti6.5 (at%)) prepared by laser additive manufacturing and aging treatment, with a three-phase nanocomposite structure, is carried out via shock compression experiments using plate impact. Microstructural characteristics and compositions are inspected using X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The microstructure of the high-entropy alloy is comprised of high-density dislocation structures, high-volume-fraction L12 nano-precipitates, a small amount of L21 nano-precipitates, and face-centered cubic (FCC) matrix phases. The lattice arrangement of the FCC matrix phase is disordered, with strong segregation of Fe and Co atoms, while Ni, Al, and Ti atoms are predominantly present in the ordered L12 and L21 nano-precipitates. The FCC matrix or the FCC matrix with high-density stacking faults are bounded by a 9R-phase between two phase boundaries. The mechanisms of microstructural transformation of the high-entropy alloy are discussed in detail.

The Influence of Overburden Stress and Molding Water Content on the Microstructure of Remolded Loess

This study aims to reveal the mechanisms of the microstructural evolution of remolded loess under different molding water contents and overburden stresses. Utilizing L6 loess from Yan’an, remolded soil specimens were fabricated under various pressures and moisture contents, followed by conducting one-dimensional consolidation tests. The macroscopic porosity, pore size distribution curves (PSD), and microstructure of these remolded loess samples were examined. Experimental findings indicate that an increase in molding water content leads to an augmentation in macroscopic pore volume and elongated pore shapes, concurrently exerting substantial influence on the primary pore size and pore volume of both macropores (&gt;0.4 μm) and minipores (0.4–4 μm), with minimal impact on micropores (&lt;0.4 μm). The escalation of overburden stress solely contributes to the reduction in pore size and pore volume of macropores. Variations in the Menger fractal dimension occur only beyond the optimal water content, while overburden stress exhibits a minimal effect on the Menger fractal dimension. Furthermore, remolded loess exhibited a certain yield stress, and when the overburden stress was lower than the yield stress, there was almost no change in various types of pores. Finally, a microstructural evolution model of remolded loess under different molding water contents and overburden stresses was proposed. These findings are expected to provide new insights into the microstructural evolution and deformation mechanisms of loess in high embankment construction sites.

Microstructure evolution and deformation mechanisms during compression of a harmonic–structured Ti–24Nb–4Zr–8Sn alloy

Processing heterogeneous microstructures, especially the so-called harmonic structures consisting of soft core and hard shell regions, is an efficient way to achieve a strength-ductility trade-off in classical metallurgy. In this study, two harmonic samples with the same composition of Ti–24Nb–4Zr–8Sn but different microstructures were processed to exhibit different grain size heterogeneities between the core and the shell. Both samples were consolidated from a ball-milled powder using Spark Plasma Sintering (SPS) but applying two different sintering times, 1 and 60 min. The grain size heterogeneities were higher for the longer SPS sintering time due to the enhanced grain dimension in the core for 60 min consolidation time. The mechanical behavior of the two materials was studied via a monotonic quasi-static compression test. For both harmonic-structured Ti–24Nb–4Zr–8Sn alloys, a high compressive proof stress of about 1 GPa was detected. The strain-hardening rate was higher for the longer SPS time due to the higher grain size differences between the core and shell. A high dislocation density was detected in both materials after compression deformation (several tens of 1014 m−2). The dislocations tend to form cells and LAGBs during compression. The dislocation pile-ups at the core-shell interfaces caused a back stress of about 640 MPa after compression at 2–5% strains. The contributions of the different features of the microstructure (grain size, α phase precipitates, and oxygen concentration) to the proof stress were determined.

A comparison of thermo-mechanically-treated and electron-beam-welded strong, ductile medium-entropy alloy: Microstructural evolution and deformation mechanisms

The microstructure, room-temperature deformation mechanisms, and weldability of the medium-entropy alloy (MEA) NiCoVAl0.2 have been investigated. Defect-free welded joints have been produced with good mechanical properties, indicating excellent weldability. The microstructure consists of f.c.c. grains containing many b.c.c. Ni2VAl (Ni26.1Co33.5V27.8Al12.6) and few σ-type precipitates (Ni15.5Co21.3V62.7Al0.5). Decreasing the aging temperature from 1100 °C to 900 °C, produced a higher area fraction of Ni2VAl precipitates (8 → 25%), much smaller L21 precipitates (7.2 → 1.4 μm), finer grains (17.1 → 2.4 μm), and presence of σ-type precipitate, resulting in simultaneous improvements in both the strength and ductility for both the thermo-mechanically treated (TMT) and electron beam welded (EBWed) MEA. The TMT MEA shows an excellent combination of strength (YS∼993 MPa, UTS∼1478 MPa) and ductility (30.3%), while the EBWed MEA shows slightly lower strength (YS∼822 MPa, UTS∼1194 MPa) and significantly reduced ductility (12.3%), i.e. a YS, UTS, and ductility of 83%, 81%, and 41%, respectively, of those of the TMT MEA. With increasing strain, both low-angle grain boundaries and geometrically-necessary dislocation (GND) densities increased. The TMT MEA has a higher GND density (1.6 × 1015 m−2) than the 9.1 × 1014 m−2 of EBWed MEA after strained to fracture. For both the TMT and EBWed MEA aged at 900 °C, the deformation was accommodated by dislocation slip, dislocation looping around precipitates, and nano-twinning. However, for both the TMT and EBWed MEA aged at 1100 °C, more abundant deformation twinning and an fcc→hcp shear transformation appeared, which may originate from a lower stacking fault energy due to differences in the f.c.c. matrix composition.

Multiaxial non-proportional fatigue behaviour and microstructural deformation mechanisms of 9%Cr steel at elevated temperature

High-temperature components utilised in practical service are often subjected to multiaxial non-proportional loading due to their complex geometry. In the present study, a set of strain-controlled fatigue tests were conducted on P92 steel at 600 °C, including uniaxial, multiaxial proportional, and multiaxial non-proportional loading conditions. Results reveal that the axial and shear stresses exhibit varied responses to the different non-proportionalities, with proportional loading resulting in the shortest fatigue life when the strain ratio is small. The non-proportional loading induces accelerated cyclic softening at axial direction while the shear stress is enhanced. Electron backscatter diffraction (EBSD) and transmission electron microscope (TEM) analysis indicate that the increased role of shear stress promotes the dislocation motion from the planar slip to cross-slip under non-proportional loading, which in turn facilitates the microstructure evolution. It is also important to note that the evident development of microstructure and the combined effect of more crack initiations and more secondary cracks contribute to the lowest fatigue life under proportional loading.

Suppression of mechanical instability in bioabsorbable ultrafine-grained Zn through in-situ stabilization by ZnO nanodispersoids

The issue of intrinsic microstructural and mechanical instability of Zn-based metals limits their expansion in potential applications of bioresorbable stents and orthopedic fixators. A new concept of stabilization of Zn microstructure by a small fraction of nontoxic nanometric ZnO dispersoids is proposed for the first time and demonstrated on the particular bioabsorbable model material. The effect of the ZnO dispersoids on post-processing microstructural stability, deformation and strengthening mechanisms, corrosion, and in-vitro biological behavior are pursued. The ZnO dispersoids arise in situ within deformed Zn structure during the consolidation of fine atomized Zn 99.99wt.% powder by hydro-extrusion. ZnO nanodispersoids (4.75 vol.%; ∼136 nm) form from passivating films present on Zn. They allow formation of ultrafine-grained Zn structure with an average grain size of ∼750 nm and its retention by Zener pinning action during annealing held at 100 °C. The model Zn + ZnO composite shows the superior mechanical properties than those reported for pure Zn materials. The utilized stabilization concept doesn't compromise corrosion and biological responses. Immersion of the Zn + ZnO in DMEM results in a corrosion rate, which complies with the desirable standard rate for biodegradable materials. Electrochemical tests suggest that the Zn + ZnO reaches a similar degradation rate after the first week of immersion and a more uniform corrosion behavior compared to the cast Zn reference. In-vitro cyto/genotoxicity assays performed using DMEM diluted extracts of the Zn + ZnO and cast Zn incubated with L929 cells yield in comparable and non-toxic responses. The presence of ZnO dispersoids induces a small but still significant bacteriostatic activity.

Experimental investigation and crystal plasticity simulation for the fatigue crack initiation of the equiaxed Ti-6Al-4V alloy in the very high cycle regime

This work investigated the fatigue crack initiation mechanism of the equiaxed Ti-6Al-4V alloy in the very high cycle fatigue (VCHF) regime. Ultrasonic fatigue experiments were carried out on Ti-6Al-4V specimens and a detailed analysis of the failure mechanism was conducted by means of scanning electron microscopy (SEM). The localized cyclic plastic response of the alloy was investigated using the crystal plasticity finite element (CPFE) method to further clarify the fatigue crack initiation process in the VHCF regime, and the CPFE models with varying transformed β(βt) phase volume fractions were presented to investigate the impact of βt phase on the VHCF behavior. The simulation results indicate that the proposed CPFE model can effectively captures the microstructural plastic deformation mechanisms, such as stress concentration near the phase boundaries and plastic accumulation. And the βt phase significantly affects the VHCF behavior of the alloy.

The behaviour and deformation mechanisms for 316L stainless steel deformed at cryogenic temperatures

The microstructural evolution and deformation mechanisms of 316L stainless steel (SS) have been investigated at 297, 173, 50 and 15 K by in situ neutron diffraction during tensile loading and correlative transmission electron microscopy (TEM). The yield strength and ultimate tensile strength of 316L stainless steel are significantly improved at cryogenic temperatures. In contrast to room temperature, deformation-induced martensitic transformation was observed at all cryogenic temperatures. The γ-austenite (FCC) content decreases and α′-martensite (BCC) increases with increasing strain, a fraction of this γ to α′ transformation is accompanied by the transient appearance of ε-martensite (HCP) as an intermediate phase. The maximum volume fraction of ε-martensite increases with decreasing deformation temperature and reaches 13% for deformation at 15 K. TEM results confirm that γ → ε → α′ and γ → α′ martensitic transformations occur during cryogenic deformation, while mechanical twins were observed only at 173 K. The evolution of lattice strain, phase volume fraction, stacking fault probability (SFP) and stacking fault energy (SFE) were quantified to investigate the correlation between deformation mechanisms and mechanical behaviour of 316L SS as a function of deformation temperature.

Effect of strain rate on the microstructure evolution and superplastic deformation behavior of cold-rolled medium Mn lightweight steel

This work investigates the high-temperature tensile behavior of a Medium Mn lightweight steel (MMLS) with a chemical composition of Fe-0.3C-7.0Mn-3.5Al. The MMLS was prepared by hot-rolling followed by cold-rolling to produce a complete martensite microstructure with a high density of dislocations. The tensile tests were conducted at 800 °C within the strain rate range of 5 × 10−4 s−1-2.5 × 10−2 s−1 to explore the effect of microstructural evolution and deformation mechanism by strain rates during the tensile deformation. The results showed that the deformation behavior and mechanism of the MMLS depend not only on the initial grain size and morphology but also on the microstructure evolution during deformation. The MMLS exhibits high strain rate superplasticity (HSRS) behavior, and the deformation mechanisms are dependent on the strain rate. At lower strain rate (5 × 10−4 s−1), dislocation slip/creep is more pronounced in the γ-phase, and grain boundary sliding (GBS) is inhibited during the early deformation period, contributing to the significant texture enhancement. At moderate rate (5 × 10−3 s−1), GBS dominates deformation, while at high strain rate (2.5 × 10−2 s−1), dislocation activity and dynamic recrystallization (DRX) play a significant role. The HSRS behavior of MMLS is related to the dynamic reverse phase transition from cold-rolled ferrite to austenitic/ferrite fine-grained dual-phase structure. This work provides a theoretical basis for the development of superplastic MMLS with improved HSRS behavior and controlled the microstructure/mechanical property of component parts.

Microstructure evolution and deformation mechanisms of a banded-grained 2A97 Al–Cu–Li alloy during superplastic deformation

The microstructure evolution and superplastic deformation mechanisms of a 2A97 Al–Cu–Li alloy (Al-3.4Cu-1.5Li-0.5Zn-0.4Mg-0.3Mn-0.15Zr) with initial banded grains were studied by using electron backscatter diffraction and focused ion beam techniques. The uniaxial superplastic tensile tests were carried out at a temperature of 430 °C and an initial strain rate of 2 × 10−3 s−1. The surface studies under a large true strain range (0–1.61) were achieved to investigate the superplastic deformation mechanisms. The results showed that the banded grains transformed into equiaxed grains due to dynamic recrystallization during deformation, accompanied by texture spreading, misorientation distribution randomization, and dislocation density reduction. The superplastic deformation process can be divided into two stages according to the microstructure characteristics and deformation mechanisms. In the primary deformation stage, the alloy was mainly composed of banded-grained structures, the intragranular dislocation slip (IDS) dominated the deformation and accounted for 54.1% contribution to the total deformation. When the true strain raised to 1.1, the deformation entered the second stage where the equiaxed grains became dominant, the grain boundary sliding became the main deformation mechanism and accounted for 54.4% contribution to the total deformation. A modified Ashby−Verrall model accompanied by IDS is suggested, which plays a crucial role in the superplastic deformation of the studied alloy.

The effects of Ti and Ta on the microstructure and high temperature deformation mechanisms of the CoNi-based superalloys

The effects of Ti and Ta on the microstructure and high temperature deformation mechanisms of the CoNi-based superalloys

Microstructural evolution and high-temperature deformation mechanism of 4Cr5MoSiV1Ti steel

Hot-working die steel usually withstands complex loading conditions and higher service temperatures, and its mechanical properties will inevitably deteriorate because of dynamic recovery, recrystallization, and plastic deformation of tempered martensite during service. A systematic study was carried out on a newly developed 4Cr5MoSiV1Ti hot working die steel to clarify the related microstructure evolution and deformation mechanism by stretching deformation at different temperatures ranging from room temperature to 640 °C. Results obtained show that the ultimate and yield tensile strength values at room temperature are about 1904 MPa and 1691 MPa, respectively. With increasing testing temperature, the strength decreases, the plasticity increases, and the fracture mode changes from brittle to ductile. All of these are closely related to a combined effect of tempered martensitic dynamic recovery, recrystallization, and secondary phase re-dissolution. Deformation mechanisms change from dislocation slip to rotation or sliding of ferrite with increasing stretching temperature.

Effect of extrusion temperature on microstructure, mechanical properties, and deformation mechanism of Mg-2.5Er-0.6Zr alloy

Different extrusion temperatures (350 °C, 380 °C, 410 °C) were used to forward extrude the cast Mg-2.5Er-0.6Zr (wt.%) alloy. The effects of extrusion temperature on the microstructure, mechanical properties, deformation texture and extrusion deformation mechanism of Mg-2.5Er-0.6Zr alloy were studied by OM, SEM, room temperature tensile test, EBSD and IGMA analysis. The results show that the cast alloy has coarse grains and exhibits random texture characteristics. After extrusion, the alloy underwent dynamic recrystallization (DRX), and the equiaxed grains were refined, forming a special rare earth texture, and the mechanical properties of the alloy were greatly improved. In the temperature range of 380 °C–410 °C, with the increase of extrusion temperature, the alloy grain coarsing, strength and plasticity gradually decrease, but it is still much higher than the cast alloy. Under the combined influence of fine grain strengthening, texture weakening and diversified plastic deformation modes, the comprehensive mechanical properties of extruded Mg-2.5Er-0.6Zr alloy are the best at 380 °C, and its ultimate tensile strength, tensile yield strength and elongation are 218.7 MPa, 184.2 MPa and 44.1%, respectively.

Reconfiguring dual-phase structure with equal micro-hardness to achieve double strength with slight ductility sacrifice

• After flash annealing, the hardness of ferrite and austenite is equal. • The steel obtains the doubling yield strength with slight elongation sacrifice. • Hall-Petch strengthening contributes 60% to yield strength, 40% by HDI hardening. • The high strain hardening rate originates from the multiple deformation mechanisms. • The multilevel SF networks and high-density L-C locks can improve strain hardening. The application of duplex stainless steel is severely restricted owing to its inherently low yield strength. A high yield strength of duplex stainless steel is required to address the lightweight issues and reduce the emission of polluting gases. Herein, excellent mechanical properties of duplex stainless steel were achieved using a flash annealing treatment to obtain austenite and ferrite phases with equal hardness, and the yield strength doubled without a substantial ductility sacrifice. The improvement in yield strength was caused by the grain boundary strengthening (a contribution of 60% to the yield strength) and hetero-deformation-induced strengthening (remaining 40% contribution to the yield strength) owing to the significant difference in the strain partitioning between the two phases. The high strain-hardening capability ensured ductility without a significant decrease; this correlated to the multiple microstructure deformation mechanisms. These mechanisms included the synergetic deformation of the ferrite with dislocation cell formation and austenite accompanied by the sequential appearance of dislocation accumulation, stacking faults, and deformation-induced nanoscale twins and martensite. Deformation-induced multilevel stacking fault networks and high-density Lomer-Cotterll locks further improved the strain hardening response by enhancing the hetero-deformation behavior of austenite and ferrite.

Analysis of microstructure evolution and deformation mechanism of nano-oxides Al2O3 dispersion strengthened copper alloy during compression at room temperature

The refinement of grains to the size of ∼ 600 nm is observed in a nano-scaled Al2O3 dispersion-strengthened (ODS) Cu alloy under compression distortion. The plastic deformation mechanism of the ODS Cu alloy is studied by the observation and analysis of the evolution of grain size, dislocation density and distribution, and texture orientation during compression process. The deformation process can be divided into four stages, i.e., leaner deformation stage, plastic-strengthening transition stage, relative steady state stage and softening stage under ∼ 90 % compression, according to the stress-strain curves. The grains are found split into refined sub-grains by the net-like entangled dislocations due to the pinning effect of nano-scaled Al2O3 particles. The dislocation density of ODS Cu is found increasing within 30 % compression, and then remaining to a plateau under ∼ 30 %−60 % compression, but then under ∼ 60 %−80 % and ∼ 80 %−90 % compression, the dislocation density increases firstly and then decreases. The crystal orientation is transformed from the Goss texture {110}< 001 > to the inhomogeneous Shear texture {001}< 110 > during the compression process, due to the rotation of grains. This study provides a further understanding of the strengthening mechanism and a guidance for the design of ODS Cu alloys, which is significant for the prospective future structural applications.

Microstructure evolution and deformation mechanism of Mg−Zn−Gd sheet during Erichsen cupping test

AbstractAn Erichsen cupping test of GZ31 sheet at room temperature with different reductions was carried out, and four samples with IEs (Erichsen index) of 2.0, 4.1, 7.1, and 7.3 mm were obtained. The deformation and fracture mechanisms of the cupping deformation process were studied by OM, SEM and EBSD. The results show that the IE of the GZ31 rolled sheet with the non-basal texture can reach 7.3 mm. Basal and pyramidal dislocation slips and {10 1-2} extension twinning are the main deformation modes during the Erichsen cupping test. The dislocation slip is hindered by the second phase particles and grain boundaries and entangles with each other to form voids, which eventually leads to the fracture of the material. The reason for the GZ31 sheet showing high IE is that the weak non-basal texture and rare earth elements are favorable for dislocation slip and extension twining to coordinate deformation.

Study on the dynamic deformation behavior and microstructure evolution of Ti-5Al-2.5Sn utilized Quasi-In-Situ method

In this paper, the microstructural evolution process and deformation mechanism of annealed Ti-5Al-2.5Sn alloy under a high strain rate of 2700 s−1 were investigated by quasi-in-situ method. The main deformation mechanism is found to be dislocation slip in the strain range from 0 to 0.05, and about 96% of the whole grain is deformed by dislocation slip, and prismatic slip dominates the plastic deformation. When the strain increased from 0.05 to 0.10, the original slip system continued to move, and 13% of the whole grain activates the new slip system. In the strain range from 0.10-0.20, the number of slip traces does not increase significantly, and the new slip system is difficult to be activated. In the whole deformation process, about 42% of whole the grain activates a variety of slip systems including prismatic slip and pyramidal <a> slip which activated at the same time. Results show that twin only appeared in a few grains in the whole observed region, indicating that twinning is not the dominant deformation mechanism of annealed Ti-5Al-2.5Sn alloy at a high strain rate.