STRAIN INDUCED STRUCTURAL TRANSITION OF INTERFACES AND TWINS IN A HOT－DEFORMED DUAL－PHASE TIAL ALLOY

The structure characteristics of a2/γinterfaces and the features of deformation twins in a quasi-isothermal forged Ti-45Al-10Nb alloy were studied by highresolution transmission electron microscopy. Three types of strain induced a2/γinterfaces and two types of strain induced twin boundaries were identified The most,important features are high density of ledges and the existence of I/3[111] Frank partial dislocation. Mechanisms for the formation these interfaces were proposed Two types of deformation twins were observed These deformation twins always start from the ledges it seems that ledges at interfaces are important features of interfacial structure for the mechanical behavior of alloys.

Microstructural Features During Strain Induced Ferrite Transformation in 08 and 20Mn Steels

The microstructure evolution during strain induced ferrite transformation was followed in thermal-simulation tests of clean 08 and 20Mn steels. The influences of carbon equivalence and initial austenite grain size on ferrite grain refinement and the volume fraction of ferrite during straining were inspected. The results revealed that the accelerating effect of ferrite transformation by strain was increased as the carbon equivalence decreased. However, finer ferrite grains were obtained at higher carbon content. At strain of similar to1.5 ferrite grains less than 3 mum and 2 mum can be obtained in 08 and 20Mn steels respectively. Whereas the ferrite grain refinement in 08 steel was due to both effects of strain induced transformation and ferrite dynamic recrystallization, that in 20Mn was mainly due to strain induced transformation. Heavy strain can produce fine ferrite grains in coarse austenite grained 08 steel, but it would lead to band microstructure in coarse austenite grained 20Mn.

STRAIN INDUCED STRUCTURE TRANSITION IN HOT DEFORMED γ+α DUALPHASE TITANIUM ALUMINIDE

ＳＴＲＡＩＮＩＮＤＵＣＥＤＳＴＲＵＣＴＵＲＥＴＲＡＮＳＩＴＩＯＮＩＮＨＯＴＤＥＦＯＲＭＥＤγ＋αＤＵＡＬＰＨＡＳＥＴＩＴＡＮＩＵＭＡＬＵＭＩＮＩＤＥ①ＣｈｅｎＧｕｏｌｉａｎｇａｎｄＷａｎｇＪｉｎｇｕｏＳｔａｔｅＫｅｙＬａｂｏｒａｔｏｒｙｆｏｒＡｄｖ...

EFFECT OF COPPER AND BORON CONTENT ON STRAIN-INDUCED Nb(C,N) PRECIPITATION IN ULCB STEELS AT HOT DEFORMATION TEMPERATURE

The stress relaxation curves of Ultra-Low Carbon Bainitic(ULCB) steels with different Cu and B contents were measured by using Gleeble-1500 dynamic thermal-mechanical simulator. The results show that Cu and B added can accelerate the strain-induced precipitation reaction, and the effect of Cu and B is even more obvious with Cu and B combined addition or Cu content increased. The TEM analysis of precipitate engendered at the temperature of 850℃ C indicate that Nb(C,N) precipitate nucleates dominantly on the dislocation line, and grows with holding time extended while the precipitate particle size increases from 5 nm to 17 nm.

Effects of pre-deformation on microstructure and tensile properties of Al-Zn-Mg-Cu alloy produced by modified strain induced melt activation

The effects of Al-8B grain refiner on microstructure and tensile properties of an Al-12Zn-3Mg-2.5Cu alloy produced by modified strain induced melt activation process were investigated. Pre-deformation of 60% was used by hot working at 300 ℃. After pre-deformation, the samples were heated to a temperature above the solidus and below the liquidus point and maintained in the isothermal conditions at three different temperatures（500, 550 and 590 ℃） for varying time（10, 20 and 40 min）. It was observed that strain induced melt activation has caused the globular morphology of α（Al） grains. Microstructural study was carried out on the alloy by using optical microscope and scanning electron microscope in both unrefined and B-refined conditions. The results showed that for the desired microstructures of the alloy during SIMA process, the optimum temperature and time are 550 ℃ and 10 min, respectively. After the T6 heat treatment, the average tensile strengths increased from 278 to 585 MPa and 252 to 560 MPa for samples refined with 3.75% Al-8B before and after SIMA process, respectively. The ultimate strength of SIMA specimens is lower than that of B-refined specimens.

Characteristics of anomalous Hall effect in spin-polarized two-dimensional electron gases in the presence of both intrinsic,extrinsic,and external electric-field induced spin-orbit couplings

The various competing contributions to the anomalous Hall effect in spin-polarized two-dimensional electron gases in the presence of both intrinsic, extrinsic and external electric-field induced spin-orbit coupling were investigated theoretically. Based on a unified semiclassical theoretical approach, it is shown that the total anomalous Hall conductivity can be expressed as the sum of three distinct contributions in the presence of these competing spin-orbit interactions, namely an intrinsic contribution determined by the Berry curvature in the momentum space, an extrinsic contribution determined by the modified Bloch band group velocity and an extrinsic contribution determined by spin-orbit-dependent impurity scattering. The characteristics of these competing contributions are discussed in detail in the paper.

Martensitic Transformation and Magnetic-Field-Induced Strain in Magnetic Shape Memory Alloy NiMnGa Melt-Spun Ribbon

A magnetic shape memory alloy with nonstoichiometric Ni50Mn27Ga23 was prepared by using melt-spinning technology. The martensitic transformation and the magnetic-field-induced strain (MFIS) of the polycrystalline melt-spun ribbon were investigated. The experimental results showed that the melt-spun ribbons underwent thermal-elastic martensitic transformation and reverse transformation in cooling and heating process and exhibited typical thermo-elastic shape memory effect. However the start temperature for martensitic transformation decreased from 286 K for as-cast alloy to 254 K for as-quenched ribbon and Curie temperature remains approximately constant. A particular internal stress induced by melt-spinning resulted in the formation of a texture structure in the ribbons, which made the ribbons obtain larger martensitic transformation strain and MFIS. The internal stress was released substantially after annealing, which resulted in a decrease of MFIS of the ribbons.

Preparation of AZ91D magnesium alloy semi-solid billet by new strain induced melt activated method

New strain induced melt activated (new SIMA) method for preparing AZ91D magnesium alloy semi-solid billet is introduced by applying equal channel angular extrusion into strain induced step in SIMA method, by which semi-solid billet with fine spheroidal grains and average grain size of 18 μm can be prepared. Furthermore, average grain size of semi-solid billet is reduced with increasing extrusion pass of AZ91D magnesium alloy obtained in ECAE process. By using semi-solid billet prepared by new SIMA, thixoforged magazine plates component with high mechanical properties such as yield strength of 201.4 MPa, ultimate tensile strength of 321.8 MPa and elongation of 15.3%, can be obtained.

MODELING OF STRAIN-INDUCED PRECIPITATION KINETICS IN Nb MICROALLOYED STEELS

On the basis of the thermodynamic calculation of precipitation and considering the effect of strain on the precipitation behavior and chemical composition （Si and Mn）, the kinetics of precipitation from austenite has been investigated for different temperatures and strains. Nucleation theory and the solubility product of niobium, carbon, and nitrogen in austenite have been used to derive equations for the start time of precipitation as a function of temperature and composition. The value of n in Avrami equation was determined using the available experimental data from the published reports, which indicated that n is a constant independent of temperature and the end time of precipitation is a function of n and the start time of precipitation. The values of the start time and end time of precipitation predicted by the new model are compared with the experimental values and a good agreement was obtained between both.

Large magnetic-field-induced strains in rare earth polycrystalline Ni-Mn-Ga

The magnetic-field-induced strains (MFIS) of polycrystallineNi_(50)Mn_(29)Ga_(21) alloys containing Tb were studied. A large MFIS of -1.10% was obtained undercompressi ve prestress conditions. The addition of Tb can fine the crystal grains, enhance thebending strength obviously, and make MFIS increase further, indicating that a moderate amount of Tbdoes not hinder twin boundary motion and it conversely makes the material more practical.

Martensitic Transformation and Magnetic-Field-Induced Strain in Ni-Mn-Ga-RE (RE=Tb, Sm) Alloys

The effects of microamount additions of RE (Tb, Sm) on martensitic transition, the magnetic-field-induced strain and the bending strength of highly textured polycrystalline Ni_(48)Mn_(33)Ga_(19) alloy were investigated. The experimental results show that the addition of RE elements decreases the martensitic transformation temperature and the Curie temperature. But the bending strength of Ni-Mn-Ga-RE (RE=Tb, Sm) alloys increases remarkably because of the grain refinement. As a result, Ni-Mn-Ga-RE alloys will be applied practically with higher reliability and stability due to favorable plasticity and toughness. In addition, the replacement of small amounts Ga by Tb or Sm decreases the magnetic-field-induced strain of the alloys at room temperature.

TUDY OFSTRAIN INDUCED MARTENSITE TRANSFORMATION FOR A MEDIUM MANGANE SESTEEL

The distribution of Cand Mn atomsinthe austenitic matrix isheterogeneous,the Mn atoms tendtooccupythefirst neighbour position ofthe Catomsin theaustenite. During deforma tion thethreekindsof martensitearestraininduced , havinginternal magneticfield valuese qualto33 0T, 30 5Tand 28 2Trespectively, andthe martensiteisstraininduced firstin the austenitecontainingless Cand Mn atoms.

A CONTINUUM MODEL FOR AXIAL-STRAIN-INDUCED TORSION IN SINGLE-WALL CARBON NANOTUBES

Using the atomistic-based finite-deformation shell theory, we analytically investigate the coupling between the axial deformation and the torsion in single-wall carbon nanotubes. We find that the axial-strain-induced torsion（ASIT） response is limited only to chiral nanotubes. This response is affected by chiralities and radii of carbon nanotubes. Our results are similar to that of molecular dynamic simulations reported in the literatures.

SOCS3 Expression Correlates with Severity of Inflammation in Mouse Hepatitis Virus Strain 3-induced Acute Liver Failure and HBV-ACLF

Summary： Recently, suppressor of cytokine signaling-3 （SOCS3） has been shown to be an inducible endogenous negative regulator of Janus kinase/signal transducers and activators of transcription （JAK/STAT） pathway which is relevant in inflammatory response, while its functions in acute liver failure and HBV-induced acute-on-chronic liver failure （HBV-ACLF） have not been fully elucidated. In this study, we explored the role of SOCS3 in the development of mouse hepatitis virus strain 3 （MHV-3）-induced acute liver failure and its expression in liver and peripheral blood mononuclear cells （PBMCs） of patients with HBV-ACLF. Inflammation-related gene expression was detected by real-time PCR, immtmohistochemistry and Western blotting. The correlation between SOCS3 level and liver injury was studied. Our results showed that the SOCS3 expression was significantly elevated in both the liver tissue and PBMCs from patients with HBV-ACLF compared to mild chronic hepatitis B （CHB）. Moreover, a time course study showed that SOCS3 level was increased remarkably in the liver of BALB/cJ mice at 72 h post-infection. Pro-inflammatory cytokines, interleukin （IL）-1 β, IL-6, and tumor necrosis factor （TNF）-α, were also increased significantly at 72 h post-infection. There was a close correlation between hepatic SOCS3 level and IL-6, and the severity of liver injury defined by alanine aminotransferase （ALT） and aspartate aminotransferase （AST） levels, respectively. These data suggested that SOCS3 may play a pivotal role in the pathogenesis of MHV-3-induced acute liver failure and HBV-ACLF.

Strain-induced Microstructural Changes and Effects of Alloying Elements for Fe_3Al-based Alloys

The strain-induced microstructural changes of Fe3Al-based alloys during room temperature deformation and high temperature creep were investigated. The results illustrated the strain-induced disor dering occured during room temperature deformation. Creep strain could induced two opposite processes, which are strain-induced disordering and creep recovery-induced reordering. These two opposite creep induced processes during creep result in reducing the influence of primary microstructure on the rupture life.

Strain-induced ferroelectric phase transitions in incipient ferroelectric rutile TiO_2

Uniaxial strain induced ferroelectric phase transitions in rutile TiO2 are investigated by first-principles calculations. The calculated results show that the in-plane tensile strain induces rutile TiO2, paraelectric phase with P4-2/mnm （D4h） space group, to a ferroelectric phase with Pm（Cs） space group, driven by the softening behaviour of the Eul mode. In addition, the out-of-plane tensile strain, vertical to the ab plane, leads to a ferroelectric phase with P42nm （C4v） space group, driven by the softening behaviour of the A2u mode. The critical tensile strains are 3.7% in-plane and 4.0% out-of-plane, respectively. In addition, the in-plane compression strain, which has the same structure variation as out- of-plane tensile strain due to Poisson effect, leads the paraelectric rutile TiO2 to a paraelectric phase with Pnnm （D2h） space group driven by the softening behaviour of the B1g mode. These results indicate that the sequence ferroelectric （or paraelectric） phase depends on the strain applied. The origin of ferroelectric stabilization in rutile TiO2 is also discussed briefly in terms of strain induced Born effective charge transfer.

Influence of Carbides and Strain-induced Martensite on Wear Resistance of Austenitic Medium Manganese Steels

The abrasive wear behaviour of austenitic medium manganese steels was studied under weak corrosion-abrasive wear simulating the liner plate in wet metallic ore bail mill under non-severe impact-loading working condition. Results show that the work-hardening mechanism and the wear resistance of high carbon austenitic medium manganese steels differ from those of medium carbon austenitic medium manganese steel. Under non-severe impact and weak corrosion-abrasive wear,the wear resistances of high carbon and medium carbon austenitic medium manganese steels are 50-90% and 20-40% higher than that of Hadfield steel respectively.

Flow stress model considering the transformation-induced plasticity effect and the inelastic strain recovery behavior

On the basis of continuum mechanics and the Mori-Tanaka mean field theory, a micro-mechanical flow stress model that considered both the transformation-induced plasticity （TRIP） effect and the inelastic strain recovery behavior of TRIP multiphase steels was presented. The relation between the volume fraction of constituent phases and plastic strain was introduced to characterize the transformation-induced plasticity effect of TRIP steels. Loading-unloading-reloading uniaxial tension tests of TRIP600 steel were carried out and the strain recovery behavior after unloading was analyzed. From the experimental data, an empirical elastic modulus expression is extracted to characterize the inelastic strain recovery. A comparison of the predicted flow stress with the experimental data shows a good agreement. The mechanism of the transformation-induced plasticity effect and the inelastic recovery effect acting on the flow stress is also discussed in detail.

KINETICS OF STRAIN-INDUCED PRECIPITATION OF (Nb,V) CARBONITRIDE IN A MICROALLOYED STEEL

The kinetics of the isothermal precipitation of(Nb,V)CN in Nb-V alloys has been investi- gated by using the Formastor-press simulator and the extraction replica method.Under four deformation amounts(0,10,30,50%)and three temperatures(1100,1000,850℃), four types of kinetic curves were found.

Characteristics of Strain-Induced Ferrite in Low Carbon Steel

The strain-induced ferrite formed under different conditions was observed with SEM and optical microscope.The nucleation sites of strain-induced ferrite include grain boundary,grain inside,deformed band and annealing twin boundary.The shapes of the ferrite accordingly are equiaxed irregular polygonal,strip-shaped and acicular.