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.

Austempering of hot rolled transformation-induced plasticity steels

Thermomechanical controlled processing (TMCP) was conducted by using a laboratory hot rolling mill. Austempering in the salt bath after hot rolling was investigated. The effect of isothermal holding time on mechanical properties was studied through examining of the microstructure and mechanical properties of the specimens. The mechanism of transformation-induced plasticity (TRIP) was discussed. The results show that the microstructure of these steels consists of polygonal ferrite, granular bainite, and a significant amount of stable retained austenite. Strain-induced transformation to martensite of retained austenite and TRIP occur in the hot rolled Si-Mn TRIP steels. Excellent mechanical properties were obtained for various durations at 400°C. Prolonged holding led to cementite precipitation, which destabilized the austenite. The mechanical properties were optimal when the specimen was held for 25 min, and the tensile strength, total elongation, and strength ductility balance reached the maximum values of 776 MPa, 33%, and 25608 MPa?%, respectively.

Effect of deformation temperature on transformation-induced plasticity effect of lean duplex stainless steel

Effects of deformation temperature on the mechanical properties and microstructure of lean duplex stainless steels B2102 and $32101 have been investigated.It was found that the strength decreased continuously with increases in temperature from-60 ℃ to 100 ℃.The strength of $32101 was higher than that of B2102 owing to its higher nitrogen content.Plasticity of B2102 increased with an increase in deformation temperature from-60 ℃ and reached the optimal elongation ratio of 49%-54% after deformation at 20-50 ℃.Martensite transformation was observed during deformation due to the transformation-induced plasticity effect.The optimal elongation was achieved at deformation temperatures close to the M_d(30/50) temperatures of 62℃ and 6℃ for B2102 and S32101,respectively.

Break the strength-ductility trade-off in a transformation-induced plasticity high-entropy alloy reinforced with precipitation strengthening

Transformation-induced plasticity(TRIP)endows material with continuous work hardening ability,which is considered as a powerful weapon to break the strength-ductility tradeoff.However,FCC based alloys with TRIP effect can not get rid of the“soft”feature of the structure entirely,resulting in insufficient yield strength.Here,a Co_(x)Cr_(25)(AlFeNi)_(75-x) high-entropy alloy is designed.NiAl phase is used as strengthening component to improve yield strength,while TRIP effect ensures plasticity.Compared with the previous TRIP high-entropy alloy,its yield strength is nearly doubled,and the uniform elongation is more than 55%at room temperature.Furthermore,the corresponding multiphase microstructure evolution and deformation mechanisms are investigated.Significantly,stacking faults andΣ3 twin boundaries are confirmed to be the nucleation sites of HCP phase by HAADF-STEM.Ingenious composition design and proper heat treatment process make it a perfect combination of precipitation strengthening and transformationinduced plasticity,and thus guide design in the high-performance alloy.

Enhancement of ballistic performance enabled by transformation-induced plasticity in high-strength bainitic steel

High-strength bainitic steels have created a lot of interest in recent times because of their excellent combination of strength,ductility,toughness,and high ballistic mass efficiency.Bainitic steels have great potential in the fabrication of steel armor plates.Although various approaches and methods have been conducted to utilize the retained austenite(RA)in the bainitic matrix to control mechanical properties,very few attempts have been conducted to improve ballistic performance utilizing transformationinduced plasticity(TRIP)mechanism.In this study,high-strength bainitic steels were designed by controlling the time of austempering process to have various volume fractions and stability of RA while maintaining high hardness.The dynamic compressive and ballistic impact tests were conducted,and the relation between the effects of TRIP on ballistic performance and the adiabatic shear band(ASB)formation was analyzed.Our results show for the first time that an active TRIP mechanism achieved from a large quantity of metastable RA can significantly enhance the ballistic performance of high-strength bainitic steels because of the improved resistance to ASB formation.Thus,the ballistic performance can be effectively improved by a very short austempering time,which suggests that the utilization of active TRIP behavior via tuning RA acts as a primary mechanism for significantly enhancing the ballistic performance of high-strength bainitic steels.

Surface effect induced phase transformation by Mn removal during annealing and its textures in cold-rolled high manganese transformation-induced plasticity steel

The surface effect induced transformation texture during vacuum annealing of cold-rolled high manganese transformation-induced plasticity(TRIP)steels was studied.Due to Mn removal occurring at the surface layer,γ→δdiffusional phase transformation leads to the formation of hard pancake-shaped ferrite grains due to solution strengthening at the surface and the centre layer remains as austenite+martensite after annealing.In the case of slow heating,{112}/{111}<110>textures for the surface ferrite were strengthened with the increase in temperature and holding time,indicating an inheritance of rolling textures.By increasing the heating rate of annealing,the rotated cube texture was developed in surface ferrite.This kind of multiphase sandwich structure with hard ferrite surface layer and tough austenite dominant centre can increase tensile strength and should also improve deep drawing properties,therefore providing new possibility of controlling properties for the application of high manganese TRIP steel.

Perspectives in human brain plasticity sparked by glioma invasion:from intraoperative(re)mappings to neural reconfigurations

Exploring the aptitude of the human brain to compensate functional consequences of a lesion damaging its structural architecture is a key challenge to improve patient care in various neurological diseases,to optimize neuroscientifically-informed strategies of postlesional rehabilitation,and ultimately to develop innovative neuro-regenerative therapies.The term‘plasticity’,initially referring to the intrinsic propensity of neurons to modulate their synaptic transmission in a learning situation,was progressively transposed to brain injury research and clinical neurosciences.Indeed,in the event of brain damage,adaptive mechanisms of compensation allow a partial reshaping of the structure and activities of the central nervous system,thus permitting to some extent the maintenance of brain functions.

Mitochondrial recruitment in myelin:an anchor for myelin dynamics and plasticity?

Optimal propagation of neuronal electrical impulses depends on the insulation of axons by myelin,produced in the central nervous system by oligodendrocytes.Myelin is an extension of the oligodendrocyte plasma membrane,which wraps around an axon to form a compact multi-layered sheath.Myelin is composed of a substantially higher proportion of lipids compared to other biological membranes and enriched in a small number of specialized proteins.

Glial progenitor heterogeneity and plasticity in the adult spinal cord

Glial progenitor cells were reported to have the capacity to generate various types of cells in both the central nervous system(CNS)and peripheral nervous system.Glial progenitor cells can respond to diverse environmental signals and transform into distinct populations,each serving specific functions.Notably,the adult spinal cord hosts various populations of glial progenitors,a region integral to the central nervous system.During development,glial progenitors express glial fibrillary acidic protein(GFAP;Dimou and Gotz,2014).However,the specific identities of GFAP-expressing progenitors in the adult spinal cord were not thoroughly investigated.

Timing effect of high temperature exposure on the plasticity of internode and plant architecture in maize

The occurrence of high temperature(HT)in crop production is becoming more frequent and unpredictable with global warming,severely threatening food security.The state of an organ’s growth and development is largely determined by the temperature conditions it is exposed to over time.Maize is the main cereal crop,and its stem growth and plant architecture are closely related to lodging resistance,and especially sensitive to temperature.However,systematic research on the timing effect of HT on the sequentially developing internode and stem is currently lacking.To identify the timing effect of HT on the morphology and plasticity of the stem in maize,two hybrids(Zhengdan 958(ZD958),Xianyu 335(XY335))characterized by distinct morphological traits in the stem were exposed to a 7-day HT treatment from the V6 to V17 stages(Vn presents the vegetative stage with n leaves fully expanded)in 2019-2020.The results demonstrated that exposure to HT during V6-V12 accelerated the rapid elongation of stems.For instance,HT occurring at V7 and V12 specifically promoted the lengths and weights of the 3rd-5th and 9th-11th internodes,respectively.Meanwhile,HT slowed the growth of internodes adjacent to the promoted internodes.Interestingly,compared with control,the plant height was significantly increased soon after HT treatment,but the promotion effect became narrower at the subsequent flowering stage,demonstrating a self-adjusting mechanism in the maize plant in response to HT.Importantly,HT altered the plant architectures,including a rising of the ear position and increase in the ear position coefficient.XY335 exhibited greater sensitivity in stem development than ZD958 under HT treatment.These findings improve our systematic understanding of the plasticity of internode and plant architecture in response to the timing of HT exposure.

Superplasticity of fine-grained Mg-10Li alloy prepared by severe plastic deformation and understanding its deformation mechanisms

The superplastic behavior and associated deformation mechanisms of a fine-grained Mg-10.1 Li-0.8Al-0.6Zn alloy(LAZ1011)with a grain size of 3.2μm,primarily composed of the BCCβphase and a small amount of the HCPαphase,were examined in a temperature range of 473 K to 623 K.The microstructural refinement of this alloy was achieved by employing high-ratio differential speed rolling.The best superplasticity was achieved at 523 K and at strain rates of 10^(-4)-5×10^(-4)s^(-1),where tensile elongations of 550±600%were obtained.During the heating and holding stage of the tensile samples prior to tensile loading,a significant increase in grain size was observed at temperatures above 573 K.Therefore,it was important to consider this effect when analyzing and understanding the superplastic deformation behavior and mechanisms.In the investigated strain rate range,the superplastic flow at low strain rates was governed by lattice diffusion-controlled grain boundary sliding,while at high strain rates,lattice diffusion-controlled dislocation climb creep was the rate-controlling deformation mechanism.It was concluded that solute drag creep is unlikely to occur.During the late stages of deformation at 523 K,it was observed that grain boundary sliding led to the agglomeration of theαphase,resulting in significant strain hardening.Deformation mechanism maps were constructed forβ-Mg-Li alloys in the form of 2D and 3D formats as a function of strain rate,stress,temperature,and grain size,using the constitutive equations for various deformation mechanisms derived based on the data of the current tests.

Anelasticity to plasticity transition in a model two-dimensional amorphous solid

Anelasticity, as an intrinsic property of amorphous solids, plays a significant role in understanding their relaxation and deformation mechanism. However, due to the lack of long-range order in amorphous solids, the structural origin of anelasticity and its distinction from plasticity remain elusive. In this work, using frozen matrix method, we study the transition from anelasticity to plasticity in a two-dimensional model glass. Three distinct mechanical behaviors, namely,elasticity, anelasticity, and plasticity, are identified with control parameters in the amorphous solid. Through the study of finite size effects on these mechanical behaviors, it is revealed that anelasticity can be distinguished from plasticity.Anelasticity serves as an intrinsic bridge connecting the elasticity and plasticity of amorphous solids. Additionally, it is observed that anelastic events are localized, while plastic events are subextensive. The transition from anelasticity to plasticity is found to resemble the entanglement of long-range interactions between element excitations. This study sheds light on the fundamental nature of anelasticity as a key property of element excitations in amorphous solids.

Neural stem cells promote neuroplasticity: a promising therapeutic strategy for the treatment of Alzheimer’s disease

Recent studies have demonstrated that neuroplasticity,such as synaptic plasticity and neurogenesis,exists throughout the normal lifespan but declines with age and is significantly impaired in individuals with Alzheimer’s disease.Hence,promoting neuroplasticity may represent an effective strategy with which Alzheimer’s disease can be alleviated.Due to their significant ability to self-renew,differentiate,and migrate,neural stem cells play an essential role in reversing synaptic and neuronal damage,reducing the pathology of Alzheimer’s disease,including amyloid-β,tau protein,and neuroinflammation,and secreting neurotrophic factors and growth factors that are related to plasticity.These events can promote synaptic plasticity and neurogenesis to repair the microenvironment of the mammalian brain.Consequently,neural stem cells are considered to represent a potential regenerative therapy with which to improve Alzheimer’s disease and other neurodegenerative diseases.In this review,we discuss how neural stem cells regulate neuroplasticity and optimize their effects to enhance their potential for treating Alzheimer’s disease in the clinic.

3'-Deoxyadenosin alleviates methamphetamine-induced aberrant synaptic plasticity and seeking behavior by inhibiting the NLRP3 inflammasome

Methamphetamine addiction is a brain disorder characterized by persistent drug-seeking behavior, which has been linked with aberrant synaptic plasticity. An increasing body of evidence suggests that aberrant synaptic plasticity is associated with the activation of the NOD-like receptor family pyrin domain containing-3(NLRP3) inflammasome. 3′-Deoxyadenosin, an active component of the Chinese fungus Cordyceps militaris, has strong anti-inflammatory effects. However, whether 3′-deoxyadenosin attenuates methamphetamine-induced aberrant synaptic plasticity via an NLRP3-mediated inflammatory mechanism remains unclear. We first observed that 3′-deoxyadenosin attenuated conditioned place preference scores in methamphetamine-treated mice and decreased the expression of c-fos in hippocampal neurons. Furthermore, we found that 3′-deoxyadenosin reduced the aberrant potentiation of glutamatergic transmission and restored the methamphetamine-induced impairment of synaptic plasticity. We also found that 3′-deoxyadenosin decreased the expression of NLRP3 and neuronal injury. Importantly, a direct NLRP3 deficiency reduced methamphetamine-induced seeking behavior, attenuated the impaired synaptic plasticity, and prevented neuronal damage. Finally, NLRP3 activation reversed the effect of 3′-deoxyadenosin on behavior and synaptic plasticity, suggesting that the anti-neuroinflammatory mechanism of 3′-deoxyadenosin on aberrant synaptic plasticity reduces methamphetamine-induced seeking behavior. Taken together, 3′-deoxyadenosin alleviates methamphetamine-induced aberrant synaptic plasticity and seeking behavior by inhibiting the NLRP3 inflammasome.

Temperature dependence of Lüders strain and its correlation with martensitic transformation in a medium Mn transformation-induced plasticity steel

The Lüders deformation behavior in a medium Mn transformation-induced plasticity(TRIP)steel is investigated at different temperatures ranging from 25 to 300°C.It demonstrates that the Lüders band appears at all testing temperatures but with varied Lüders strains which do not change monotonically with temperature.The martensitic transformation is simultaneously observed within the Lüders band in varying degrees depending on the testing temperature.It is well verified that the martensitic transformation is not responsible for the formation of Lüders band,and a reasonable explanation is given for the non-monotonic variation of Lüders strain with increasing temperature.

Assessment of a two-surface plasticity model for hexagonal materials

A computationally efficient two-surface plasticity model is assessed against crystal plasticity. Focus is laid on the mechanical behavior of magnesium alloys in the presence of ductility-limiting defects, such as voids. The two surfaces separately account for slip and twinning such that the constitutive formulation captures the evolving plastic anisotropy and evolving tension-compression asymmetry. For model identification, a procedure is proposed whereby the initial guess is based on a combination of experimental data and computationally intensive polycrystal calculations from the literature. In drawing direct comparisons with crystal plasticity, of which the proposed model constitutes a heuristically derived reduced-order model, the available crystal plasticity simulations are grouped in two datasets. A calibration set contains minimal data for both pristine and porous material subjected to one loading path. Then the two-surface model is assessed against a broader set of crystal plasticity simulations for voided unit cells under various stress states and two loading orientations. The assessment also includes microstructure evolution(rate of growth of porosity and void distortion). The ability of the two-surface model to capture essential features of crystal plasticity is analyzed along with an evaluation of computational cost. The prospects of using the model in guiding the development of physically sound damage models in Mg alloys are put forth in the context of high-throughput simulations.

Astrocyte-neuron communication mediated by the Notch signaling pathway:focusing on glutamate transport and synaptic plasticity

Maintaining glutamate homeostasis after hypoxic ischemia is important for synaptic function and neural cell activity,and regulation of glutamate transport between astrocyte and neuron is one of the important modalities for reducing glutamate accumulation.However,further research is needed to investigate the dynamic changes in and molecular mechanisms of glutamate transport and the effects of glutamate transport on synapses.The aim of this study was to investigate the regulatory mechanisms underlying Notch pathway mediation of glutamate transport and synaptic plasticity.In this study,Yorkshire neonatal pigs(male,age 3 days,weight 1.0–1.5 kg,n=48)were randomly divided into control(sham surgery group)and five hypoxic ischemia subgroups,according to different recovery time,which were then further subdivided into subgroups treated with dimethyl sulfoxide or a Notch pathway inhibitor(N-[N-(3,5-difluorophenacetyl-l-alanyl)]-S-phenylglycine t-butyl ester).Once the model was established,immunohistochemistry,immunofluorescence staining,and western blot analyses of Notch pathway-related proteins,synaptophysin,and glutamate transporter were performed.Moreover,synapse microstructure was observed by transmission electron microscopy.At the early stage(6–12 hours after hypoxic ischemia)of hypoxic ischemic injury,expression of glutamate transporter excitatory amino acid transporter-2 and synaptophysin was downregulated,the number of synaptic vesicles was reduced,and synaptic swelling was observed;at 12–24 hours after hypoxic ischemia,the Notch pathway was activated,excitatory amino acid transporter-2 and synaptophysin expression was increased,and the number of synaptic vesicles was slightly increased.Excitatory amino acid transporter-2 and synaptophysin expression decreased after treatment with the Notch pathway inhibitor.This suggests that glutamate transport in astrocytes-neurons after hypoxic ischemic injury is regulated by the Notch pathway and affects vesicle release and synaptic plasticity through the expression of synaptophysin.

Repetitive transcranial magnetic stimulation promotes neurological functional recovery in rats with traumatic brain injury by upregulating synaptic plasticity-related proteins

Studies have shown that repetitive transcra nial magnetic stimulation(rTMS)can enhance synaptic plasticity and improve neurological dysfunction.Howeve r,the mechanism through which rTMS can improve moderate traumatic brain injury remains poorly understood.In this study,we established rat models of moderate traumatic brain injury using Feeney's weight-dropping method and treated them using rTMS.To help determine the mechanism of action,we measured levels of seve ral impo rtant brain activity-related proteins and their mRNA.On the injured side of the brain,we found that rTMS increased the protein levels and mRNA expression of brain-derived neurotrophic factor,tropomyosin receptor kinase B,N-methyl-D-aspartic acid receptor 1,and phosphorylated cAMP response element binding protein,which are closely associated with the occurrence of long-term potentiation.rTMS also partially reve rsed the loss of synaptophysin after injury and promoted the remodeling of synaptic ultrastructure.These findings suggest that upregulation of synaptic plasticity-related protein expression is the mechanism through which rTMS promotes neurological function recovery after moderate traumatic brain injury.

Boosting corticospinal system synaptic plasticity to recover motor functions

An importa nt strategy to promote voluntary movements after motor system injury is to strengthen the connections between the motor cortex and muscles by taking advantage of the plasticity of the corticospinal motor system.Many neuromodulation approaches are directed to activate the spinal cord and peripheral axons to strengthen muscle activation.We discuss in this perspective that,the cortex and spinal cord should be ta rgeted together to enhance cortex-to-musclefunction(Amer and Martin,2022).

Neuroplastin in Ca^(2+)signal regulation and plasticity of glutamatergic synapses

The main function of neurons is information transmission in the form of action potentials.To fulfill this duty,neurons are connected functionally with each other via synapses,the microscopic structures where specialized molecular machinery is strategically placed to release and receive neurotransmitters and to generate and extinguish calcium(Ca^(2+))signals.These synaptic molecular components are highly dynamic and they influence each other to confer structural and functional adaptability(plasticity)to neuronal communication(Biederer et al.,2017).