Evolution of microstructure and properties of a novel Ni-based superalloy during stress relief annealing

We discussed the decrease in residual stress,precipitation evolution,and mechanical properties of GH4151 alloy in different annealing temperatures,which were studied by the scanning electron microscope(SEM),high-resolution transmission electron microscopy(HRTEM),and electron backscatter diffraction(EBSD).The findings reveal that annealing processing has a significant impact on diminishing residual stresses.As the annealing temperature rose from 950 to 1150℃,the majority of the residual stresses were relieved from 60.1 MPa down to 10.9 MPa.Moreover,the stress relaxation mechanism transitioned from being mainly controlled by dislocation slip to a combination of dislocation slip and grain boundary migration.Meanwhile,the annealing treatment promotes the decomposition of the Laves,accompanied by the precipitation ofμ-(Mo_(6)Co_(7))starting at 950℃ and reaching a maximum value at 1050℃.The tensile strength and plasticity of the annealing alloy at 1150℃ reached the maximum(1394 MPa,56.1%)which was 131%,200%fold than those of the as-cast alloy(1060 MPa,26.6%),but the oxidation process in the alloy was accelerated at 1150℃.The enhancement in durability and flexibility is primarily due to the dissolution of the brittle phase,along with the shape and dispersal of theγ′phase.

Effect of quenching cooling rate on residual stress and microstructure evolution of 6061 aluminum alloy

In this study,the cooling rate was manipulated by quenching with water of different temperatures(30,60 and 100℃).Surface and internal residual stresses in the quenched 6061 aluminum alloy samples were measured using hole-drilling and crack compliance methods,respectively.Then,the processability of the quenched samples was evaluated at cryogenic temperatures.The mechanical properties of the as-aged samples were assessed,and microstructure evolution was analyzed.The surface residual stresses of samples W30℃,W60℃and W100℃is−178.7,−161.7 and−117.2 MPa,respectively along x-direction,respectively;and−191.2,−172.1 and−126.2 MPa,respectively along y-direction.The sample quenched in boiling water displaying the lowest residual stress(~34%and~60%reduction in the surface and core).The generation and distribution of quenching residual stress could be attributed to the lattice distortion gradient.Desirable plasticity was also exhibited in the samples with relatively low quenching cooling rates at cryogenic temperatures.The strengthes of the as-aged samples are 291.2 to 270.1 MPa as the quenching water temperature increase from 30℃to 100℃.Fine and homogeneous β"phases were observed in the as-aged sample quenched with boiling water due to the clusters and Guinier-Preston zones(GP zones)premature precipitated during quenching process.

Characteristic stress variation and microcrack evolution of granite subjected to uniaxial compression using acoustic emission methods

The size of mineral grain has a significant impact on the initiation and propagation of microcracks within rocks.In this study,fine-,medium-,and coarse-grained granites were used to investigate microcrack evolution and characteristic stress under uniaxial compression using the acoustic emission(AE),digital image correlation(DIC),and nuclear magnetic resonance(NMR)measurements.The experimental results show that the characteristic stress of each granite decreased considerably with increasing grain sizes.The inflection points of the b-value occurred earlier with an increase in grain sizes,indicating that the larger grains promote the generation and propagation of microcracks.The distribution characteristics of the average frequency(AF)and the ratio of rise time to amplitude(RA)indicate that the proportion of shear microcracks increases with increasing grain size.The NMR results indicate that the porosity and the proportion of large pores increased with increasing grain size,which may intensify the microcrack evolution.Moreover,analysis of the DIC and AE event rates suggests that the high-displacement regions could serve as a criterion for the degree of microcrack propagation.The study found that granites with larger grains had a higher proportion of high-displacement regions,which can lead to larger-scale cracking or even spalling.These findings are not only beneficial to understand the pattern of microcrack evolution with different grain sizes,but also provide guidance for rock monitoring and instability assessment.

Shear band evolution and acoustic emission characteristics of sandstone containing non-persistent flaws

Direct shear tests were conducted on sandstone specimens under different constant normal stresses to study the coalescence of cracks between non-persistent flaws and the shear sliding characteristics of the shear-formed fault.Digital image correlation and acoustic emission(AE)techniques were used to monitor the evolution of shear bands at the rock bridge area and microcracking behaviors.The experimental results revealed that the shear stresses corresponding to the peak and sub-peak in the stressdisplacement curve are significantly affected by the normal stress.Strain localization bands emerged at both the tip of joints and the rock bridge,and their extension and interaction near the peak stress caused a surge in the AE hit rate and a significant decrease in the AE b value.Short and curvilinear strain bands were detected at low normal stress,while high normal stress generally led to more microcracking events and longer coplanar cracks at the rock bridge area.Furthermore,an increase in normal stress resulted in a higher AE count rate and more energetic AE events during friction sliding along the shearformed fault.It was observed that the elastic energy released during the crack coalescence at the prepeak stage was much greater than that released during friction sliding at the post-peak stage.More than 75%of AE events were located in the low-frequency band(0e100 kHz),and this proportion continued to rise with increasing normal stress.Moreover,more AE events of low AF value and high RA value were observed in specimens subjected to high normal stress,indicating that greater normal stress led to more microcracks of shear nature.

Effects of Light Stress on Oxygen Evolution and Photochemical Energy Stor age of Hybrid Poplar Clones Determined by Photoacoustic Technique

The oxygen evolution, thermal dissipation, and photochemical energy storage of three hybrid poplar clones, namely the triploid clone B342, the diploid clone B11 [(Populus alba×P. glandulosa)×(P.tomentosa×P.bolleana)], and the triploid clone B346 [(P.tomentosa×P. bolleana)×(P. alba×P.glandulosa)], under light stress were studied using photoacoustics. The oxygen evolution signal and photochemical energy storage varied negatively with the pretreatment_PFD (photon flux density), whereas the thermal signal varied positively with the pretreatment_PFD. Photochemical energy storage was reallocated to PSⅡ more than to PSⅠ, while the photochemical energy storage in PSⅠ was more stable than that in PSⅡ when subjected to light stress. The inhibitors streptomycin (SM), dithiothreitol (DTT) and sodium fluoride (NaF) could all affect the oxygen evolution signal. Clones B11 and B342 were more resistant to light stress than clone B346.

Understand anisotropy dependence of damage evolution and material removal during nanoscratch of MgF_(2) single crystals

To understand the anisotropy dependence of the damage evolution and material removal during the machining process of MgF_(2) single crystals,nanoscratch tests of MgF_(2) single crystals with different crystal planes and directions were systematically performed,and surface morphologies of the scratched grooves under different conditions were analyzed.The experimental results indicated that anisotropy considerably affected the damage evolution in the machining process of MgF_(2) single crystals.A stress field model induced by the scratch was developed by considering the anisotropy,which indicated that during the loading process,median cracks induced by the tensile stress initiated and propagated at the front of the indenter.Lateral cracks induced by tensile stress initiated and propagated on the subsurface during the unloading process.In addition,surface radial cracks induced by the tensile stress were easily generated during the unloading process.The stress change led to the deflection of the propagation direction of lateral cracks.Therefore,the lateral cracks propagated to the workpiece surface,resulting in brittle removal in the form of chunk chips.The plastic deformation parameter indicated that the more the slip systems were activated,the more easily the plastic deformation occurred.The cleavage fracture parameter indicated that the cracks propagated along the activated cleavage planes,and the brittle chunk removal was owing to the subsurface cleavage cracks propagating to the crystal surface.Under the same processing parameters,the scratch of the(001)crystal plane along the[100]crystal-orientation was found to be the most conducive to achieving plastic machining of MgF_(2) single crystals.The theoretical results agreed well with the experimental results,which will not only enhance the understanding of the anisotropy dependence of the damage evolution and removal process during the machining of MgF_(2) crystals,but also provide a theoretical foundation for achieving the high-efficiency and low-damage processing of anisotropic single crystals.

Stress evolution and support mechanism of a bolt anchored in a rock mass with a weak interlayer

By applying experimental method, the bolt stress and supporting mechanism is studied during the deformation process of a rock mass containing a weak interlayer. The force measuring bolt is installed manually and instrumented five pairs of symmetrical strain gauges. The experimental results show that the fully grouted bolt suffers tensile, compressive, bending and shear stress at the same time. The bolt stress evolution is closely related to the deformation stages of the rock mass which are very gradually varying stage, gradually varying stage at the pre-peak and suddenly varying stage at the post peak stage.The axial compressive stress in the bolt is mainly induced by the moment. Thus, in most cases the axial compressive stress is distributed on one side of the bolt. For axial stresses, induced by the axial force and the bending moment at the post-peak stage, three types of changing are observed, viz. increasingincreasing type, decreasing-increasing type and increasing-decreasing type. The stress characteristics of the bolt section in the weak interlayer are significantly different from those in the hard rock. The failure models of the anchored bolt are tensile failure and shear failure, respectively. The bolt not only provides constraints on the free surface of the rock mass, but also resists the axial and lateral loading by the bending moment. This study provides valuable guidelines for bolting support design and its safety assessment.

Stress evolution and failure process of Brazilian disc under impact

To reveal stress distribution and crack propagation of Brazilian discs under impact loads, dynamic tests were conducted with SHPB （split Hopkinson pressure bar） device. Stress states of specimens were monitored with strain gauges on specimen surface and SHPB bars. The failure process of specimen was recorded by ultra speed camera FASTCAM SAI.1 （675 000 fps）. Stress histories from strain gauges offer comprehensive information to evaluate the stress equilibrium of specimen in time and space. When a slowly rising load （with loading rates less than 1 200 N/s for d 50 mm bar） is applied, there is usually good stress equilibrium in specimen. The stress distribution after equilibrium is similar to its static counterpart. And the first crack initiates at the disc center and propagates along the load direction. But with the front of incident wave becoming steep, it is hard for specimens to get to stress equilibrium. The first crack may appear anywhere on the specimen together with multiple randomly distributed secondary cracks. For a valid dynamic Brazil test with stress equilibrium, the specimen will break into two halves neatly. While for tests with stress disequilibrium, missing strap may be found when broken halves of specimens are put together. For those specimens broken up neatly at center but having missing wedges at the loading areas, it is usually subjected to local buckling from SHPB bars.

Stress evolution of deep surrounding rock under characteristics of bi-modulus and strength drop

Aiming at the circular chamber under uniform stress field in deep energy storage and mining,analytical solutions of stress and plastic zone of the surrounding rock under different far-field stress and internal pressure were derived based on bi-modulus theory and the elastic-brittle-ideal plastic constitutive model.Evolution trend of the elasticplastic stress and plastic region with different elastic constant ratios and residual strength coefficients were analyzed in details.Results revealed that when the internal pressure was small,the three-direction principal stress was compressive stress and the stress field distribution of the surrounding rock was not affected by the moduli difference.The obtained solution was consistent with the solution from the elastic-brittle plastic drop model under the equal modulus theory.On the other hand,when the internal pressure was large,the tangential stress was changed.The surrounding rock can be divided into three zones,i.e.,tensile plastic zone(TPZ),tensile elastic zone(TEZ)and compressive elastic zone(CEZ).The tensile and compressive dual modulus had significant influence on the demarcation point between TEZ and CEZ.In addition,the strength drop and the dual modulus characteristic had a coupling effect on the stress distribution in the surrounding rock.The related achievements further enrich the theory of deep rock mechanics.

Surrounding rock deformation and stress evolution in pre-driven longwall recovery rooms at the end of mining stage

Two case studies were conducted in the Shennan mining area of Shaanxi Province,China to evaluate the surrounding rock deformation and stress evolution in pre-driven longwall recovery rooms· These studies mainly monitored the surrounding rock deformation and coal pillar stress in the recovery rooms of the N1206 panel of 2-2 coal seam at Ningtiaota Coal Mine and the 15205 panel of 5-2 coal seam at Hongliulin Coal Mine.The monitoring results showed that the surrounding rock deformation of the main recovery room and the coal pillar stress in the N1206 and 15205 panels began to increase significantly when the face was 36 m and 42 m away from the terminal line,respectively.After the face entered the main recovery room,the maximum roof-to-floor convergence in the N1206 and 15205 panels was 348.03 mm and 771.24 mm,respectively,and the coal pillar stresses increased more than 5 MPa and 7 MPa,respectively.In addition,analysis of the periodic weighting data showed that the main roof break position of the N1206 and 15205 panels after the longwall face entered the main recovery room was-3.8 m and-8.2 m,respectively.This research shows that when the main roof breaks above the coal pillar,the surrounding rock deformation of the main recovery room and the coal pillar stress increase sharply.The last weighting is the key factor affecting the stability of the main recovery room and the coal pillar;main roof breaks at disadvantageous positions are the main cause of the support crushing accidents.

Effect of fatigue loading-confining stress unloading rate on marble mechanical behaviors: An insight into fracture evolution analyses

Rocks in underground works usually experience rather complex stress disturbance.For this,their fracture mechanism is significantly different from rocks subjected to conventional triaxial compression conditions.The effects of stress disturbances on rock geomechanical behaviors under fatigue loading conditions and triaxial unloading conditions have been reported in previous studies.However,little is known about the dependence of the unloading rate on fatigue loading and confining stress unloading(FL-CSU)conditions that influence rock failure.In this paper,we aimed at investigating the fracture behaviors of marble under FL-CSU conditions using the post-test X-ray computed tomography(CT)scanning technique and the GCTS RTR 2000 rock mechanics system.Results show that damage accumulation at the fatigue stage can influence the final fracture behaviors of marble.The stored elastic energy for rock samples under FL-CSU tests is relatively larger compared to those under conventional triaxial tests,and the dissipated energy used to drive damage evolution and crack propagation is larger for FL-CSU tests.In FL-CSU tests,as the unloading rate increases,the dissipated energy grows and elastic energy reduces.CT scanning after the test reveals the impacts of the unloading rate on the crack pattern and a fracture degree index is therein defined in this context to represent the crack dimension.It shows that the crack pattern after FL-CSU tests depends on the unloading rate,and the fracture degree is in agreement with the analysis of both the energy dissipation and the amount of energy released.The effect of unloading rate on fracture evolution characteristics of marble is revealed by a series of FL-CSU tests.

Microstructure evolution and its effect on flow stress of TC17 alloy during deformation in α+β two-phase region

The microstructure evolution and its effect on flow stress of TC17 alloy during deformation in the α+β two-phase region were investigated via microstructure characterization and isothermal compression tests. Results showed that the spheroidized rate of α phase at 820 and 850℃ slightly increased with increasing strain. With increasing deformation temperature, the spheroidized rate of α phase showed a slight increasing trend, but the volume fraction of α phase significantly decreased. The flow stress at 780 ℃ and 1 s^-1 decreased continuously and steady state condition was not achieved up to strain of 1.2 due to dislocation annihilation and α lamellae rotation. Under this condition, the dynamic spheroidization was retarded. At the deformation temperatures of 820 and 850℃, and a strain rate of 1 s^-1, a steady state flow stress was observed at strains above 0.8 due to the balance between work hardening and dynamic softening. The dynamic softening was attributed to the α lamellae rotation, dynamic recovery and a little spheroidization.

A Study on Dual-Load-Zone Model of Overlying Strata andEvolution Law of Mining Stress

The changeable structure and movement law of overlying strata are the maincontributor to the change of mining stress.Starting from the relevant theory of keystratum and particularly based on the theory of mine ground pressure and strata control,this research proposed a new solution to mining stress problems by establishing adual-load-zone stratum structural model.Elastic foundation beam theory was used tosolve the stress of overlying strata of the dual-load-zones with superposition method,which revised the traditional calculation method of mining stress.The abnormal increaseof lead abutment pressure in the mining area was explained effectively,through which theevolution law of mining stress in the case of hard rock was obtained.The results indicatethat mining stress experiences a drastic change within the range of 50 m ahead of the coalwall due to the collapse of main roof;under the influence of main key stratum andinferior key strata,the influence range of lead abutment pressure is extended up toapproximately 120 m in the working face;this remarkable increase can be attributed tothe excessive length of sagging zone.Results from both the dual-load-zone modelexperiment and field measurement demonstrate high consistency.The model can predictthe influence range of abutment pressure effectively and thus guide the safety productionof mining.

Breaking and mining-induced stress evolution of overlying strata in the working face of a steeply dipping coal seam

The breaking features and stress distribution of overlying strata in a steeply dipping coal seam(SDCS)differ significantly from those in a near-horizontal one.In this study,the laws governing the evolution of vertical stress release and shear stress concentration in the overlying strata of coal seams with different dip angles are derived via numerical simulation,rock mechanics tests,acoustic emissions,and field measurements.Thus,the stress-driven dynamic evolution of the overlying strata structure,in which a shear stress arch forms,is determined.Upon breaking the lower pari of the overlying strata,the shear stress transfers rapidly to the upper part of the working face.The damaged zone of the overlying strata migrates upward along the dip direction of the working face.The gangue in the lower part of the working face is compacted,leading to an increase in vertical stress.As the dip angle of the coal seam increases,the overlying strata fail suddenly under the action of shear stresses.Finally,the behavioral response of the overlying strata driven by shear stresses in the longwall working face of an SDCS is identified and analyzed in detail.The present research findings reveal the laws governing the behavior of mine pressure in the working face of an SDCS,which in turn can be used to establish the respective on-site guidance.

Evolutionary impacts of purine metabolism genes on mammalian oxidative stress adaptation

Many mammals risk damage from oxidative stress stemming from frequent dives(i.e., cycles of ischemia/reperfusion and hypoxia/reoxygenation),high altitude and subterranean environments, or powered flight. Purine metabolism is an essential response to oxidative stress, and an imbalance between purine salvage and de novo biosynthesis pathways can generate damaging reactive oxygen species(ROS). Here, we examined the evolution of 117 purine metabolism-related genes to explore the accompanying molecular mechanisms of enhanced purine metabolism in mammals under high oxidative stress. We found that positively selected genes,convergent changes, and nonparallel amino acid substitutions are possibly associated with adaptation to oxidative stress in mammals. In particular, the evolution of convergent genes with c AMP and c GMP regulation roles may protect mammals from oxidative damage. Additionally, 32 genes were identified as under positive selection in cetaceans, including key purine salvage enzymes(i.e., HPRT1), suggesting improved re-utilization of non-recyclable purines avoid hypoxanthine accumulation and reduce oxidative stress. Most intriguingly, we found that six unique substitutions in cetacean xanthine dehydrogenase(XDH), an enzyme that regulates the generation of the ROS precursor xanthine oxidase(XO) during ischemic/hypoxic conditions, show enhanced enzyme activity and thermal stability and diminished XO conversion activity. These functional adaptations are likely beneficial for cetaceans by reducing radical oxygen species production during diving. In summary, our findings offer insights into the molecular and functional evolution of purine metabolism genes in mammalian oxidative stress adaptations.

Chlorogenic Acid Metabolism:The Evolution and Roles in Plant Response to Abiotic Stress

During the evolution,plants acquired the ability to synthesize different phenylpropanoid compounds like chlorogenic acid(CGA),which plays vital roles in resistance mechanisms to abiotic stresses.These environmental factors,including heavy metal,cold,heat,ultraviolet(UV)light,drought,and salinity affect the plant physiological processes,resulting in massive losses of agriculture production.As plants evolve from green algae to bryophytes,ferns,gymnosperms and angiosperms,phenylpropanoids are produced and accumulated in different tissues,giving the plant the capacity to counteract the harmful effects of the adverse environments.Studies have been performed on the metabolic evolution of rosmarinic acid,flavonoids and lignin,showing that the biosynthesis of phenylpropanoids begins in green algae until the emersion of genes found in angiosperms;however,the evolution of the CGA pathway has not yet been reviewed.We hypothesize that CGA could also be synthesized from algae to angiosperms.In the present review,the evolutionary analysis of CGA pathway and the function of this compound in plant tolerance to abiotic stresses are summarized.Bioinformatics analyzes were carried out on CGA-related genes across 37 plant species and revealed that the metabolic pathway starts in algae and gradually increases until it becomes complete in angiosperms.The key genes exhibited different expression patterns in stress and plant tissues.Interestingly,some genes accumulated rapidly during evolution and were more sensitive to environmental stresses,while others appeared only later in angiosperms.Further studies are needed to better understand the evolution of the CGA metabolic pathway in plants under environmentally stressed conditions.

Stress field evolution law of mining environment reconstructing structure with change of filling height

For improving global stability of mining environment reconstructing structure,the stress field evolution law of the structure with the filling height change of low-grade backfill was studied by ADINA finite element analysis code.Three kinds of filling schemes were designed and calculated,in which the filling heights were 2,4,and 7 m,separately.The results show that there are some rules in the stress field with the increase of the filling height as follows:(1) the maximum value of tension stress of the roof decreases gradually,and stress conditions are improved gradually;(2) the tension stress status in the vertical pillar is transformed into the compressive stress status,and the carrying capacity is improved gradually;however,when the filling height is beyond 2.8 m,the carrying capacity of the vertical pillar grows very slowly,so,there is little significance to continue to fill the low-grade backfill;(3) the bottom pillar suffers the squeezing action from the vertical pillars at first and then the gravity action of the low-grade backfill,and the maximum value of tension stress of the bottom pillar firstly increases and then decreases.Considering the economic factor,security and other factors,the low-grade backfill has the most reasonable height(2.8 m) in the scope of all filling height.

Crustal Stress Evolution over the Past 700 Years in North China and Earthquake Occurrence

Fault interaction and earthquake occurrence have attracted much attention in seismological community during recent years. Many studies have shown that the rupture of one fault could encourage or discourage earthquake nucleation on a neighboring fault, depending on the relative geometry of the two faults and the earthquake rupture mechanisms. In this paper, we simulate the evolutionary process of cumulative Coulomb failure stress change （ CCFSC ） in North China since 1303, manifested by secular tectonic stress loading and occurrence of large earthquakes. Secular tectonic stress loading is averaged from crustal strain rates derived from GPS. Fault rupture parameters of historical earthquakes are estimated as follows： the earthquake rupture length and the amount of slip are derived based on their statistical relationships with the earthquake intensity distribution and magnitude, calibrated using parameters of instrumentally measured contemporary earthquakes. The earthquake rake angle is derived based on geologically determined fault orientational parameters and seismically estimated orientation of regional tectonic stresses. Assuming a layered visco-elastic medium, we calculate stress evolution resulting from secular tectonic loading and coseismic and postseismic deformation. On the eve of each large earthquake, the accumulated stress field is projected to the fault surface of that earthquake and the CCFSC is evaluated to assess the triggering effect of CCFSC. Forty-nine earthquakes with M≥6.5 have occurred in North China since 1303. Statistics shows that 39 out of the 48 subsequent events were triggered by positive CCFSC, yielding a triggering rate of 81.3%. If we use the accumulative stress field to evaluate the CCFSC for the M ≥ 5.0 earthquakes that occurred in North China since 1303, we find that 75.5% of those events were triggered. The triggering rate for the M ≥ 5.0 earthquakes after the 1976 Ninghe earthquake is up to 82.1%. The triggering rates can be higher if corrections are made for some aftershocks which were wrongly identified as occurring in stress shadow zones because of errors in parameter estimates of historical earthquakes. Our study shows a very high correlation between positive CCFSC and earthquake occurrences. Relatively high CCFSC in North China at present is concentrated around the Bohai Sea, the west segment of the Northern Qinling fault, the western end of the Zhangjiakou-Bohai Sea seismic zone, and the shiyuan basin, Shanxi graben, suggesting relatively higher earthquake potential in these areas.

4D-stress evolution of tight sandstone reservoir during horizontal wells injection and production: A case study of Yuan 284 block,Ordos Basin,NW China

To investigate the 4D stress change during injection and production in tight sandstone reservoirs, a multi-physical fields modeling method is proposed considering the reservoir heterogeneity, hydraulic fracture and complex injection-production system. The 4D stress evolution of tight sandstone reservoir in Yuan 284 block of Huaqing oilfield, Ordos Basin,during injection-production in horizontal well network is investigated by modeling coupled flow and geomechanics. Results show:(1) Induced by injection and production, the 3D stress increases near the injectors but decreases near the producers, and the horizontal stresses are distributed in obvious strips along their respective stress directions.(2) The horizontal stress difference is the highest at the horizontal wellbore beside injectors during injection and production, while it is the lowest in undeveloped zone between the injectors, and the orientation of maximum horizontal principal stress changes the most near the injectors, which is distributed radially.(3) The hydraulic fracture in re-fracturing well was observed to be asymmetrical in geometry and deflected as the stress changed. The results provide theoretical guidance for horizantal well network modification and re-fracturing optimization design in tight sandstone reservoir.

Flow stress and microstructure evolution of semi-continuous casting AZ70 Mg-alloy during hot compression deformation

To evaluate and predict flow stress and set up hot forging process of AZ70 magnesium alloy,hot compression tests of AZ70 magnesium alloy were carried out on Gleeble 1500D thermo-mechanics tester at 300-420℃and strain rates of 0.001-1 s- 1 with different compression degrees.It is indicated that temperature and strain rate are the main factor affecting the flow stress and microstructure.Stress increases but average grain size decreases with temperature decreasing and strain rate increasing.The stress model,constituted by introducing temperature-compensated strain rate,the Zener-Hollomon parameter,has a good fitness with the proof stress value under the experimental condition.The reciprocal of grain size at true strain of 1.0 has a linear relation with natural logarithm of Z parameter,and the correlation coefficient,R=0.95,is very significant by examination.The hot deformation activation energy Q of AZ70 alloy is 166.197 kJ/mol by calculation.