Temperature-jump tensile tests to induce optimized TRIP/TWIP effect in a metastable austenitic stainless steel

In the present work,plastic deformation mechanisms were initially tailored by adjusting the deformation temperature in the range of 0 to 200℃ in AISI 304L austenitic stainless steel,aiming to optimize the strength-ductility synergy.It was shown that the combined twinning-induced plasticity(TWIP)/transformation-induced plasticity(TRIP)effects and a wider strain range for the TRIP effect up to higher strains by adjusting the deformation temperature are good strategies to improve the strength-ductility synergy of this metastable stainless steel.In this regard,by consideration of the observed temperature-dependency of plastic deformation,the controlled sequence of TWIP and TRIP effects for archiving superior strength-ductility trade-off was intended by the pre-designed temperature jump tensile tests.Accordingly,the optimum tensile toughness of 846 MJ/m^(3) and total elongation to 133% were obtained by this strategy via exploiting the advantages of the TWIP effect at 100℃ and the TRIP effect at 25℃ at the later stages of the straining.Consequently,a deformation-temperature-transformation(DTT)diagram was developed for this metastable alloy.Moreover,based on work-hardening analysis,it was found that the main phenomenon constraining further improvement in the ductility and strengthening was the yielding of the deformation-induced α′-martensite.

Metastable face-centered cubic ruthenium-based binary alloy for efficient alkaline hydrogen oxidation electrocatalysis

Metastable nanostructured electrocatalyst with a completely different surface environment compared to conventional phase-based electrocatalyst often shows distinctive catalytic property.Although Ru-based electrocatalysts have been widely investigated toward hydrogen oxidation reaction(HOR)under alkaline electrolytes,these studies are mostly limited to conventional hexagonal-close-packed(hcp)phase,mainly arising from the lack of sufficient synthesis strategies.In this study,we report the precise synthesis of metastable binary RuW alloy with face-centered-cubic(fcc)phase.We find that the introduction of W can serve as fcc phase seeds and reduce the formation energy of metastable fcc-RuW alloy.Impressively,fcc-RuW exhibits remarkable alkaline HOR performance and stability with the activity of 0.67 mA cm_(Ru)^(-2)which is almost five and three times higher than that of hcp-Ru and commercial Pt/C,respectively,which is attributed to the optimized binding strength of adsorbed hydroxide intermediate derived from tailored electronic structure through W doping and phase engineering.Moreover,this strategy can also be applied to synthesize other metastable fcc-RuCr and fcc-RuMo alloys with enhanced HOR performances.

Lifetime measurement of the 3d^(9) ^(2)D_(3/2) metastable level in Mo^(15+)at an electron beam ion trap

An experimental measurement of the lifetime of 3d^(9) ^(2)D_(3/2) metastable level in Mo^(15+)is reported in this work.The Mo^(15+)ions are produced and trapped in an electron beam ion trap with a magnetic field of 0.65 T.The decay photons emitted from 3d^(9) ^(2)D_(3/2) level are subsequently recorded via a cooled photomultiplier tube.Through meticulous scrutiny of potential systematic uncertainties affecting the measurement outcomes,we have determined the lifetime of Mo^(15+)3d^(9)2D_(3/2)metastable level to be 2.83(22)ms.The experimental result provides a clear distinguishment from existing calculations based on various theoretical approaches.

Double Differential Cross-Section for the Ionization of Hydrogenic 2S Metastable State

Double differential cross-sections of first Born estimation for ionization of hydrogenic 2S state by electrons are assessed for various kinematics situations in the asymmetric coplanar geometry. A final state wave function of multiple scattering theory is followed in this study. The present outcomes are compared with those of hydrogenic ground state, 2P state and ground state experimental results. Obtained findings show a good qualitative agreement with existing results.

miR-132 inhibits colorectal cancer invasion and metastasis via directly targeting ZEB2

AIM:To investigate the biological role and underlying mechanism of miR-132 in colorectal cancer(CRC)progression and invasion.METHODS:Quantitative RT-PCR analysis was used to examine the expression levels of miR-132 in five CRC cell lines(SW480,SW620,HCT116,HT29 and LoVo)and a normal colonic cell line NCM460,as well as in tumor tissues with or without metastases.The KaplanMeier method was used to analyze the prognostic significance of miR-132 in CRC patients.The biological effects of miR-132 were assessed in CRC cell lines using the transwell assay.Quantitative RT-PCR and western blot analyses were employed to evaluate the expression of miR-132 targets.The regulation of ZEB2 by miR-132was confirmed using the luciferase activity assay.RESULTS:miR-132 was significantly down-regulated in the CRC cell lines compared with the normal colonic cell line(P<0.05),as well as in the CRC tissues withdistant metastases compared with the tissues without metastases(10.52±4.69 vs 23.11±7.84)(P<0.001).Down-regulation of miR-132 was associated with tumor size(P=0.016),distant metastasis(P=0.002),and TNM stage(P=0.020)in CRC patients.Kaplan-Meier survival curve analysis indicated that patients with low expression of miR-132 tended to have worse diseasefree survival than patients with high expression of miR-132(P<0.001).Moreover,ectopic expression of miR-132 markedly inhibited cell invasion(P<0.05)and the epithelial-mesenchymal transition(EMT)in CRC cell lines.Further investigation revealed ZEB2,an EMT regulator,was a downstream target of miR-132.CONCLUSION:Our study indicated that miR-132 plays an important role in the invasion and metastasis of CRC.

Study on the metastable state of dilution of spectinomycin

采用诱导期法和直接法研究了大观霉素溶析结晶的介稳态.新相形成由多核机理控制.由多核机理得到两个操作温度下溶析结晶的介稳区.实验考察了丙酮浓度和温度对溶析结晶介稳态的影响.随着丙酮浓度的增大或温度的降低,诱导期延长.介稳区宽度随溶解度的减小而变宽.大观霉素初级成核的过饱和度水平较高,属于第Ⅰ类物系.根据经典成核理论估算了大观霉素成核参数.这些实验结果对大观霉素溶析结晶工业生产的控制具有重要意义.

EXPLOITATION AND APPLICATIONS OF METASTABLE AUSTENITE MATRIX WEAR ALLOYS

Fe based cast alloys with double phases structure of m etastable austenite m atrix an d eutecticcarbide M7 C3 were provided with the excellent properties of high abrasion resistance andhigher i m pact toughness . An i m portant reason of high abrasion resistance is hard ness violentincreasing on the m atrix surface because of w ear easily induced m artensite transfor m ation . The exploitation and applications of m etastable austenite m atrix wear alloys of Fe C Cr Nisyste m and Fe C Cr Mn system were described in this paper . The excellent properties of thesealloys w ill be sufficiently indicated by authors’exa m ples . To exploit a class of these alloyswith high abrasion resistance and various im pact toughness for m eeting the requirem ent of dif ferent environ ment , the proble m of the structure design of metastable austenite m atrix wearalloy w as also described in this paper .

Stable and metastable phase equilibria in binary Mg-Gd system: A comprehensive understanding aided by CALPHAD modeling

In this paper,a comprehensive understanding of stable and metastable phase equilibria in binary Mg-Gd system was conducted with an aid of the CALculation of PHAse Diagram(CALPHAD)modeling.Firstly,thermodynamic descriptions of all the stable phases in the Mg-Gd system were re-assessed by considering all the experimental data in the literature.The discrepancy between the phase equilibria and thermochemical properties existing in the previous assessments was eliminated,and the better agreement with the experimental data was achieved in the present assessment.Secondly,the Gibbs energies for metastable β"-Mg3Gd and β"-Mg7Gd were constructed based on the first-principles and CALPHAD computed results as well as their correlation,and then incorporated into the CALPHAD descriptions.The model-predicted solvuses of(Mg)in equilibrium with the metastable β"-Mg7Gd and β'-Mg7Gd compounds showed very good agreement with the limited experimental data.Finally,the presently obtained thermodynamic descriptions of both stable and metastable phases in the binary Mg-Gd system were further validated by realizing the quantitative Scheil-Gulliver solidification simulations of 5 as-cast Mg-Gd alloys,and the successful prediction of the precipitation sequences in Mg-15Gd and Mg-12Gd alloys during the aging process.

Microstructure Evolution in a Rapidly Solidified Cu85Fe15 Alloy Undercooled into the Metastable Miscibility Gap

A model has been developed to describe the microstructure evolution in the atomized droplets of Cu-Fe alloy during cooling through the metastable miscibility gap. Calculations have been performed for Cu85Fe15 alloy to investigate the process of liquid-liquid phase transformation. The numerical results indicate that the minority phase droplets are nucleated in a temperature region around the peak of the supersaturation. The average radius of the Fe-rlch droplets decreases and the number density of the minority phase droplets increases with decreasing the atomized droplet size. The simulated results were compared with the experimental ones. The kinetic process of the liquid-liquid phase transformation was discussed in detail.

Metastable Equilibrium in Quaternary System Li_2SO_4+K_2SO_4+Li_2CO_3+K_2CO_3+H_2O at 288 K

Metastable equilibrium solubilities and densities of the Li2SO4 ＋ K2SO4 ＋ Li2CO3 ＋ K2CO3 ＋ H2O system at 288 K were determined experimentally by using the isothermal evaporation method. According to the experimental data, the metastable equilibrium solubility phase diagram was constructed. In the phase diagram, there are three invariant points, seven univariant curves, and five fields of crystallization： Li2SO4· H2O2,K2SO4, Li2CO3, K2CO3 · 3/ 2H2O and K2SO4· Li2SO4. The double salt K2SO4 · Li2SO4 was found in the metastable equilibria. Lithium carbonate（ Li2CO3 ） has the smallest solubility in the quaternary system.

Non-equilibrium microstructure and the metastable phase of Al-9.6wt%Mg Alloy solidification under high pressure

The non-equilibrium microstructure and a new metastable phase of Al-9.6wt%Mg alloy solidified at 6 GPa were studied by optical microscope,differential scanning calorimetry,X-ray diffraction and transmission electron microscope.The results showed that dendrite microstructure was refined,and the solid solubility of Mg in α-Al phase increased greatly.Correspondingly,the lattice parameter of α-Al phase increased.Al3Mg2 phases disappeared under high pressure solidification.In particular,a metastable phase with small size(20 nm or so) was produced in the alloy,its melting temperature range was 464～518.2 ℃,which was higher than that of Al3Mg2 phase(453～465 ℃) under normal pressure.These metastable phases located in the interdendritic position.It was the first time that the metastable phase was found in Al-Mg alloy at a high pressure of 6 GPa.The formation mechanism of the metastable phases was discussed.

Determination of the metastable zone and induction time of thiourea for cooling crystallization

The solubility,metastable zone width(MSZW),and induction time of thiourea for cooling crystallization were experimentally determined in the temperature range of 283-323 K.The solubility data could be well described by the Apelblat equation model as lnx=-99.55+1071.66/T+16.27 lnT.The determinations of the effects of various stirring and cooling rates indicated that the MSZW increased with increasing and decreasing cooling and stirring rates,respectively.Furthermore,the induction times at various temperatures and supersaturation ratios were also measured.The results indicated that homogeneous nucleation could occur at high supersaturation,whereas heterogeneous nucleation was more likely to occur at low supersaturation.Based on the classical nucleation theory and induction period data,the calculated solid-liquid interfacial tensions of thiourea in deionized water at 302.46 and 312.58 K were 2.86 and 2.94 mJ·m^(-2),respectively.

Solid-liquid Metastable Equilibria in Quaternary System Li_2SO_4+Li_2CO_3+Li_2B_4O_7+H_2O at 288 K

Metastable equilibrium solubilities and densities of quaternary system Li2SO4＋Li2CO3＋ Li2B4O7＋H2O at 288 K were determined by isothermal evaporation method. According to the experimental data, the metastable equilibrium phase diagram was plotted. The metastable phase diagram had one invariant point F, three double saturated liquid curves ElF, E2F and E3F, and three crystallization fields corresponding to Li2SO4·H2O, Li2CO3 and LiBO2·8H2O. It was found that lithium sulphate（Li2SO4） had the highest concentration and strong salting-out effects on the other salts. There were no solid solutions or double salts formed in the quaternary system at 288 K.

The Role of Metastable Atoms in a Homogeneous Atmospheric Pressure Barrier Discharge in Helium

A one-dimensional fluid model for homogeneous atmospheric pressure barrier discharges in helium is presented by considering elementary processes of excitation and ionization including a metastable atom effect. Using this model we investigate the behaviours of the helium metastable atoms in discharges as well as their influence on the discharge characteristics. It is shown that the metastable atoms with a relatively high concentration during the discharge are mainly produced in the active phase of the discharge and dissolved in the off phase. It is also found that the metastable atom collisions can not only provide seed electrons for discharges but also influence the concentration of ions. A reduction of matestable atom density results in a drop in the charged particle densities and causes a qualitative change in the discharge patterns.

Metastable state of gas hydrate during decomposition: A novel phenomenon

Natural gas hydrates are solid compounds with cage-like structures formed by gas and water.An intriguing phenomenon that gas hydrates can dissociate at a low rate below the ice freezing point has been viewed as the metastability of hydrate.The mechanisms of hydrate metastability have been widely studied,and many mechanisms were proposed involving the self-preservation effect,supercooled water-gas-hydrate metastable equilibrium,and supersaturated liquid-gas-hydrate system etc.The metastable state of hydrate could be of crucial significance in the kinetics of hydrate formation and decomposition,heat and mass transfer during gas production processes,and the application of hydrate-based technique involving desalination,energy storage and transportation,and gas separation and sequestration.Few researches have systematically considered this phenomenon,and its mechanism remains unclear.In this work,various mechanisms and hypothesis explaining the metastable state of gas hydrates were introduced and discussed.Further studies are still required to reveal the intrinsic nature of this metastable state of gas hydrate,and this work could give some implications on the existing theory and current status of relevant efforts.

A new synthetic route to MgO–MgAl2O4–ZrO2 highly dispersed composite material through formation of Mg5Al2.4Zr1.7O12 metastable phase: synthesis and physical properties

Mg_5Al_(2.4)Zr_(1.7)O_(12) metastable phase was successfully synthesized from analytical-grade Mg O,α-Al_2O_3,MgAl_2O_4,and ZrO_2 under an N_2 atmosphere.The sintering temperature was varied from 1650 to 1780°C,and the highest amount of Mg_5Al_(2.4)Zr_(1.7)O_(12) appeared in the composite material when the sintering temperature was 1760°C.According to our research of the formation mechanism of Mg_5Al_(2.4)Zr_(1.7)O_(12),the formation and growth of MgAl_2O_4 dominated when the temperature was not higher than 1650°C.When the temperature was higher than 1650°C,MgO and ZrO_2 tended to diffuse into MgAl_2O_4 and the Mg_5Al_(2.4)Zr_(1.7)O_(12) solid solution was formed.When the temperature reached 1760°C,the formation of Mg_5Al_(2.4)Zr_(1.7)O_(12) was completed.The effect of Mg Al_2O_4 spinel crystals was also studied,and their introduction into the composite material promoted the formation and growth of Mg_5Al_(2.4)Zr_(1.7)O_(12).A highly dispersed MgO–Mg Al_2O_4–ZrO_2 composite material was prepared through the decomposition of the Mg_5Al_(2.4)Zr_(1.7)O_(12) metastable phase.The as-prepared composite material showed improved overall physical properties because of the good dispersion of MgO,MgAl_2O_4,and ZrO_2 phases.

Metastable phase separation and rapid solidification of undercooled Co_(40)Fe_(40)Cu_(20) alloy

The metastable liquid phase separation and rapid solidification behaviors of Co_（40） Fe_（40） Cu_（20） alloy were investigated by using differential thermal analysis（DTA） in combination with glass fluxing and electromagnetic levitation（EML） techniques. The critical liquid phase separation undercooling for this alloy was determined by DTA to be 174 K. Macrosegregation morphologies are formed in the bulk samples processed by both DTA and EML. It is revealed that undercooling level, cooling rate, convection, and surface tension difference between the two separated phases play a dominant role in the coalescence and segregation of the separated phases. The growth velocity of the（Fe,Co） dendrite has been measured as a function of undercooling up to 275 K. The temperature rise resulting from recalescence increases linearly with the increase of undercooling because of the enhancement of recalescence. The slope change of the recalescence temperature rise versus undercooling at the critical undercooling also implies the occurrence of liquid demixing.

METASTABLE STATE TRANSFOR MATIONS OF Al_3Ti BASE ALLOYS DURING MECHANICAL MILLING AND SUBSEQUENT ANNEALING

Developing multi phase alloy is an effective approach for the strengthening and toughening of the L1 2 Al 3Ti alloy. A Nb modified Al 3Ti base alloy which has a L1 2 matrix and the precipitated second phase has been developed. Since the effect of second phase is strongly influenced by its size and distribution, high energy ball milling was employed to fabricate the alloy in comparison with the conventional casting process. It was found that structure evolution during mechanical milling is different for DO 22 , L1 2 and L1 2+DO 22 two phase alloys. The DO 22 Al 3Ti transformed only to a FCC structure even after long time milling. The ordering of L1 2 Al 67 Ti 25 Mn 8 decreased quickly and changed into a FCC structure after short time milling, subsequent milling led to the amorphous transition. The DO 22 phase in Al 3Ti Mn Nb alloys dissolved into the L1 2 matrix quickly in the early stage of milling and the matrix changed into a FCC supersaturated solid solution after 10 h milling, further milling led to the amorphous transition. Reordering of the metastable structures occurred during the annealing process. The consolidated materials consisting of fine equiaxed grains with dispersed particles exhibited remarkable improvement of strength and promising ductility.

PREPARATION OF ULTRAFINE POWDER OF Fe AND ZrO_2 WITH METASTABLE PHASES BY HIGH POWER LASER BEAMS

The radiation of material surface by high intensity laser beams is used to produce the uhrafine powder of pure Fe and ZrO_2.The morphology,size and phases of the powder were examined by X-ray diffraetometer,scanning electron microscopy as well as transmission electron microscopy.In pure Fe a considerable quantity of γ-phase was found in the powder.In ZrO_2 powder,instead of stable phase,two metastable phases appeared.

Potential energy curves and analytical potential energy functions of the metastable states of B2^＋＋

The multi-reference configuration interaction method and aug-cc-pvqz （AVQZ） have been used to calculate potential energy curves （PECs） of the singlet and triplet states of the riu and rig symmetry of B2＋＋. All of the four states （^l∏u, ^1∏g, ^3∏u and ^3∏g） are found to be metastable states, though the potential well of ^3∏u symmetry is very shallow. Based on the PECs, the analytical potential energy functions （APEFs） of these states have been fitted using the least square fitting method and two models of function. The spectroscopic parameters of each state are also calculated, and are compared with other investigations in the literature. The credibility and veracity of the two functions are evaluated. Some ideas to improve the fitting accuracy are presented. Also the vibrational levels for each state are predicted by solving the SchrSdinger equation of nuclear motion.