Unveiling the mechanical response and accommodation mechanism of pre-rolled AZ31 magnesium alloy under high-speed impact loading

Split Hopkinson pressure bar(SHPB)tests were conducted on pre-rolled AZ31 magnesium alloy at 150–350℃ with strain rates of 2150s-1,3430s^(-1) and 4160s-1.The mechanical response,microstructural evolution and accommodation mechanism of the pre-rolled AZ31 magnesium alloy under high-speed impact loading were investigated.The twin and shear band are prevailing at low temperature,and the coexistence of twins and recrystallized grains is the dominant microstructure at medium temperature,while at high temperature,dynamic recrystallization(DRX)is almost complete.The increment of temperature reduces the critical condition difference between twinning and DRX,and the recrystallized temperature decreases with increasing strain rate.The mechanical response is related to the competition among the shear band strengthen,the twin strengthen and the fine grain strengthen and determined by the prevailing grain structure.The fine grain strengthen could compensate soften caused by the temperature increase and the reduction of twin and shear band.During high-speed deformation,different twin variants,introduced by pre-rolling,induce different deformation mechanism to accommodate plastic deformation and are in favor for non-basal slip.At low temperature,the high-speed deformation is achieved by twinning,dislocation slip and the following deformation shear band at different deformation stages.At high temperature,the high-speed deformation is realized by twinning and dislocation slip of early deformation stage,transition shear band of medium deformation stage and DRX of final deformation stage.

Effects of Leaf Extract of Phyllanthus reticulatus from Guangxi on Human Gastric Cancer SGC-7901 Cells in vitro

[Objectives]To observe the effect of drug-containing serum from different extracts of Phyllanthus reticulatus leaf on the proliferation of human gastric cancer SGC-7901 cells and the effect of in vivo on the life extension rate of mice with H22 ascites tumor,and to investigate the effects of chemical components such as Corilagin,ethyl gallate,ethyl brevifolincarboxylate,and gallic acid on the proliferation of human gastric cancer SGC-7901 cells.[Methods]MTT method was used to observe the inhibitory effect of drug-containing serum of different extracts of P.reticulatus leaf on human gastric cancer SGC-7901 cells in vitro to determine its active site.The active site was used as the research object to establish a Kunming mouse ascites tumor model,to investigate the effect on the life extension rate of mice with H22 ascites tumor,to further separate the monomer components from the effective fraction and investigate its effect on human gastric cancer SGC-7901 cells.[Results]Compared with the 10%blank serum control group,10%drug-containing serum of ethyl acetate and n-butanol in P.reticulatus leaf had significant inhibitory effect on the proliferation of human gastric cancer SGC-7901 cells,and the inhibition rate was 34.99%and 28.68%,respectively(P<0.05).Compared with the blank group,the survival time of the high dose group of ethyl acetate in P.reticulatus leaf was significant(P<0.05).Gallic acid,Corilagin,and Brevifolincarboxylic acid ethyl ester had a significant inhibitory effect on the proliferation of human gastric cancer SGC-7901 cells,with IC 50 of 26.52,70.45,and 158.86μg/mL,respectively.Ethyl gallate had no inhibitory effect on the proliferation of human gastric cancer SGC-7901 cells,and its IC 50 was 251.96μg/mL.[Conclusions]The drug-containing serum of ethyl acetate and n-butanol extract of P.reticulatus can inhibit the proliferation of human gastric cancer SGC-7901 cells.Ethyl acetate of P.reticulatus leaves can increase the life extension rate of mice with H22 ascites tumor.Gallic acid,Corilagin,and Brevifolincarboxylic acid ethyl ester isolated from its active site are the material basis for inhibiting the proliferation of human gastric cancer SGC-7901 cells.

Nucleation and growth of L1_(2)-Al_(3)RE particles in aluminum alloys:A first-principles study

The internal mechanisms of nucleation and growth of L1_(2)-AI_(3)RE(RE=Sc,Y,La-Lu) second phases in Al alloys were investigated by combining first-principles calculations with quasi-harmonic approximation(QHA).The calculated results show that the diffusion rate D_s and chemical potential AG_V increase with the increase of temperature.With the increase of atomic number,the D_s and the strain energy ΔE_(CS)increase firstly from Sc to La,and then decreases,while the calculated interface energy γ_(α/β) and ΔG_V show opposite tendency.Based on above calculated results,the critical nucleation radius R*and coarsening rate K_(LSW) are obtained from the classical nucleation theory(CNT) and LSW model of the Ostwald ripening of particles,respectively.With the increase of atomic number,the R*increases firstly,and then decreases for all planes at finite temperatures.Whereas the K_(LSW) shows opposite variation to the R^(*).From this point of view,it is reasonably speculated that Y and later RE elements can replace the expensive Sc for heat-resistance Al alloys.The solubility c_(∞) of particles is usually very small at low temperature,and there is obvious solubility only when the temperature reaches 600 K.The surface energies E_(sur) of AI_(3)RE compounds and Al solid solution are respectively larger and smaller than that of pure Al,respectively,except for the surface(001) and(110) of Al_(3)La.For all planes,with the increase of atomic number of RE,E_(sur) decreases firstly from Sc to La,and then increases linearly to Lu.These results are helpful for designing high performance heat-resistance Al alloys.