Mg-5.88 Zn-0.53 Cu-0.16 Zr(wt.%)alloy was solidified at 2-6 GPa using high-pressure solidification technology.The microstructure,strengthening mechanism and compressive properties at room temperature were studied usin...Mg-5.88 Zn-0.53 Cu-0.16 Zr(wt.%)alloy was solidified at 2-6 GPa using high-pressure solidification technology.The microstructure,strengthening mechanism and compressive properties at room temperature were studied using SEM and XRD.The results showed that the microstructure was refined and the secondary dendrite spacing changed from 35μm at atmospheric pressure to 10μm at 6 GPa gradually.Also,Mg(Zn,Cu)2 and Mg Zn Cu eutectic phases were distributed in the shape of network,while under high pressures the second phases(Mg(Zn,Cu)2 and Mg7 Zn3)were mainly granular or strip-like.The solid solubility of Zn and Cu in the matrix built up over increasing solidification pressure and reached 4.12%and 0.32%respectively at 6 GPa.The hardness value was HV 90 and the maximum compression resistance was 430 MPa.Therefore,the grain refinement strengthening,the second phase strengthening and the solid solution strengthening are the principal strengthening mechanisms.展开更多
This paper proves an index theorem of Toeplitz tuples on pseudoregular domains in Cn. Geometrically, the index of Toeplitz tupleT n is (-1) n time wrapping number of φ n around the origin. As one of the applications ...This paper proves an index theorem of Toeplitz tuples on pseudoregular domains in Cn. Geometrically, the index of Toeplitz tupleT n is (-1) n time wrapping number of φ n around the origin. As one of the applications of the index theorem, we completely characterize the automorphism groups of Toeplitz algebras on Poincaré domain. As another application, it is shown thatC*(Ω)?C*(Bn) for every Poincare domain Ω inC n (n≠2). It is also noticed thatC*(Ω)?C*(B 2) if and only if the Poincaré conjecture is true for ?Ω.展开更多
基金Projects(51675092,51775099)supported by the National Natural Science Foundation of ChinaProjects(E2018501030,E2018501033,E2018501032)supported by the Natural Science Foundation of Hebei Province,China.
文摘Mg-5.88 Zn-0.53 Cu-0.16 Zr(wt.%)alloy was solidified at 2-6 GPa using high-pressure solidification technology.The microstructure,strengthening mechanism and compressive properties at room temperature were studied using SEM and XRD.The results showed that the microstructure was refined and the secondary dendrite spacing changed from 35μm at atmospheric pressure to 10μm at 6 GPa gradually.Also,Mg(Zn,Cu)2 and Mg Zn Cu eutectic phases were distributed in the shape of network,while under high pressures the second phases(Mg(Zn,Cu)2 and Mg7 Zn3)were mainly granular or strip-like.The solid solubility of Zn and Cu in the matrix built up over increasing solidification pressure and reached 4.12%and 0.32%respectively at 6 GPa.The hardness value was HV 90 and the maximum compression resistance was 430 MPa.Therefore,the grain refinement strengthening,the second phase strengthening and the solid solution strengthening are the principal strengthening mechanisms.
文摘This paper proves an index theorem of Toeplitz tuples on pseudoregular domains in Cn. Geometrically, the index of Toeplitz tupleT n is (-1) n time wrapping number of φ n around the origin. As one of the applications of the index theorem, we completely characterize the automorphism groups of Toeplitz algebras on Poincaré domain. As another application, it is shown thatC*(Ω)?C*(Bn) for every Poincare domain Ω inC n (n≠2). It is also noticed thatC*(Ω)?C*(B 2) if and only if the Poincaré conjecture is true for ?Ω.
