The pure α-Ti samples were heated at an extremely high rate （～10^6 K/s） to the temperature of β phase zone followed by a rapidly quenching in an electro-pulsing treatment. After the treatment, micrometer-thick lamellar substructures were generated within the original equiaxed α-Ti coarse grains. Misorientations across adjacent lamellae are of a few degrees. The ultrafine lamellar substructures originated from a non-equilibrium α-β-α’ phase transformation during rapidly heating-quenching process with a short exposure time at high temperatures. Tensile strength was increased by about 100 MPa due to the formation of the ultrafine lamellar substructure while the same tensile plasticity （elongation-to-failure） was maintained relative to the original sample. The strengthening effect could be attributed to the effective blockage of dislocation motions by a high density of sub-boundaries.
Weisong ZHAO Wei ZHANG Jinyu GUO Boquan WANG Jingdong GUO Ke LU
The Monte Carlo simulation with the energetics described by the embedded atom method has been employed to mainly study physical behaviors of boron atoms during relaxation of the Ni3Al-x at.% B grain boundary.During relaxation of impure Ni3Al grain boundaries,we suggest that for different types of impure atoms(Mg,B,Cr and Zr atoms etc.),as the segregating species,they have the different behaviors,but as the inducing species,they have the same behaviors,i.e.they all induce Ni atoms to substitute Al atoms.Calculations show that at the equilibrium.when x(the B bulk concentration) increases from 0.1 to 0.9,the peak concentration of B increases,correspondently,the peak concentration of Ni maximizes but the valley concentration of Al minimizes,at x=0.5,The calculations also show the approximate saturation of Ni at the grain boundary at x=0.5.
Before clinical application of a new source, the dosimetric parameters of the source should be accu- rately determined. This work is dedicated to the Monte Carlo method to calculate dosimetric parameters as recommended by the American Association of Physicists in Medicine (AAPM) TG-43 guidelines for model ADVANTAGETM palladium-103 source and, through comparison with data from another published report for the same source, presents a suggested dataset for clinical applications. From these calcula- tions, tables are presented for the radial dose function and the anisotropy function of palladium-103 brachytherapy source. The dose rate constants are found to be 0.671 (cGyh-1U-1) in liquid water and 0.673 (cGyh-1U-1) in Solid WaterTM. And the anisotropy constants in liquid water and Solid WaterTM are found to be 0.864 and 0.865 respectively. Comparison with the previous study shows that our results of dosimetric parameters are in good agreement with those measured and calculated by Meigooni et al. (2006) both in Water and Solid WaterTM.
WANG JianHua LIU Wei XU XunJiang GU JiaHui CAI Jun HUA ZhengDong XU JiaQiang
