通过Gleeble-1500热模拟单轴压缩试验，研究了一种含1.79% Al （质量分数）的以Al替代Si微合金化高强度钢在温度为900-1100℃、应变速率为0.01-30 s^-1条件下的热变形行为.建立了考虑应变量对材料常数影响的双曲正弦本构方程，利用建立的本构方程预测的应力-应变曲线与实验值吻合良好，表明建立的本构方程可以对实验钢的流变应力给出相对准确的预测.建立了实验钢的加工图，根据加工图分析确定了实验钢的动态再结晶区为1000-1100℃和0.01-1 s^-1.组织观察表明在动态再结晶区实验钢发生了动态再结晶，而失稳区对应的组织出现了变形集中带或“项链”组织.最后将建立的本构方程和加工图联合运用，为更全面地研究实验钢在不同变形条件下的热变形行为提供了方法.
Based on the Thermo-Calc thermodynamic software,the type of equilibrium precipitated carbides and their contents in high Mo Nb-microalloyed H13steel(NMH13steel)were calculated.The composition,morphology,and distribution of carbides after spheroidal annealing of two forged experimental steels were comparatively examined by means of optical microscopy(OM),scanning electron microscopy(SEM),electron dispersive spectroscopy(EDS)and transmission electron microscopy(TEM).VC,M23C6 and M6C are identified in H13 steel after spheroidizing annealing,while(V,Nb)C,M23C6,M2C and M6C are observed in NMH13 steel.Moreover,it is found that the addition of Nb significantly enhances the stability of MC phase and the high Mo content accelerates the precipitation of small rod-shape M2C phase in NMH13 steel.The amount of the fine carbides in NMH13 steel obviously increased with M2C and M6C precipitated from the ferrite phase,which is in accordance with the results of thermodynamic calculations.
Zn0.99Cu0.01O films were studied experimentally and theoretically.The films were prepared by pulsed-laser deposi tion on Pt(111)/Ti/SiO2/Si substrates under various oxygen pressures to investigate the growth-dependence of the ferromag netic properties.The structural,magnetic,and optical properties were studied,and it was found that all the samples possess a typical wurtzite structure,and that the films exhibit room-temperature ferromagnetism.The sample deposited at 600℃and an oxygen pressure of 10 Pa showed a large saturation magnetization of 0.83μB/Cu.The enhanced ferromagnetism in the(Cu,Li)-codoped ZnO is attributable to the existence of Zn vacancies(VZn),as shown by first-principles calcu lations.The photoluminescence analysis demonstrated the existence of V Zn in both Zn0.99Cu0.01O and(Cu,Li)-codoped ZnO thin films,and this plays an important role in the increase of ferromagnetism,according to the results of first-principles calculations.
The thermodynamic optimization of the Sn-Y and Mg-Sn-Y systems was critically carried out by means of the CALPHAD(CALculation of PHAse Diagram) technique. In the Sn-Y system, the solution phases(liquid, bcc, bct and hcp) were described by the substitutional solution model. The compound Sn3Y5, which has a homogeneity range, was treated as the formula(Sn, Y)3(Sn, Y)2Y3 by a three-sublattice model in accordance with the site occupancies. In the Mg-Sn-Y system, the liquid phase was treated as the formula(Mg, Sn, Y, Mg2Sn) using an associated solution model, and bcc, bct and hcp were treated as the formula(Mg, Sn, Y). The compound Sn3Y5 was treated as the formula(Sn, Y, Mg)3(Sn, Y, Mg)2Y3. The ternary compound MgSnY was treated as stoichiometric compound. A set of self-consistent thermodynamic parameters of the Mg-Sn-Y system was obtained. The projection of the liquidus surfaces and the reaction scheme of the Mg-Sn-Y system were predicted.
