The viewpoints aboutthe formation mechanism of bainite are described asfollowing aspects: ①Ultra finestructureof bainitein ferrous and nonferrousalloysis discovered by scanningtunneling microscopy (STM) .②STMstudi...The viewpoints aboutthe formation mechanism of bainite are described asfollowing aspects: ①Ultra finestructureof bainitein ferrous and nonferrousalloysis discovered by scanningtunneling microscopy (STM) .②STMstudies discoveredthatthesurface relief of bainiteissubstantiallycomposed of groupsofsmallrelieves which correspond of ultra fineunits,theirsurfacereliefistent shaped.③The frequency and mobility of 3 dimensionalsuperledgesinferrousand nonferrousareproved by TEMand STM.④Thebainitecarbide nucleateinthe ∪ sideof α/γinterfaceand grow toward austenite,thegrowth of carbide and ferrite arecom petitive.⑤STMstudies on surface relief of grain boundary allotriomorph ( GBA) andWidmansttten ferrite( WF) . They aretent shaped.⑥Theformation of bainiteisthroughsympathetic nucleation ledgewisegrowth mechanism .And both processesarecompetitive.⑦3 dimensional morphology of upper bainitetransformscontinuously to lower bainite, and noabruptlychange.展开更多
Based on pair potential, the Bragg Williams (B-W) model is modified to takeinto account the effect of the lattice parameter on theoretical order-disorder transformationanalysis. The main purpose of this work is to und...Based on pair potential, the Bragg Williams (B-W) model is modified to takeinto account the effect of the lattice parameter on theoretical order-disorder transformationanalysis. The main purpose of this work is to understand the basic aspects of this effect andrelated reasonable model on order-disorder transformation. In the present approach, theconfiguration free energy is chosen as function of the lattice parameter and the long-range order.This energy is calculated through Taylor's expansion, starting from the disordered state. It wasfound that the configuration free energy has been strongly modified when the lattice parameter istaken into account. It was also found only one type of order-disorder transformation exists in ABalloy and three kinds of order-disorder transformations for non-equiatomic alloy system such as A_3Balloy. This result is in agreement with experiments.展开更多
The Mg-A1 hydrogen storage alloy was suc- cessfully prepared by combustion synthesis （CS） method. The formation of alloy phases during the CS process was studied using X-ray diffraction （XRD）, scanning electron mi...The Mg-A1 hydrogen storage alloy was suc- cessfully prepared by combustion synthesis （CS） method. The formation of alloy phases during the CS process was studied using X-ray diffraction （XRD）, scanning electron microscope （SEM）, and differential scanning calorimetry （DSC）. When the time increases from 0, 0.5, 1.0 to 2.0 h at 733 K, the products are Mg and A1; Mg2A13, Mg and A1; Mgl7All2, Mg2A13; and Mg; and eventually only MgI7A112, respectively. Combined with three peaks in the DSC traces, it is concluded that the formation of MglyAll2 during the CS includes three processes, namely, the formation of MgzA13 first; then the unsaturated solid solution, MglvAla2; and finally the complete MglvA112 alloy. The formation of MgzA13 prior to MglvA112 in this work is different from those prepared by mechanical alloying. This is thought to be related to the instant high temperature during the ther- mal explosion of CS.展开更多
文摘The viewpoints aboutthe formation mechanism of bainite are described asfollowing aspects: ①Ultra finestructureof bainitein ferrous and nonferrousalloysis discovered by scanningtunneling microscopy (STM) .②STMstudies discoveredthatthesurface relief of bainiteissubstantiallycomposed of groupsofsmallrelieves which correspond of ultra fineunits,theirsurfacereliefistent shaped.③The frequency and mobility of 3 dimensionalsuperledgesinferrousand nonferrousareproved by TEMand STM.④Thebainitecarbide nucleateinthe ∪ sideof α/γinterfaceand grow toward austenite,thegrowth of carbide and ferrite arecom petitive.⑤STMstudies on surface relief of grain boundary allotriomorph ( GBA) andWidmansttten ferrite( WF) . They aretent shaped.⑥Theformation of bainiteisthroughsympathetic nucleation ledgewisegrowth mechanism .And both processesarecompetitive.⑦3 dimensional morphology of upper bainitetransformscontinuously to lower bainite, and noabruptlychange.
基金This work was financially supported by the National Natural Science Foundation of China under contract No. 59895151-01.
文摘Based on pair potential, the Bragg Williams (B-W) model is modified to takeinto account the effect of the lattice parameter on theoretical order-disorder transformationanalysis. The main purpose of this work is to understand the basic aspects of this effect andrelated reasonable model on order-disorder transformation. In the present approach, theconfiguration free energy is chosen as function of the lattice parameter and the long-range order.This energy is calculated through Taylor's expansion, starting from the disordered state. It wasfound that the configuration free energy has been strongly modified when the lattice parameter istaken into account. It was also found only one type of order-disorder transformation exists in ABalloy and three kinds of order-disorder transformations for non-equiatomic alloy system such as A_3Balloy. This result is in agreement with experiments.
基金financially supported by the National Natural Science Foundation of China(Nos.51071085 and 51171079)Specialized Research Fund for the Doctoral Program of High Education(No.20093221110008)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘The Mg-A1 hydrogen storage alloy was suc- cessfully prepared by combustion synthesis （CS） method. The formation of alloy phases during the CS process was studied using X-ray diffraction （XRD）, scanning electron microscope （SEM）, and differential scanning calorimetry （DSC）. When the time increases from 0, 0.5, 1.0 to 2.0 h at 733 K, the products are Mg and A1; Mg2A13, Mg and A1; Mgl7All2, Mg2A13; and Mg; and eventually only MgI7A112, respectively. Combined with three peaks in the DSC traces, it is concluded that the formation of MglyAll2 during the CS includes three processes, namely, the formation of MgzA13 first; then the unsaturated solid solution, MglvAla2; and finally the complete MglvA112 alloy. The formation of MgzA13 prior to MglvA112 in this work is different from those prepared by mechanical alloying. This is thought to be related to the instant high temperature during the ther- mal explosion of CS.
