DETERMINATION OF SPACE GROUP OF PrCo_(12)B_6 COMPOUND BY CONVERGENT BEAM ELECTRON DIFFRACTION

The space group of PrCo_(12)B_6,compound has been determined using the convergent beam elec-tron diffraction method.The space group is found to be R3m.     

DYNAMIC SEGREGATION OF SULPHUR IN CAST IRON

The segregation of sulphur at iron/graphite interfaces in both grey and nodular iron was in-vestigated with AES.Sulphur was found to nonequilibratorily segregate at the interfaces ingrey iron,but not in nodular iron.Such different behaviors of segregation,which will exagger-ate the difference of grey and nodular iron in sulphur content at iron/graphite interfaces,might be derived from the difference of solidification process between the two irons.     

SHORT-RANGE ORDER STRUCTURES OF Fe-Ge AMORPHOUS THIN FILMS

The short-range order structures of Fe_xGe_(1-x) amorphous thin films,(x=8.7,19.1 and28.5%)have been studied by means of X-ray absorption spectrum.The nearest neighborsaround a Ge or an Fe atom are constituted by two coordinate sub-shells with a very short dis-tance,In two films with lower Fe content,structural parameters of the nearest neighborsaround a Ge atom are very near to that in amorphous germanium,and the positions of Fe at-oms are randomly substitutional.But when x=28.5%,some great changes occur on theshort-range order structure of a-Fe_xGe_(1-x) film:its structure deviates from continuous ran-dora network and tends toward dense random packing of atoms.Meanwhile,there is a strong-er interaction between near neighboring Fe-Ge atoms in a-Fe_xGe_(1-x) films.     

LIQUIDUS OF SYSTEM Ag-Cu-Ge

The diagram of Ag-Cu-Ge system was constructed from the investigation of 13 internal sec-tions by DTA heating as well as cooling curves in an atomsphere of dry N_2 . The phase dia-gram is subdivided into two pseudo-ternary systems shown as Ag-Cu-Cu_3Ge andAg-Cu_3Ge-Ge. Both systems belong to simple eutectic type. The ternary eutectic points liein." E_1, Ag(22.0)-Cu(58.8)-Ge(19.2), 632℃ and E_2 , Ag(44.3)-Cu(29.5)-Ge(26.2), 533℃.The three side binary systems were redetermined.     

CALCULATION OF NaCl-BaCl_2-SrCl_2 PHASE DIAGRAM

The mathematical formulas are given for calculating the partial molar thermodynamic proper-ties in a ternary system from its three corresponding binary systems based on the new ternarysymmetric model presented by the authors in the foregoing paper.Applying this model toNaCl-BaCl_2-SrCl_2 system,the phase diagram of which as well as some isothermal sectionshave been calculated.The devations of temperature between the calculated and experimen-tal diagrams are less than five degrees.     

IN-SITU OBSERVATION OF CRACK TIP DEFORMATION IN A DUPLEX STAINLESS STEEL

The development of dislocation structures in the plastic zone ahead of a crack tip has been in-vestigated in a duplex stainless steel during in-situ deformation experiments in a scanningtransmission electron microscope.It was found that the dislocation distribution wassignificantly different in the ferrite and in the austenite.In the ferrite grains,the dislocationsemitted by the crack tip may cross-slip out of the original slip planes and form a broad plasticzone.However,in the austenite,the dislocation free zone is small and the dislocations emittedby the crack pile up in its slip plane.The selection of slip systems at the crack tip depends onthe crack tip Schmid factors in both phases.But after large deformation,the selection of thesecond slip systems at the craek tip in austenite does not depend on the Schmid factors.     

QUASI-EQUILIBRIUM MICROSTRUCTURES AND EFFECT OF ALLOY ELEMENTS IN Fe-Mn-Ni-Cr STEELS

本文利用X射线定量相分析及金相观察和硬度测试,考察了中碳Fe-Mn-Ni-Cr钢的组织及合金元素的作用。建立了经1100℃淬火后的马氏体体积分数与合金成分的定量关系式; f_M~(1100)=162.643-15.482Mn-7.36Ni-4.286(Cr+Mo+V)并在此基础上给出了亚平衡组织图。结果表明,Mn稳定奥氏体的作用大于Ni的作用。Ni和Cr当量分别以[Ni]=2.104Mn+Ni,[Cr]=Cr+Mo+V表示。计算了M_S点处的马氏体相变驱动力,指出Mn具有强烈降低相变驱动力的作用。     

MECHANISM OF NON-EQUILIBRIUM SEGREGATION OF SOLUTE TO GRAIN BOUNDARIES

本文以空位-溶质原子拖曳机制为基础,并考虑了空位、溶质原子和复合体三者的反应平衡及晶界平衡偏聚的作用,得到了溶质原子的非平衡晶界偏聚动力学方程。对硼在奥氏体中等温及连续冷却时所产生的非平衡晶界偏聚现象进行了理论计算,得到了与实验较为一致的结果。     

DRIVING FORCE OF BAINITIC TRANSFORMATION FOR Fe-Mn-C ALLOYS

本文应用三元合金的规则溶液模型计算了Fe-C-Mn三元合金在贝氏体相变温区内以不同方式等温转变的相变驱动力,从热力学上论述了以不同的微观机制进行等温贝氏体转变的可能性。     

Ni—Ti合金中双程形状记忆速动相变的研究

利用应力对双程形状记忆合金中相变驱动力的制约作用,在Ni-Ti合金中实现了不需附加机构的速动相变和速动双程形状记忆效应。