MICROSTRUCTURE OF RAPIDLY SOLIDIFIED TiAl ALLOY POWDER

The rapidly solidified powder of Ti-34Al-2Mn alloy was obtained by means of ultrasonicgas atomisation (USGA) technique.The tupical size of the powder is 27 μm.X-ray diffractionresults show that the powder consists of major α_2-phase and minor γ-phase.Under opticalmicroscope both equiaxed and dendritical microstructure features were observed on RS pow-der sections.After annealing at 900 ℃/for 2 h in vacuum,most of α_2-phase transforms intoγ-phase,resulting in refinement of structure.     

CRYSTAL STRUCTURE OF γ-Li_xFe_2O_3 WITH ELECTROCHEMICAL INSERTION OF Li

Crystal structure of γ-Li_xFe_2O_3,inserted Li electrochemically,was studied by Moss-bauer spectroscopy together with X-ray diffraction,XPS and electrochemical method,Onthe insertion of Li at low current density,the crystal structure is keeping original spinel;while at higher current density or by thermal activation,owing to violent movement ofLi~+ ions,part of crystal structure transforms into rock type similar to face-centeredcubic structure of ferrous oxide.The transition channels during insertion of Li~+ ions andlimitation of Li~+ ions inserted were discussed.     

EFFECT OF FINE GRINDING ACTIVATION ON LEACHING BEHAVIOUR OF SCHEELITE CONCENTRATE

The influence of mechanical activation on the leaching behaviour of scheelite was studied bymeans of fine grinding in an attritor and subsequently HCl leaching in presence of PO_4~(3-).Results showed that after fine grinding in the attritor,the reaction rate of scheelitewith HCl-Na_3PO_4 solution was remarkably increased,the extraction of W increased fromabout 8 to 99%.The IR spectra and X-ray diffraction analysis indicated that in addition toan enlargement of surface area the fine grinding action had made also changes of fine struc-ture and reactivity of solid surface,hence the leaching process of scheelite can be carried outunder mild leaching conditions.     

填隙Ti2Ni相形成条件的模式识别分析

在多维键参数空间中对填隙Ti_2Ni相化合物的形成条件做模式识别分析,由于前过渡金属原子组成的八面体空穴中填入C,N.O原子使Ti_2Ni结构稳定化,此结构的分布区扩大,邻近的Al_2Cu,MoSi_2结构分布区减小。     

黄铜中纳米级微裂纹的形核与钝化

黄铜薄膜试样在透射电镜中原位拉伸观察表明，在平衡条件下加载裂发出的位错纯化成无位错区，它是一个应变很高的异常弹性区。当缺口足够锐，外加载荷足够大时，这个非线弹性区中的应力有可能达到原子键合力，从而使纳米级微裂纹在无位错区中不连续形核，或从钝化的原裂纹顶端形核。这个微裂纹一昊形核，即使保持恒位移，也将钝化成空洞或缺口。     

EFFECT OF ALLOY ELEMENTS ON QUASIEQUILIBRIUM MICROSTRUCTURE IN Fe-Mn-Ni-Cr STEELS

The microstructures of Fe-Mn-Ni-Cr steels with medium carbon and the effect of alloy ele-ments on them have been investigated by means of X-ray diffraction quantitative phase ana-lyses,metallography and hardness tests.The volume fraction of martensite in steels quenchedat 1100℃ can be expressed as:f_M~(1100)=162.643-15.482Mn-7.36Ni-4.286(Cr+Mo+V)Based on this expression,the quasi-equilibrium microstructure diagram has been obtained.Itis shown that the effect of Mn on the austenite stability is greater than that of Ni.The equiva-lent [Ni]=2.104Mn+Ni and equivalent [Cr]=Cr+Mo+V.The driving force for martensite transformation at M_s point has been calculated to hedrastically decreased by element Mn.     

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。     

AN ACCURATE MATHEMATICAL MODEL OF ROLL FLATTENED ARC LENGTH

本工作试验成功了一种测量压扁弧长的新方法——接触法。它能在正常轧制变形条件下精确地测量总弧长l′以及轧辊联心线前、后的分段长度x_1与x_0。 对比实验结果分析了Hitchcock,Ford,等理论公式.证实了Hitchcock公式存在一个随压下率ε减小而增大的、偏低的系统误差。 发现了理论公式计算弧长的误差主要集中在x_0部分,从而指明提高理论解精度的关键在于校正此部分的计算。 在采用弹性理论计算轧辊与轧件弹性位移量的基础上,根据几何关系确定弧长的方程结构;统计分析实验数据估计x_0部分的校正因子。按照以上方案,建立了较精确的压扁弧长数学模型。 预报结果证实该模型与简化的Stone轧制力公式联解P与l′时,具有较高的精度。     

APPLICATION OF PHASE DIAGRAMS TO SLAG ATTACK ON MgO-CaO REFRACTORIES

本文根据有关三元系等温截面图和四元系存在的液相区与固相区,分析讨论了各种氧化物、一般炼钢渣以及含磷炼钢渣对MgO-CaO系材料的侵蚀。通过分析得出,无论是一般炼钢渣或是含磷炼钢渣,都以含有一定量CaO的MgO-CaO材料作炉衬较好。