The Stability of Rare Earth-Iron-Nitrides Sm_2(Fe,M)_(17)N_y,Permanent Magnets

The effects of the partial substitution of element M(M=Cr,V,Mn,x=0.05;Zr,Ga,x=0.017;Si,x=0.15;Co,x=0.10)for Fe in samarium-iron-nitride Sm_2(Fe_(1-x)M_x)_(17)N_y compounds on their stabilitiesand Curie temperatures have been studied.It is found that Co,Ga can raise the Curie temperature of thecompounds.The initial decomposition temperatures cannot be raised significantly by all the studied elementsexcept Co.The result contradicts the formation enthalpy consideration.The final decomposition tempera-tures can be raised by all of the substitution elements.The effects of atmospheres on their decomposition be-havior were also studied.The results show that oxidation is the major reason for magnetic deterioration ofthe powder heated in air.Compared with nitrogen atmosphere,argon or vacuum helps to delay the decompo-sition of the compounds.     

Unusual W-shaped Galvanic Cell Model of ISCC of α-brass in Neutral Mattsson''''s Solution

Intergranular stress corrosion cracking(ISCC) of α-brass in neutral Mattsson's solutionwas found to be controlled by an unusual"W"-shaped galvanic cell whose cathode is thegrain boundary oxide film (G.B.0. film) andsurface film and the anode is fresh metal atthe cracked tip on both sides of the G.B.0.film. Redox reactions involved in the cellhave been proposed here. According to thismdel, initidtion of ISCC is caused by therupturing of surface film along grain boundaries,thus forming a galvanic cell. Propagation ofISCC resulted from alternate advances of G.B.0.film and dissolution on both sides of G.B.0.film caused by the effect of electrochemicalreaction. This work developed an effective approachto investigate the embrittlement process atthe tip of the crack, by increasing the lengthof the embrittlement region through constantstrain test and distinguishing the morphologyand the nature of the corrosion products byoptical microscopy and scanning electronmicroscopy (SEH).     

铸造镍基高温合金的蠕变阻力

在对颗粒强化理论和位错蠕变理论进行回顾、评价基础上，发展了一个位错蠕变阻力模型，认为蠕变阻力是影响铸造镍基高温合金蠕变机制的重要因素。当施加应力足以使位错切入γ′相时，主要蠕变机制是位错切割γ′相过程，蠕变阻力就是位错切入γ′相的临界门槛应力。在低施加应力区，位错只能借助于热激活攀移过程通过γ′相。蠕变阻力包括两部分：第一项是位错攀移临界门槛应力，与施加应力无关；第二项是与施加应力有关的阻力项，代表了其他强化机制的贡献。位错攀移机制蠕变阻力的上限是切割机制门槛应力。在3种铸造镍基高温合金中（定向凝固DZ17G合金，IN100合金和IN738合金），对上述模型进行了验证，理论计算应用了SL强化理论，与实测值符合较好。     

快速凝固Al—Li—Mg—Zr合金粉末粒度对组织和性能影响

研究超音雾化快速凝固Al—Li—Mg—Zr合金粉末粒度对组织和性能的影响中发现,粉末粒度越细,组织越细,合金强度越大;但粒度太细,又会导致塑性变差。试验合金粒度范围选用40—100μm为佳。     

CYCLIC DEFORMATION OF COARSE GRAINED POLYCRYSTALLINE PURE Al——Ⅱ.FRACTURE SURFACE MORPHOLOGY

SEM photos for very coarse grained and high ductile polycrystalline pure Al show followingcharacteristics:A few fracture sources are concentrated,the crack propagates in fan-shapenear them,and the fatigue striations are cyclic cleavage facets.Each striation consists of awide cleavage facet and a narrow cleavage stage.Those stages often blunt due to plasticdeformation.The fatigue striations are clear and continual,and distribute over whole zone ofstage Ⅱ crack propagation.Two kinds of fatigue striations form in different levels,areconjoined by a“twisted baked piece of pastry”band.The secondary crack along the fatiguestriations was observed frequently.Some of them have already developed into secondarymacrocracks and secondary fatigue striations were found clearly on secondary fracture sur-face.The fracture surface can be divided into two parts,initiation and propagation zone of thecrack,however,no statical-fracture zone was observed.The mechanism to form striationswas preliminarily discussed.     

MICROSTRUCTURE STUDY OF CONSTITUENT PHASES IN 2024 SERIES Al ALLOYS

X-ray microanalysis,convergent beam electron diffraction(CBD)and selected area electrondiffraction(SAD)studies on the structures and compositions of the constituent phases in2024 series Al alloys have been conducted.Partial substitution of alloying elements is found tooccur in all the constituent phases,which cause small deviations from the stoichiometric com-positions reported in these ternary compounds.The dominant phase is α-Al_(12)(FeMn)_3Si whichhas a body center cubic crystal structure with the Im■ space group and a=1.25 nm.The nextdominant phase is Cu_2FeAl_7 which has a primitive tetragonal crystal structure with theP4/mnc space group and a=0.6336 nm,c=1.487 nm.The minor phase is α'-Al_(12)Fe_3Si hav-ing α primitive cubic crystal structure with the Pm■ space group and α=1.27 nm.     

速动形状记忆合金元件设计原理

提出了评价速动双程形状记忆元件性能的主要参数,并说明了设计实用速动元件的原理和方法。     

Effect of heat treatment on the microstructure and hardness of C-Cr-W-Mo-V-RE Fe-based hardfacing layer

0IntroductionHot-rollers and scissors are the critical parts of thesteel rolling equipments.At present,the surface soften-ing,the early wearing and the tearing are the primary rea-sons for the lowservice life of the hot-rollers and scissors.Although hardfacing has been applied to repaire the partseasily being worn and torn,such as the hot-rollers and thescissors,and has been obtained economic benefits[1-3],this technology has common problem:if the hardfacing lay-er contains more excessive allo…     

Ni3Al中B和Mg的非平衡晶界共偏聚

在1023－1373K的初始温度和0.05-268.91K/s的冷速范围内，用Auger剖层分析确定含B和Mg的Ni3Al合金中B和Mg的非平衡晶界共偏聚行为，按照溶质－空位复合体迁移机制所导出的描述非平衡晶界偏聚的扩散速率方程解析表达式，很好地模拟了本实验结果，并确定了Ni3Al-B-Mg合金中B及B－空位复合体，Mg及Mg-空位复合体的扩散系数及复合体激活能。     

预形变和时效Al-2.73Li合金的断裂机制SCIEI

本文研究了预先冷形变对Al-2.73Li合金的机械性能和断裂行为的影响。试验结果表明,预先冷形变使合金的加工硬化率和强度提高,相应损失部分塑性。预先冷形变造成不均匀分布的胞状位错结构及晶界无沉淀带加工硬化,乃是导致塑性下降的主要原因。合金的断裂方式为沿晶和穿晶混合型。预形变后时效使沿晶断裂倾向增大。最后探讨了其断裂机制。