铬钢的高温冲蚀腐蚀行为

在试验室里对一些商品含Cr钢(Cr含量从2.25—25%)进行高温冲蚀腐蚀试验表明,材料的冲蚀腐蚀阻力强烈地依赖于它的抗腐蚀能力.合金的冲蚀腐蚀阻力随着它们的Cr含量的提高而提高.当Cr含量达～9%时,材料的耐冲蚀腐蚀阻力有个飞跃.冲蚀粒子的本质和形状对冲蚀腐蚀阻力也有很大影响.最后,对材料的蜕变机理进行了探讨.     

DIFFUSION REACTIONS BETWEEN Cu AND NbTi-ALLOY

Diffusion reaction of superconductig composite NbTi/Cu assembled both mechanicallyand metallurgically,diffusion couples Ti/Cu and Nb/Cu have/been studied by means ofEPMA.The results indicate that the initial interface state of thecomposite NbTi/Cu significantly affects the forming process of intermetallic compounds atthe interface.In comparison with the metallurgically bound composite,the intermetallic com-pounds forms at a higher temperature in mechanically bound one.Therefore.the mechanicalhinding process is beneficial to the production of NbTi/Cu superconducting composite.No intermetallic compounds have been observed in Nb/Cu system.The morphology ofintermetallic phases and the sequence in which they form in Ti/Cu system are somewhatdifferent from that in NbTi/Cu.The relationship between the thickness of compound layerand annealing time obeys the rule of y~(1.5) ∝ t.     

PREFERRED ORIENTATION OF DEPOSITED TiC COATING ON STEEL BY CVD

Investigation was made of the deposited rate,surface morphology and crystal pre-ferred orientation of the dense TiC coating onto austenitic stainless steel in relationwith CH_4/TiCl_4 mole ratio and temperature adopted in CVD processing. When theCH_4/TiCl_4 ratio is low or high,the preferred orientation may be(220)or(200),respec-tively,which is mainly dependent on the equilibrium concentration of active C in vapourphase.     

MICROSTRUCTURE AND PROPERTIES OF Mn-CONTAINING TiAI ALLOYS

The microstructure of Ti-33wt-％ Al-(1.6-4.5)wt-％ Mn alloys are composed ofγ+α_2 phases,but the volume of x_2-phase is a little.Mn alloying decreases the latticeparameters a and c of γ-phase and the c/a ratio becomes nearly to one,because the atomicradius of Mn is less than the atomic radius of Ti or Al.Mn alloying promotes the formation oftwins in γ-phase and increases the ability of plastic deformation of TiAl alloys at room tem-perature.     

PHASE DIAGRAM OF PrCl_3-SrCl_2-CaCl_2 SYSTEM

Five fields corresponding to the primary crystallization of PrCl_3,Sr_3PrCl_9,α(SrCl_2,CaCl_2),α_1(CaCl_2,SrCl_2)and α_2(SrCl_2,CaCl_2)respectively,six univariant lines relatedto the secondary crystallization,one ternary eutectic(48.0 wt-％ PrCl_3,23.5 wt-％ SrCl_2;590℃)and ternary peritectic point(45.5 wt-％ PrCl_3,24.5 wt-％ SrCl_2;614℃)were determined by DTA.Attempts were also made to explore the rule governing thealteration in the phase diagram containing rare earth chloride,formation of compoundand its stability by means of polarization and counter-polarization.     

EFFECT OF OXYGEN CONTENTS ON OXYGEN POTENTIALS OF H_2O-H_2 AND H_2O-H_2-INERTS GAS MIXTURES

By taking the effect of oxygen contents into account,a new set of formulae which representsthe oxygen potentials of H_2O-H_2 and H_2O-H_2-inerts gas mixtures has been derived.Classi-cal representation is only a particular case of it.Some of the variables affecting equilibriumatmosphere when trace oxygen is present and optimum preparation of the gas mixtures to min-imize errors have been discussed.The reliability of some of previous equilibrium experimentsunder the oxygen potentials controlled by H_2O-H_2 or H_2O-H_2-inerts gas mixtures has alsobeen criticized.     

TRANSFORMATION CHARACTERISTIC OF TWO WAY SHAPE MEMORY MATERIAL CONSTRAINED BY STRESS

The snap-acting transition and two way shape memory (TWSM) effect have been obtainedin a TWSM spring made of Ni51Ti49 alloy using the constrained effect of stress on drivingforce of TWSM material.When the snap-acting transition has been realized:M_s= M_f andA_s=A_f;hysteresis is rectangular,the height (TWSM effect) and width (hysteresis) of therectangle can be readjusted by means of constrained stress.The results of resistancemeasurments show that,the snap-acting TWSM effect mentioned above was supplied mainlyfrom the transformation of P←→R.The thermodynamic model has also been proposed to ac-count for the snap-acting transformation.     

ELECTRON RADIATION INDUCED VOID SWELLING AND GRAIN BOUNDARY SEGREGATION IN AN Fe-Cr-Mn AUSTENITIC ALLOY

The behavior of void swelling and segregation in Fe-15Cr-xMn alloys and an alloy con-taining small amount of W and V was investigated by electron-irradiation.The compositionalanalysis in the irradiated regions including grain boundaries was performed.The resultdts showthat there are many common features of irradiuation tehavior in the Fe-Cr-Mn andFe-Cr-Ni systems while there are some significant differences,In the Fe-Cr-Mn alloy sys-tems void swelling was rematrkably suppressed and at the same time the radiation-inducedsegregation was also retarded,furthermore,the segregation was strongly retarded in anFe-15Cr-15Mn alloy containing small amount of W and V.The results also show that Ni re-placed by Mn does not in general confer immunity from either swelling or phase instabilities.The phase instability is due to the different diffusion behavior of Ni and Mn in reponse to theoperation of the inverse-Kirkendall effecr.Fe segregates to the microstructural sinks in theFe-Cr-Mn alloys.The segregation of Fe often leads to the formation of ferrite.This fact isbeneficial to reducing the swelling rate and segregation on the grain boundaries.     

EFFECT OF NITROGEN ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF ALLOY HK50

The volume fraction of the lamellar carbide cell in HK50 alloy may be increased with the in-crease of nitrogen content over 0.065%.The habit plane of lmellar carbide is {111}_γ.Thedistribution of nitrogen changes no more before or after the precipitation of lamellar structure.The diffusion activation energy of carbon reduces remarkably with the increase of nitrogencontent.It is believed that the lamellar carbide cell is harmful to the high temperature creepand impact properties of the alloy.     

THERMODYNAMICS OF Mn-C-j MELTS AT 1350℃

The solubility of C in Mn melt at different contents of Si at 1350℃ was determined.The sol-ubility of Ca in Mn melts containing C in CaC_2 crucible under sealed condition at 1350℃was ascertained.With these data,evaluation of the activity interaction coefficients e_C~(Si),e_C~C,e_C~(Ca) as well as γ_C~0 was made.The standard free energy of solution of C in liquid Mn basedon the 1 wt-% solution standard,formulated in relation to T,was also estimated.Brief dis-cussion was made as to the confiormability of results with those given in the literature.