A study was conducted to obtain a better understanding of the effect of Fecontent on strengthening of the super strength electrical conductive Cu-Fe alloy.Under certain specified technique with Fe content about 10 at.-%,the electricalconductivity of the alloy may be up to 59—60%(IACS)and the ultimate stregthup to 6.4×10~2 MN/m~2 as well.When the Fe content over 10 at.-%,its strengthraises linearly with Fe content.It is proposed that the strengthening is mainlycaused by the fibre reinforcement of even distributed α-phase in the alloy matrixof ε-phase as a composite material.

By application of the improved KRC model for determination of △G~(γ→α),the total driving forces for transformation and driving forces for growth(nucle-ation)for the several possible mechanisms of the bainitic transformation in Fe-Calloys,i.e.,γ→α+γ_1,γ→α+Fe_3C and γ→α′(the same composition)and α′→Fe_3C+α_B(the composition of the bainitic ferrite)are calculated.The driving forceof γ→α+Fe_3C is the largest,followed by that of γ→α+γ_1 and that of γ→α′isthe smallest.The driving force for growth of γ→α′is far less than that of γ→α+γ_1.At the temperature range of bainite formation,the driving force for γ→α′ismuch lower than that required for shear mechanism.The driving force for trans-formation of γ→α+γ_1 in 0.1—0.55 wt-%C alloys at B_s temperature is onlyabout -45 J·mol~(-1).At the upper limit temperature of bainite formation,the driv-ing force of γ→α′in 0.8 wt-%C alloy-is about 137 J·mol~(-1),and that of α′→α_B+Fe_3C is—527 J·mol~(-1).If cementite precipitates from the bainitic ferrite,thetotal driving force,i.e.,the sum of the driving forces of the above two processesis only about -390 J·mol~(-1).The above results show that the formation of thebainitie ferrite by shear mechanism is thermodynamically impossible.

The effect of 0.48 wt-% Mn,in contrast to Cr or Cu,on the precipitation,critical nucleation temperature,T_c′,and structural parameters of an Al-5.0wt-%Zn-1.8wt-%Mg alloy has been investigated by means of the hardness test,optical microscopy and TEM.It was resulted that the trace Mn addition may re-fine the grain size and increase the hardness,but can not vigorously inhibit the recrys-tallization and not raise T_c′.Under the selected aging condition at 120—200℃,thealloy containing Mn has narrower PFZ and higher HV than Mn-free one.Thetrace Mn may facilitate the growth of GBP and MPt during aging at initial stageor lower temperature≤160℃;however,it will be an obvious stabilizer to retardtheir growth during aging at final stage or elevated temperature≥180℃.Theabovemention to Mn,on the contrary to Cr or Cu,seems to be explained bythe supposition which the Mn cluster would participate the nucleation of GPzone thereafter slow down the rate of the coalescence and growth as well.

A comparison was made of the action of various inhibitors to certain highpermeability oriented Si steels on the behaviour of primary and secondary recrys-tallization.It is shown that the inhibitory action of AlN is superior to that ofMnS.The suitable average diameter of the primary grains is 15—20 or 10—12μm for two-stage or single-stage cold-rolling process respectively.The stability ofprimary recrystallized matrix is more important than primary grain size.The(110)[001]secondary grains nucleated preferentially at about 1/5-1/4 thick beneathsurface layer of the hot-rolled band.Such prior secondary recrystallizationnucleus of the steel containing AlN inhibitor is in pancake-like shape and the graingrowth is anisotropy.However,the secondary grain growth of the steel containingMnS inhibitor is isotropic.It seems that the secondary grains in the neighbourhoodof the identical(110)[001]orientation may grow into contact with each otherand coalesce to coarse secondary crystals.

The kinetic process of the zigzag grain boundary formation(ZGBF)inwrought Ni-base superalloys has been investigated.It was shown that the majorphase of ZAGBF is dependent on the essence of the alloy and the parameters ofheat treatment,e.g.temperature,cooling rate etc.,when two phase,i.e.γ′andM_6C or M_(23)C_6,are co-existed along the grain boundaries.Two models,namely,ZGBF with two-phase and the migration of a segment of grain boundary,seemto be proposed.

The effect of P contents on the impact toughness of conventionally heat-treated 30CrMnSiA steel has been investigated by means of a series of impact tests.It was resulted that the impact toughness decreases remarkably with the increas-ing of P contents no less than 0.012wt-%.The observation under SEM and byAuger spectroscopy showed that the grain boundary cracking area and the P seg-regation on grain boundaries increase with the increase of P contents.The P seg-regation toward the grain boundary and the noticeable lowering of low tempera-ture impact toughness may be promoted by slow cooling after tempering.The crit-ical temperature of high temperature temper brittleness of the steel tested seemsto be 550℃.

The carbon,whether more or less,held in solution in matrix of the Ni-basesuperalloy GH99 is almost equal to about 0.019.wt-% and an excess is formedas primary carbide.The cracks in the specimen is initiated along the primary car-bide-matrix interfaces perpendicular to the direction of stress applied during thestress rupture testing.A critical size of the primary carbide for crack initiationis found to be 0.80±0.05 μm.The more the carbon contained in the alloy,themore the primary carbide no less the critical size is,and the more severely itsstress rupture life lowers.However,the amount of primary carbide up to thiscritical size may be remarkably reduced by limiting the carbon addition below0.05 wt-%.It was also resulted that the carbide,M_(23)C_6,along the longitudinalgrain boundaries parallel to the stress applied migrate toward the transverse grainboundaries normal to the stress applied,and the M_(23)C_6 along transverse grainboundaries may be coagulated and linked together.Thus,it would weaken the grainboundary strength and injure the stress rupture property of the alloy.The rate ofits coagulation seems to related to the carbon contained in the alloy,the morethe carbon content,the faster the rate is.

The cyclic stress-strain response and microstructure were studied on LCF speci-mens of 15Cr-27Ni-1.8Ti-Fe alloy.The strain control LCF tests were performedat 600℃ under two different wave shapes:R=-1 and fixed ε_(max).Comparingthe results of these tests,the detrimental effect of average tensile stress was prov-ed.This was concerned with the influence of tensile stress on the movements ofdislocations and the formation of cracks.The observations of dislocation structure indicated that during the cyclingboth mechanisms caused cyclic hardening and cyclic softening were taking place.Cyclic strain led to generate the stress field at the interface of γ and γ′phasesfirst.As a result of increasing stress field the dislocations were created.The densi-ty of dislocation was further increased by the movement of dislocations themself.The interactions between dislocations and γ′particles degenerated from pair disloca-tion cutting γ′particles to single dislocation cutting γ′particles.It led to formmore faults and ABP's,and the γ′particles became propressively harder to shearand ultimately led to dislocations looping around particles.A typical dislocation structure of persistant slip band,ladder-like structure,wasseen as a saturated dislocation structure in the slip band,and the more ladder-likestructure formed,the more cyclic softening happened.The slip band extends to grain boundaries and twin boundaries.The grain disloca-tion interacted with boundaries,and led to complex boundary dislocation struc-ture.The density of dislocation near grain boundaries and twin boundaries wasmuch higher than others since the boundaries can acted as the barrier and disloca-tion generator.This would cause to form grain boundary cracks and twin boun-dary cracks.

The valence electron structure of the Fe-Cr σ-phase was analyzed by themethod of the bond distances based on the empirical electron theory of solidsor molecules.The covalent bond electrons are shown to be remarkably distributedirregularly.This seems to be one of the possible reason why the Fe-Cr σ-phaseembrittles.

Equilibrium oxygen activities in Fe-Nb-O melts containing 0.004 to 3.80wt-% Nb were determined by oxygen concentration cell with solid electrolyte ZrO_2(MgO)at 1833,1873 and 1913 K.The deoxidation products were identified byX-ray diffraction analysis to be tetragonal NbO_2 with a rutile structure whenNb>0.20 wt-%,to be Nb_2O_5 when Nb content being in the range of 0.05 to0.20 wt-% and to be FeNb_2O_6 when Nb<0.05 wt-%.With decreasing Nb content,i.e.with increasing oxygen activity,the form of the deoxidation products changesin the following order:NbO_2→Nb_2O_5→FeNb_2O_6With the experimental data the Nb-O equilibrium constants and other relatedthermodynamic parameters in the range of 1833 to 1913 K were calculated.

The ~1H chemical shift of ZnCl_2 aqueous solution has been measured by N.M.R.The hydration number of Zn~(2+)cation,equal to 3.8,was determined accordingto semi-empirical relationship between ~1H chemical shift,temperature T and concen-tration of ZnCl_2.The compositions of coordination compounds which are formedin TBP-CCl_4 extracting ZnCl_2 were studied by ~1H and ~(13)C N M R,as ZnCl_2·2TBP·2H_2O and ZnCl_2·2TBP.The phenomena of N.M.R.proved that part of waterreally combined with ZnCl_2 to form coordination in ZnCl_2-TBP-CCl_4-H_2O system.

The room temperature section of the phase diagram of the ternary Y-Cu-Nisystem for Y≤16.7 at.-% has been determined by X-ray powder diffractionmethod.Four single-phase regions:α,β,ε and ω;five two-phase regions:α+β,α+ε,α+ω,β+ω and ε+ω;and two three-phase regions:α+β+ω and α+ε+ωare found in the section.X-ray analysis showed that maximum solubility of Y inα-phase is about 2 wt-%.

The room temperature section of the phase diagram of the ternary Dy-Co-Nisystem for Dy≤35.6 wt-% has been determined by X-ray powder diffractionmethod.The following phases were observed:five single-phase regions:α,β,Dy_2Co_(17),Dy_2Ni_(17)and DyNi_(5-5x)Co_(5x)(x≤0.33);six two-phase regions:α+β,α+Dy_2Co_(17),β+DyNi_5,β+Dy_2Ni_(17),Dy_2Co_7+Dy_2Co_(17)and DyNi_5+Dy_2Ni_(17);four three-phaseregions:α+β+Dy_2Co_(17),β+DyNi_5+Dy_2Co_(17),β+DyNi_5+Dy_2Ni_(17)and DyNi_5+Dy_2Co_7+Dy_2Co_(17).No evidence of new phase has been observed in this range.

The design of a mode of the spatially truncated rigid cone element to con-form with the metal flow was made by the application of the upper bound the-ory-upper bound element technique.The problem to estimate the upper bound ofaxisymmetric extrusion deformation force may be solved consequently.Solutioncalculated by this mode after trial done on practice is in agreement with the actu-al one and the precision of calculation of the extrusion force seems to be muchimproved.

The m-C-δ or m-k-δ relations(simply called m-δ relation)have been obtainedfor the Zn-5%Al eutectic alloy with three average strain rates:3.7×10~(-2),7.4×10~(-2)and 1.1×10~(-1) min~(-1),at five temperatures:170,190,210,230 and 250℃.It was found that all m values increased rapidly with the increase in strainat the start,till a certain strain,called limit strain,was reached and then decreasedslowly and remained steady till fracture.A peak m value corresponding to the limitstrain may be found on each curve.The equation suggested by one of the authorscan apply to this alloy and all C values including C_I and C_F has been calculatedfor every point on all m-C-δ or m-k-δ curves.The plots of relations of C vs δ arenearly straight lines.The slopes of these lines fall suddenly at the limit strain.

Based on the Hart's differential constitutive equation,an attempt was made toderive an expression for the correlation among m-n-δ including the effects of boththe strain hardening,n,and strain-rate sensitivity,m,as follow:(?)and the simplified form:(?)It was found that this expression is in agreement with the current analysis of them-δ relations given by Ghosh and Ayres,or with the classical analysis by Con-sidère while n=0 or m=0 respectively.The calculated results of abovementionedexpression in contrast to experiments are coincidence.

An analysis of the two principal factors,namely,the change of m valuesand the divergency of initial non-uniformity,affected on the disorder of the m-δrelations in experiments has been discussed.Including either m value variation orinitial mechanical and geometrical defects,the expression of the m-δ relations wasderived respectively,and the equivalence of these two initial non-uniformities atstate of superplasticity,n=0,was ascertained.It resulted that certain experimentaldata collected for quite a few alloys seem to be possibly incorporated in the the-oretically calculated plots under consideration of above-mentioned factors.

A new expression of the quantitative phase analysis by X-ray without anyrelative calibration standard has been derived in the case of every sample,inwhich the composition of one phase is known,among those able to meet therequirements of Zevin's method.This one phase of known composition may beone of the sample,its weight fraction identified by any another method,or anartificially mixed foreign phase with certain weight fraction determined by weight-ing method.In the new expression,the weight fraction of any phase dependsonly upon the intensity ratio of each phase to known one in every sample.Itdistinguishes the Zevin's method from that the absorption coefficients of the sam-ples or the phases need not given and the experimental conditions for every sam-ple had not to be kept identical.The reliability of the new method has alsobeen verified by experiments.