The influence of B content on the solidification and on the porosity forma-tion of cast Ni-base superalloys has been examined.Because of the solubility ofB in γ-solid solution is quite limited,the B may be enriched in melt at the frontof frozen solid during solidification.For superalloys containing more B,say 0.1%,the solidified grain may be surrounded by a much low melting point liquid coatingenriched with extreme B as high as 1%.It was found under metallographic obser-vation that their microstructure reveals as the interconnected continuous“web-likefilling channels”which expand the temperature range in molten state and reducethe residual amount of liquid unable to fill the pores.Thus,an improvement ofthe cast superalloys over both porosity elimination and technologic allowance hasbeen noticed.The liquid pools in alloys are small and isolated,and the micropo-rosities are finely distributed.For superalloys of normal B content,say about0.01%,the B did not be enriched to such extent that the liquid web was not yetformed.The solidified dentritic grains may be interconnected rather promptly alongcertain fastly growing directions,and the residual liquids isolated each other intolarge pools.In this case,the unsolidified liquid pools may be up to 30% in vol-ume of the alloys.Therefore,the more serious porosities will be resulted.

The Snoek-Kster relaxation processes in oxygen-doped high purity polycrys-talline Ta after plastic deformation were investigated.It was shown that there arefour distinct types of Snoek-Kster relaxation,namely,SK-1 and SK-2 occurringin lower oxygen concentration,i.e.,unsaturated interstitial atmosphere,as sameas peak(1)and(2)in the previous work by the authors;SK-4 in high oxygenconcentration,i.e.,saturated atmosphere and SK-5 in lower oxygen concentration,i.e.,unsaturated atmosphere.The activation parameters of these relaxations weredetermined.As the increasing of the annealing temperature and oxygen content,the gradual transition from SK-5 into SK-4 relaxation can be observed.All relax-ation processes other than SK-1 are stable on annealing.A comparison of resultsbetween previous works and this study was also made.

An electron diffraction contrast observation on the dislocation and stackingfault structure and their movement behaviour in Ni-base alloy containing 6.5% Alwas carried out by means of TEM.The experimental results show as:1.Solution heat treatment processes with different quenching rates influencesignificantly upon the defect configuration.Under high quenching speed,a lot ofmacroholes with characteristic morphology have been observed and analyzed crys-tallographically.2.After solution heat treatment specimens suffered a certain extent of defor-mation plie-ups were observed frequently.There is a critical value of deformationto induce plie-ups in this alloy.Based on the experimental facts,a new conceptabout pile up dislocation density was suggested,which may be useful to describethe relationship between strength and microstructure of the alloy.3.Some interesting reactions of pile-ups have been analyzed and discussed.An in-situ observation of movement of extensive dislocations and the morphologyof leading partials was made by successive photograph technique in TEM.It showseven if dislocations on the same slip plane and under the same thermal stress con-dition,they may be dirived in quite different degrees,some of them extend intotwo partials,the other does not.4.The moving dislocation presented various appearances,a“bow-in”like ora“bow-out”like curve,which does not always coincide with the moving direc-tion of dislocations.This can be explained in consideration of complex stress stateassociated with them.

A review using the structural factor F(S_(6c),y)was carried out for the longrange order parameters of certain A-15 type compounds composed of A_(1-y)B_y cal-culated previously by Van Routh et al.and by Wang et al.from X-ray data.Itwas found that the weight factors in objective functions for analysis and calcu-lation by them seem to be doubtful and the conclusion drawn therefrom aboutthe order-disorder states in these compounds should be reexamined.The criterionwith a minimum error on calculation of the long range order parameters may beproposed by comparison between the composition y from X-ray intensity analysisand y_0 from other accurate determination.Therefore,a neccessary condition maybe suggested for ascertaining the modified weight factors in objective functions,and then the long range order parameters,i.e.,y should be equal to or approxi-mate to y_0.

The crystal growth of Armco iron,electrolytic iron and dilute solid solutionalloys,Fe-0.05wt-%Ti and Fe-0.5wt-%Ti,has been investigated by the strain-annealtechnique.The effect of the critical strain and sheet thickness on the grain growthproperties has also been discussed.It was found that the coarse single crystalscould be easily grown up in the cold-rolled Fe-0.28wt-% Ti alloy sheet about 0.1—1mm in thickness only by single high temperature annealing in a wet or dry H_2 atmos-phere without critical strain.

The strain energy partitioning(SEP)approach,namely,a modification ofstrain-range partitioning(SRP),has been developed to predict the creep fatiguecrack initiation life for GH33A Ni-base superalloy at 700℃ and 1Cr18Ni9Ti stain-less steel at 600℃.It shows that the life can be predicted by two variables:themaximum tensile stress and the partitioned inelastic strain-range,i.e.,the strain-range component in SRP is substituted by the strain energy component in SEP.The low-cycle fatigue data at elevated temperature for these two given alloys arecorrelated and predicted to within a factor of 2 using SEP,while some numeralsof data for GH33A beyond the factor of 2 using SRP.In addition,the predica-bility of SEP versus SRP has been evaluated by 8 other alloys of high-strengthand low-ductility.It would seem that SEP is an improvement over SRP.

The formation of spherulites of graphite in cast iron containing Ce and Mgwas studied.X-ray pattern and electron probe showed the presence of Ce in theform of CeS of NaCl B1 type and of CeC_2 of b.c.tetragonal C11a type crystalstructures.On the basis of the lattice constants of CeS,MgS,graphite and CeC_2,the sizes of the hexagonal nets of Ce,Mg and of graphite are calculated.It isfound that certain Ce or Mg atoms in the hexagonal nets planes normal to[111],[111],…are in conformity with the C atoms of the hexagonal nets of graphite.Due to the difference of electronegativities between Ce and C or between Mg andC of graphite,the electrostatic coulombic force from Ce or Mg will attract the Catoms precipitated from the melted liquids of cast iron to deposite as hexagonallayers on layers of graphite along the eight directions[111],[111],…of CeS orMgS.The result is the formation of spherulites of graphite.The conformation theC atoms in CeC_2 with the Ce or Mg atoms in the hexagonal nets of CeS or MgSalong the directions[100],[010],…is also briefly introduced.

The temperature dependence of fracture toughness of materials seems to haveanalogy to that of yield strength.This similarity for low-carbon steel has beenapproached on the basis of the plastic work loss at the crack tip.Both obey theexponential law and are in agreement with experiment.The availability to enquirefor the temperature dependence of fracture toughness for certain materials otherthan low-carbon steel from that of yield strength has been also discussed.

A fracture analysis on an implant made of steel 12Ni3CrMoV containing 6ppm B was carried out of the dependence of the fracture morphology of hydrogen-induced cracking upon the hydrogen content in HAZ and upon the stress applied.It was shown that its fracture is of the quasi-cleavage(QC)crack of hydrogenembrittlement Its QC region on the fracture surface may be broadened ornarrowed with the increasing of the hydrogen content or the applied stressrespectively.The crystallographic orientation of the QC cracking in HAZ wasverified to be{110}plane by means of the etch-pit method.

Three straight lines have been obtained by plotting[Si]vs[B]in LEC GaAson the basis of infrared LVM absorption spectra and SIMS data reported in therecent literature.The difference in slope of the lines is discussed from the point ofview of the difference in the crystal growth technique used by various investi-gators.

The mechanism of hydrogen induced slow crack growth(SCG)of type 321 and310 steels and stress corrosion cracking(SCC)of type 321 steel in boiling MgCl_2solution were investigated.The tracing observation showed that the plastic zoneahead of a loaded notched tip of austenitic stainless steels,whether stable or un-stable,was enlarged continuously with time and then SCG would occur while thedelayed plastic deformation developed to a certain extent.However,the initiationand propagation of SCC of type 321 in boiling MgCl_2 solution was independentof the delayed plastic deformation.The threshold values of SCC of type 321 steelsin boiling MgCl_2 solution were much lower than that of SCG during dynamicalcharging of hydrogen at high fugacity.The morphologies of the fracture surfacesof SCC of type 321 steel differed from that of SCG,which was intensely depen-dent upon the K_I at the crack tip.These results lend support to the statement thathydrogen evolved from cathodic reaction does not play a controlling part in theSCC of stainless steel in boiling MgCl_2 solution.

The liquid-quenched structure of Fe-12.6 at.-%B alloy was identified to becomposed of the amorphous,α-Fe and an unknown metastable phase,which willtransform into a mixture of α-Fe and Fe_2B during heating under normal pressure.The remarkable effect of high pressure on the phase transition process of such alloylies in the extension of temperature range in which the unknown metastable phasewill exist and the formation of DOe——type Fe_3B.

The temperature distribution all over the metal thin sheet in the process ofelastic-plastic deformation was evaluated by the finite element analysis.With anassumption of almost lack of variance in thermal conductivity during less deforma-tion,the results of the heat field calculated from the finite element analysis usingKelvin's equation of thermal conductivity is in better agreement with that surveyedby an infrared camera.This calculation seems to be available for the thermal effectcaused by elastic-plastic deformation.

Technical aspect of using new inhibitor AlN+Sb to produce high inductiongrain oriented Si steel were investigated.The majority in process was developed inits optimum chemical composition ranges,the reheating temperature of the slab,thenormalizing and quenching regimes of the hot-rolled band,the intermediate anneal-ing treatment and the cold-rolling reduction,which acted upon the presuppositionof the new inhibitor used Their main technological availability was distinguishedfrom ones conventionally made of the inhibitor of MnS+AlN by the suitablesoluble Al content,the extension of normalizing and quenching temperaturelimitation,the reheating temperature of slab lowered down to 1250℃ in accord-ance with the adjustment of the soluble Al and C contents and the final stage ofcold-rolling reduction,as well as the final reduction controlled from 70 to 83%with two-stage cold rolling process.The magnetic properties of the 0.35 mmthick specimen without stress insulating coating are:B_(10)=1.88-1.96T,W_(15)=0.95-1.05 W/kg and W_(17)=1.24-1.37 W/kg,which has reached an advancedlevel of Hi-B grade produced by MnS and AlN inhibitor.

The hot torsion tests on low-carbon Mn-Nb steel were carried out of the es-tablishment of the constitutive equation of the power function and of the deter-mination of the relationship between flow stress of a steady state and hot ductility.An approach to the process of dynamic recrystallization was also made after con-sideration in the effect of strain accumulation.The influences of temperature,strain rate,Nb(CN)precipitation on the dynamic fractional softening have beenanalyzed.During dynamic recrystallization,the variation of activation energy orstress exponent reflects the precipitation of Nb(CN)to a certain extent.The effectof temperature and strain rate on the Nb(CN)precipitation may be quantitativelyillustrated by(?) which is defined as so-called precipitation exponent.Furthermore,the correlation among the strain rate sensitivity,temperature and shear strain hasalso been studied.

A study was made on the mechanism of oxide film removal in Al brazing byobserving the microsctructures and scanning the conditions of fillet formation.Ex-periments show that the F-ion can only break the film to form openning windowswhich act as entrance for the permeation of flux.The heavy metal ions them-selves are incapable of breaking film,but act as surfactant gradually permeate intothe film beneath at the site of grain boundaries,and are finally precipitated there.The effective removal occurs only when both F~- and surfactant are present.Thefinal removal of the film results from the spreading of molten filler.The causeof detaching film from the substrate metal is the increase of valence of Al effectedby certain oxidant contained in flux and thus disintegrates the combination betweenthem.It is concluded that the flux sheer free from oxidant can not remove thefilm.

The time differential perturbed angular correlation(TDPAC)method was em-ployed for the measurement of the hyperfine magnetic field of ~(111)Cd solute ions inhigh purity Ni.The experimental results were analysed and discussed.This trialprovides leads for further research on the hyperfine field in the ferromagnetic metalsand rare-earth elements.

Based on the Miedema′s theory of electric charge shift,a modification of Mo-reen′s model of prediction of the lattice parameters in solid solution was approachedfrom the idea of the atomic size and separation in solid solution changing withsolute concentration.The lattice parameters in both solid solution at equilibrium andextended solid solution prepared by melt quenching seem to be predicted with moreaccuracy.By this modified model,the lattice parameters of Cu-Al,Cu-Si and Ni-Al systems solid solution at equilibrium and Ag-Sn,Ag-La and Ag-Gd extendedsolid solution were calculated.They are in better agreement with the experimentalvalues than the Moreen′s.