An investigation deals with the effects of Co on the microstructure and mechanical properties of Refractoloy 26, an Fe-Cr-Ni-Co-base precipitation hardening superalloy. The experimental results show that as Co is decreased in Refractoloy 26 alloys, the weight fraction of γ′-phase as well as the average diameter of γ′ particles increases, while the γ-γ′ lattice mismatch decreases. Lowering the Co content destabilizes MC carbide in the alloy so that more grain boundary M_23C_6 and M_6 C carbides form during aging treatment, therefore, the total amount of carbides increases. The M_23C_6 carbide disappears but μ-phase forms in the alloys with 14 and 20% Co. The Co content affects both of the amount and morphologies of twin boundaries in alloys. Lowering Co content has a little influence on the tensile properties, but a great influence on the creep resistance at 565℃. In comparison with the creep results of solid solution alloys with the same composition of matrix of Refractoloy 26 alloys, the creep properties for both solid solution alloys and Refractoloy 26 alloys with different Co content depend directly on the values of stacking fault energy in matrices. It seems that a satisfying superalloy could be obtained with low Co content for which the mechanical properties are high enough for practical use and the microstructure stability is even better than that of original Refractoloy 26 alloys.

The grain coarsening behaviour towards the austenitic hot work tool steels has been studied by means of quantitative metallography. The stability of MC is improved and its volume fraction in the steel is increased by alloying element Nb added. The ratio of Ni/Mn substantially affects the grain coarsening. The volume fraction of M_23C_6 and MC carbides in the steel increases with the increase of the Ni/Mn ratio. Both Nb added and Ni/Mn ratio increased raise thegrain coarsening temperature. The modification of the Gladman's model may then be proposed by the comparison of different models of grain coarsening with assumption of uneven in convexo-concave interface along grains. The modified Gladman's expression is given as: R_o =πr/3f_v(3/-2/Z) that may fairly predict the actual grain size observed.

Measurement was carried out of the temperature dependence of the antiferromagnetic fcc Fe-Mn-Al and Fe-Mn-Cr alloys upon the electrical resistivity and magnetic susceptibility. A paramagnetic-antiferromagnetic transition together with an anomaly of resistivity of them is obtained. Owing to antiferromagnetism, ordered scattering,the anomaly of resistivity increases the dρ/dT decreases even becomes a negative divergence and the ρ-T plot turns upward at temperature below T_N. The anomalous resistivity increases with the decrease of T_N and the raise of the peak value on susceptibility. The amount of Al addition is vigorously influenced on the variation of magnetic resistivity induced by the antiferromagnetic transition. The more Al they contain, the more sharp increment it is. But the effect of Cr on the resistivity is far inferior to that of Al. As the resuit of the paramag netic-antiferromagnetic transition, it would be believed in the possibility of developing a new Fe-Mn-Al-Cr resistance alloy with low temperature coefficient.

The critical diameter of γ′ [Ni_3(Al,Ti)] particales in the transition from dislocation cutting to by-passing in a Ni-base alloy GH99 under tensile deformation at room temperature is about 60 nm. Under the same condition, the γ′ strengthening mechanism is of the dislocation cutting. To the γ′-phase, an increase in Al content makes to raise its antiphase domain boundary energy and the critical resolved shear stress on plastic deformation of the alloy. The theoretically calculated yield strength of the alloy GH99 at room temperature is close to the measured one. The γ′ precipitation strengthening contributes to the yield strength of the alloy makiing up about 45 to 64% of the total, and increases with the increase of its Al content, But the strengthening by grain boundary carbide is not worth more than 2—3%.

TEM and SEM studies were carried out on the low carbon martensitic steel 12Ni4CrMo undergone intercritical heat treatment. The influence of the quenching temperature between A_(c_1)—A_(c_3) on the morphology, phase constitution as well as -196℃ CVN toughness were analyzed in comparison with the steel conventionally treated. It is suggested that the effective grain refinement, the configuration of zigzag prior austenite grain boundary and the suitable substructure are the important microstructural characteristics of the intercritically treated steel. These seem to be the main factors contributing to the optimum toughness.

The coarse grain formation of alloy GH49 after critical deformation is caused by the direct growth of primitive grains, not the "minority of recrystallizing nuclei" or other complex details. The primary driving force of coarse grain formation in the critical deformation region is the energy difference of distortion between both sides of grain boundaries.

The M_s temperature and the yield strength of austenite have been measured for 5 various Fe-Ni-C alloys. The solution strengthening of austenite at M_s temperature can be expressed as: σ_(0·2)(M_s)=25.9+3410x_c+567x_(Ni) MPa, and the effect of C and Ni content on M_s temperature can be shown as: M_s (K)=829-8650x_c-1766x_(Ni·) The linear relationship between M_s temperature and σ_(0·2)(M_s) can be written as: σ(0·2)(M_s)=210-0.323M_s(℃) MPa. These equations indicate that the solution strengthening of austenite at M_s temperature acts as the resistance of martensitic transformation and the linear relation exists not only between σ0·2(M_s) and M_s, but also σ_(0·2)(M_s) and the driving force for martensitic transformation. Since the substructure of martensite depends on the Ni and C content in alloys, a schematic sketch showing the effect of σ_(0·2)(M_s) on the morphology of martensite in Fe-Ni-C alloys is developed through the work of Magee and Davies. Based on this view, the relationship between σ_(0·2)(M_s) and the critical resolved shear stress may be sketched which interpret the formation of dislocation and twinned martensite.

The modulated structure developed during early aging stage in Ni-38Cu-6Si and Ni-60Cu-4Cr (by at.-%) alloys have been studied by TEM in different operating conditions It has been shown that the features of wavy striation contrast in image and satellites in diffraction patterns were viewed in both Ni-Cu-Si and Ni-Cu-Cr alloys But the diserete particles distributed randomly with sharp interphase boundaries were detected in initial stages of aging by using the technique of defocussing high order reflection in bright field. However, they arrayed periodically along <100> direction after some aging time. Accordingly it is suggested that the modulated structure formed by aging at 580℃ in the two alloys is not due to spinodal decomposition The distinguishing criterions between spinodal reaction and nucleation-growth have been discussed.

Three kinds of simulated HAZ specimens of 15MnVN steel were tested. Based on metallographic and SEM examinations on fractured specimens, it has been clarified that the cleavage fracture initiates at the crack nuclei formed in M-A constituents. A statistical criterion of cleavage fracture for the specimens has been derived. It describes quantitatively the relationship among K_(IC)(or J_(IC)), σ_y, the hardening exponent, n, and the cumulative fracture probability, P, and the relationship between J_(IC) and T, by which the predicted values are in good agreement with the experimental results.

An investigation was made of the ductile fracture of ferrite nodular graphite cast iron under multiaxial tensile stress using the notched cylindrical specimens with 3 different notch root radii 2, 4 and 10mm. Numerical stress and strain distributed at notch were calculated by means of the finite element method taking into account of large elastic-plastic deformation. The nucleation and growth of cavities among the interface of graphite nodule and matrix were traced under metallographic observation on interrupted tensile testing. Experimental results showed that the ductile fracture of specimen may be caused by the nucleation, gro wth and then coalescence of cavities when the stress on the interface of graphite nodule and matrix raised up to about 650 MPa.

Stress corrosion cracking (SCC) of high-strength steel in aqueous medium in comparison to hydrogen induced cracking (HIC) during dynamic charging under mode Ⅲ loading was investigated. The threshold stress intensities for SCC and HIC under mode Ⅲ and Ⅰ were measured and compared. It was found that both SCC and HIC under mode Ⅲ loading initiated and propagated on the planes inclined at 45°to the notch plane, differing from that under mode Ⅰ loading. The fracture surfaces, however, revealed intergranular facets, similar to that under mode Ⅰ loading. The addition of thiourea decreases the threshold value for SCC under mode Ⅲ and Ⅰ loading, which was still higher than that for dynamic charging. The threshold values of both SCC and HIC under mode Ⅲ are larger than that under mode Ⅰ, i. e., K_(ⅢH)K_(ⅠH), K_(ⅢSCC)K_(ⅠSCC). Based upon the fracture mechanics analysis, this difference is attributed to the different equilibrium hydrogen concentration between mode Ⅲ and Ⅰ loading. These results give enough evidence that the SCC mechanism in high strength steel under mode Ⅲ loading is also related to hydrogen induced cracking.

The fatigue dislocation structure in an alloy ferrite steel was studied by the method of electron diffraction contrast analysis. The dislocation structure features in annealed 12CrMo steel variate after 10~7 cycles under cyclic tensile stresses. The main features of fatigue dislocation structure are dislocation jog, dipole, Ioop, deformation band, tangle and banded dislocation structure. Alloy ferrite grains are broken into blocky-like microstructure regions.

The precipitated niobium carbide is revealed to be ordered in ferrite in 3 different microalloyed steels containing Nb about 0.08—0.24%. This ordered niobium carbide may be formulated as Nb_8C_7~′(NbC_(0.875)~′) which is formed by ordered omission of its C atoms. With the reciprocal lattice indexes or orientation relationship of transformation matrix between the ordered niobium carbide and α-Fe, the composite electron diffraction patterns can be conveniently indexed.

The pattern of crystalline steps on the fracture surface of cast iron were observed by SEM. It was found that the dendrites of cast iron grow not only along <100> directions but also along <110> directions. All the crystalline steps belong to {100} and {110} planes.

The influence of P on impact toughness test and SEM observation was investigated on the 30CrMnSiA steel with pearlite, bainite and martensite-bainite mixed structures. Results showed that the cleavage element on the fracture surface increases and the impact toughness decreases as the increasing of P content. The intergranular fracture appeared till P up to 0.020%. An impact toughness sequence of various structures in the steel influenced by P may be arranged as: martensite+bainite>bainite>pearlite.

Equilibrium experiments of iron melts containing As and saturated C with CaC_2-CaF_2 slag, which was saturated with CaC_2, were carried out under highly purified Ar atmosphere at 1350, 1425 and 1500℃. The free energy of the reaction 3(CaC_2)+2[As]=(Ca_3As_2)+6[C] is found to be △G°=-88150+29.80T(J), both As and Ca_3As_2 based on the infinitely dilute or 1% by weight solution standard. A plot of 1g fCα_3As_2 νS (%Ca_3As_2) gives values of the activity coefficient of Cα_3As_2. From the experimental equilibrium data of the quarternary system Fe-As-C-j where j=Si, Mn, P, values of 1g f_(As)~j can thus be evaluated. The interaction coefficients of the activity of As in iron melts e_(As)~j, are thus obtained as follow: e_(As)~(Si) e_(As)~(Mn) e_(As)~P 1350℃ 0.064 -0.035 0 1600℃ 0.057 -0.031 0

The reduction kinetics of Fe_3O_4-(xFeS·yCu_2S)-FeO-SiO_2 system has been investigated against the slagging flux, silica granule size, mattegrade, initial magnetite content and temperature. The experimental results showed that the reaction rate increases with decreasing αFeO, matte grade and silica granule size as well as with increasing temperature. The reaction rate is controlled by the slagging reaction if the matte is saturated with Fe_3O_4, and by the reaction between S and O_2 in the melt if the matte is not saturated with Fe_3O_4. The corresponding rate equations can be expressed as: γSO_2=2.8×10~7exp(-154200/RT)W_(SiO_2)~(2/3)-α (1150-1300℃) γSO_2=3.1×10~8exp(-237900/RT)(%OFe_3O_4-b)~2(%S) (1200-1300℃) The activation energy for the reactions was found to be E_α=154.2 and E_b=237.9 kJ/mol respectively.

The effect of alkalis, fluorine or combination of both, either in vapour state or in contaminated state on the swelling properties of the pellets during reduction were studied. It was proved that the abnormal swelling of pellets contained alkalis and fluorine during reduction mainly occur in the stage of Fe_2O_3-Fe_3O_4, which was accompanied by abnormal rupture of iron oxide crystal, whereas the pellets contained high K occur obvious swelling in the stage of Fe_xO-Fe which was appeared with serious iron whisker growth. By means of step reduction of oxidized high pure Fe sample permeated with K or Na, it has been proved that the abnormal rupture of the iron oxide crystal and iron whisker growth are resulted from the high alkalis content. On the other hand, the bonding phase contained alkalisfluorine in the pellet became liquid during reduction and lost their bonding force to resist the stress caused by the volume expansion due to rupture of iron oxide crystal or iron whisker growth, thus caused more serious abnormal swelling of the pellets. From the analysis of the reduction sample by X-ray diffraction and Mossbauer spectra and study on the reduction rate at the interface between iron oxides, the causes of crystal rupture and iron whisker growth were clarified, the mechanism mode of the rupture of iron oxide crystal and iron whisker growth has also been proposed.

Taking a steel works as an example, the factors which influence overall energy consumption of the ironmaking system and their dependences were discussed with view of comprehensive energy conservation, the optimizing model of ironmaking system for energy utilization was developed. The model consists of two parts, the general model of ironmaking system and submodel of sintering process, both are nonlinear program model. The optimum charge mixture in sintering process and optimum ratio of sinter and pellet were researched by the model and optimization method, the influence of the parameters of processes on the overall energy consumption of ironmaking system was also dealt with.

The phase equilibrium relationship of the Ni-Fe-16.7 at.-%La system has been investigated by means of X-ray diffraction and DTA. The Ni-riched region has a peritectic reaction. A new hexagonal intermetallic compound LaNi_3Fe_2is identified. The absorption and desorption of hydrogen by the system and by this new compound were also examined.

The effect of rotating magnetic field annealing (RMA) on the anisotropy has been studied using a disk specimen of amorphous alloy Fe_4Co_(66)Ni_2Ta_2Si_(10)B_(16), Fe_5Co_(70)Si_(15)B_(10) and Fe_(40)Ni_(40)B_(20). The induced variation of anisotropy of the alloys on the process of isothermal annealing at 260—280℃ was measured in a rotating magnetic field with different speeds. During RMA, the value of K_u already induced in the specimen decreases monotonically with annealing time and its decreasing rate is independent of the rotation speed of field applied. The anisotropy induced by RMA in common practical conditions is very small and can be neglected. The experimental results may be explained by a simple theory proposed by the authors.

An investigation was made of the influence of modifying element Ce and of solidification rate on the structural transformation of graphite in the Fe-C-Si alloy. It is proposed that during the transformation between spheroidal and overcooled graphite or between vermicular and flake ones, the modifying element Ce added may be the main effective factor, and the critical wt-% of Ce addition for each transformation may be expressed as Ce_((S-D))=-0.0296 1g R+0.162 and Ce_((V-A))=-0.0353 1g R+0.147 respectively. The solidification rate seems to be predominant while the transformation between spheroidal and vermicular graphite, and the critical rate in μm/s to complete the spheroidal or vermicular graphite transformation may be R_s=55×10~(-2.5Ce) or R_v=32.4×10~(-2.3Ce) respectively. It is confirmed that the structural transformation between vermicular and flake graphite may be carried out continuously during the growth of graphite crystals. The graphite of vermicular structure is a special one which is growing up under certain conditions of modifying element Ce and solidification rate with no need to decay the nodularization or to break the graphite nodules prior to its growth.

Mossbauer spectra and magnetic properties for Nd_(15)Fe_(85-x)B_x (x=0-8) alloys have been measured. The effect of B content on structure of the alloys has been discussed. The Mossbauer spectrum for Nd_(15)Fe_(77)B_8 alloy with the best magnetic performance can be considered as the superposition of 6 ferromagnetic subspectra for Nd_2Fe_(14)B phase and a paramagnetic subspectrum for Nd-rich phase. It can bc estimated that there are 6% of Fe atoms in the Nd-rich phase.

Surface oxidation of amorphous Pd_(80)Si_(20) was studied by in situ observation in JEOL-200CX electron microscope under vacuum about 10~(-5) Pa and AES. An amorphous oxide layer formed evidently on the surface of the α-Pd_(80)Si_(20) specimen at a temperature around 120℃. During heating, owing to the inward movement of Si-atoms and surface oxidation, the Si content along the edge of a wedge specimen and on the surface layers of the matrix increased, and therefore made the thermal stability decreased.

The volume effect of 6 PdSi-base amorphous alloys on heating has been measured by a tension method. The fractional free volume of 3 ternary alloys at the glass transition temperature is calculated to be 0.02—0.03 which is approaching the value 0.025 of ordinary amorphous materials. The relationship between free volume increment of 6 materials in equilibrium state and relative viscosity is consistent with the viscous flow free volume model.

A new method for the simultaneous determination of the Ce subgroup and Y in Ni-base alloy or steel was developed. The trouble to analysis from the mutual overlap on the spectra resulted by the complexes of Ce sub-group and Y with chlorophosphonazo-P-NO_2 in HClO_4 has been relieved by complete separation using first derivative spectrophotometry. The interference of foreign ions can be eliminated by masking with VC, Zn-EDTA and NH_4F. The method has been applied to Ni-base alloy or steel containing 0.05—0.4% Ce sub-group and Y with a relative error ±8%.

A method for the quantitative determination of γ'-phase has been developed by direct weighing after all the matrix γ-phase of a thin foil specimen less than 0.1mm thick is dissolved by a long time potentiostatic electrolysis. The difficulty of the conventional analytical method by means of electrolyte extraction, which is caused by aggregation and growth of network γ'-phase in Ni-base superalloy containing high Al and Ti on long exposure to high temperature, has been overcome. The results obtained by this method are in agreement with that by ordinary isolation one.