By hot roiling at temperatures between 1175—900℃ and subsequently isothermal treating at 600℃, the grain size of α-Fe was refined to 7—22μm in diameter. There were a number of 3-and 2-dimensional dislocation networks and precipitates of small NbC particles in α-Fe. The lower yield stress of the alloy can be increased up to 35—42 kg/mm~2 by the combined strenthening of grain refinement, second phase particle (NbC) and dislocation substructure. The lower yield stress σ_(1y) is related to the average value of the grain diameter by Hall-Perch equation:σ_(ly)=σ_i+k_yd~(1/2) where k_y is proportional constant of strengthening by grain refinement, k_y=2.2 kg/mm~(3/2); σ_i is friction stress on moving dislocations in grains. The values of σ_i for the specimens isothermal treated for 30 see, 40 rain and 3 hr at 600℃ are 21.5, 13.5 and 13.5 kg/mm~2 respectively.The dislocation density in the alloy is increased with increasing deformation. The relationship between the square root of average dislocation density and the flow stress can be expressed in the form of the following equation:σ_f=σ_0 +αGbρ~(1/2) where G is the shear modulus; b is the magnitude of the Burgers vector;α is the strengthening proportional constant by the interaction of dislocations, α=0.37;σ_0 is the flow stress due to all cases (e. g. grain refinement and dispersion strengthening etc. ) other than dislocation interaction. With the specimens isothermal treated at 600℃ for 30 see, 40 rain and 3hr, the values of σ_0 are found to be 34, 30 and 30 kg/mm~2 respectively. Results from the analysis of experimental data and theoretical calculations have shown that the value of σ_i is the summation of the contribution to yield stress by the dispersion strengthening of second phase particle (NbC)σ_p, dislocation substructure strengthening σ_d and lattice friction stress σ_1, i. e.σ_i=σ_p+σ_d+σ_1The "precipitate growth"dislocation loops have been observed around the NbC particles precipitated in α-Fe. The mechanisms for "precipitate growth" dislocations have been discussed in this paper, but their effect on the strengthening has not yet been clarified and will be further investigated.

By applying the differential equations of motion, as well as the equations of energy, of state and of continuity, an investigation of one-dimensional air-flow phenomena in mine networks has been carried out. Both the compressibility of airflow within the branch of the network and the exchange of energy are taken into consideration in the above equations. A mathematical model for control of airflow state in mine ventilation networks has been put forwarded, and results of transient response of flow caused by underground fire, as an assumed network being calculated by digital computer, are presented as an example.

In a 35Ni-15Cr type iron-base superalloy, it has been found that, with the falling of Cr content from 15 to 12％, the oxidation resisting, as well as stressrupture and tensile properties were little effected, the latter however, appeared to vary significantly with the influence of Si contents. The σ and Laves phases were suppressed, and the microstructural stability increased with decreasing Cr and Si contents.The extracting process of G-phase by electrolytic and chemical method has been studied. By means of chemical in combination with electron probe analysis, the composition of G-phase was ascertained to be about Ni_(18)Ti_(10)Si_(16).

A formula for the calculation of rolling pressure has been derived on the following bases: flat compression instead of fiat rolling is adopted; contacting area is differentiated according to different friction role; theory of plasticity of constant strain energy is assumed.The formula thus derived may be applied with given calculating charts of rolling pressure and roll-elastic flattening which renders the rolling pressure calculation very much simplified.

The kinetics of reaction of molten cuprous sulphide with hydrogen has been investigated at 1150, 1200 and 1250℃ respectively. The kinetics equations obtained are: for single phase, u_S％=d(S％)/dτ=k_S(S％-a)~2p_(H_2)~(1/2) for two phases coexisted, u_S％=d(S％)/dτ=AP_(H_2)~(1/2) The rates of these reactions were constant when certain phase transformation occurred or two phases coexisted. The plots of these reation-rates against concentration of sulphur according following equations: showed a turning-point for each temperature. At the turning point of reaction rate, its sulphur content in cuprous sulphide melts at the beginning to form two phases are 19.805, 19.73 or 19.61 wt.％ at 1150, 1200 or 1250℃ respectively.The reaction rate constant and its activation energy have been found to be:k_(1150·C)=3.27×10~(-2), k_(1200·C)=3.76×10~(-2)and k_(1250·C)=4.12×10~(-2) min~(-1), S％~(-1), atm~(-1/2) and E=11000 cal./mol of Cu_2S. Thus the effect of temperature on the reaction rate appears to be not remarkable.Discussion has been given on relation between the phase diagram of the Cu-S system vs their reaction rates.

In multilayer welding of low-alloy high-strength steels, HAZ microcracks are generally observed at the concavities of the fusion lines near the surface layer, being about 3—7 mm beneath the surface of the plate and almost perpendicular to the fusion lines. The formation of these microcracks is closely related to local conditions of the Tusion line concavities. There is reason to believe that the concavity ("d") of the weld pool may be taken as an important indication of such local conditions. Thus, for a given base metal, the tendency of microcracks formation may increase mainly with the increase of "d", whereas the effect of energy imput during welding appears to be less important in this respect.The HAZ microcracks may be minimized by using microcrack insensitive welding condition or/and by lateral inclination of the electrod wire during welding.

Hexagonal unit cells of composite reciprocal lattice have been derived for bcc as well as for fcc twin crystals, with these models, the characteristics of electron diffraction patterns of twinning in cubic systems can be figuratively described, thus simplifying the calculating and indexing processes of these patterns.

The crack tip stress intensity factor under impact-fatigue conditions expressed by the equation K_I=(AE/BW)~(1/2)·F(a/W) may be used as a measure of fracture toughness of materials on condition that a proper calibration of K_I with the compliance measurements is made. The fracture toughness values obtained by the above method are equivalent to the dynamic fracture toughness K_(Id) with loading rate of the order (?)=10~5kg/mm~(3/2)/sec, and would be valid as the critical crack length of the fracture surface of specimens are constrained within the range of a/W=0.36-0.6.The above method is simple and convenient for testing fracture toughness of materials. The testing results may be obtained directly from a ready made curve provided that the critical crack length on fracture surface has been predetermined. It can be recommended as a screen method in practical work.

In order to verify the correlation between J-integral and strain energy previously put forward (Acta Metallurgica Sinica, 12, 1976, 162), J_(Ic) values have been determined experimentally by means of TPB type specimens with two different ratios of S/W(4 and 8). The J_(Ic) values obtained by formulaJ=2/B(W-a)(U-U_0+M~2φ/BE'W~2) are: 124-0.5 or 11.7±0.8kg/mm for S/W=4 or 8 and a/W=0.22 to 0.71 or 0.28 to 0.53 respectively. This mesns that similar J_(Ic) values are obtained from TPB specimens of different ratios S/W and a/W. It is further shown that the formula aforementioned contributes a general correlation between J-integral and strain energy.

The electron diffraction patterns of twinning in either face or body center cubic systems possess four kinds of mode for all zero layer diffraction patterns of twins which coincided with any {uvw}~* zero layer diffraction patterns of the matrix: (1) if any two among indexes u, v and w are zero, only one mode of pattern is possible; (2) if any one index is zero or all three are identical, there are two modes of patterns; (3) if any two indexes are identical, there are three modes of pattern; and (4) only if u≠v≠w≠0, four modes are present.In most cases, zero layer diffraction spots of twin coincided with that of the matrix. Special attention therefore must be paid to the presence of twin diffractions which may often be overlooked.The different types of electron diffraction patterns for twinning in cubic systems are discussed. A rapid method to detect the twin diffraction spots has been proposed.

The application of PHACOMP with a view to estimating the amount of σ-phase in complex iron-base superalloys has been carried out. Results obtained on certain commercial as well as experimental heats sustained its usefulness. The formula:△N′_V= Ni-3Ti-3.5A1-1.7Si-0.9Cr-4.7 has been found to be useful in predicting the conditions with regard to the formation of σ-phase of a 25Ni-15Cr type alloy as an example. When △N_V>0, the alloy remained σ-free after prolonged exposure at 650℃.