Based on the Hume-Rothery rules and the connections between phase stability and electron structure, it was noticed that both the atomic radii and electronegativities of Ti with Ti_3X forming elements Al, Ga, In, Sn and Zr are favourable factors for alloying. Under the examination of atomic properties of these elements, it seems to be drawn that the electron concentration is the chief controlling factor for the a-Ti_3X-phase boundary. The investigation was made with four selected ternary alloy systems: Ti-Al-Ga, Ti-Al-Sn, Ti-Al-Zr and Ti-Al-O. The experimental resuits show that the formation of Ti_3X-phase obeys the electron concentration rule, and the valence electron number of the alloying elements depends on their own electronic structures, i.e., N_(Ti)=N_(Zr)=2 for the transition elements Ti and Zr; N_(Al)=N_(Ga)=3(S~2P~1), N_(Sn)=4(S~2P~2) and N_o=6(S~2P~4) for non-transition elements Al, Ga, Sn and O. The characteristic electron concentration for the formation of Ti_3X-phase may be expressed as:

Four ternary alloy systems, including Ti-Al-Sc, Ti-Al-V, Ti-Al-Nb and Ti-AlMo, other than previous work, were selected to investigate the behaviour of transition elements in the formation of Ti_3X-phase. Results show that the formation ofTi_3X-phase in the Ti-Al solid solution containing the transition elements Sc, V, Nb or Mo obeys the electron concentration rule as well, and the valence electron number of the transition elements depends on the structures of their d energy bands, i.e., N(Sc)=2(S~2) for the elements, e.g. Sc, on the left of Ti in the periodic table; N_v=3(d~3), N_(Nb)=4(d~4) and N_(Mo)=5(d~5) for the elements V, Nb and Mo on the right of Ti, respectively. Furthermore, it seems that the formation of Ti_3X-phase could not be'restrained by an addition of any transition element to the alloy.

The Ti_3X-phase is found to be an important factor influenced the thermal stability of Ti alloys. The tendency towards the precipitation and growth of Ti_3Xphase may be described as the value of electron concentration. A kinetics of the embrittlement process of the alloys, depending on the exposure temperature and time, has been confirmed. Taking three factors, including electron concentration, operating temperature and service time, into account, a permissible electron concentration, N_p, may be ascertained as criterion for the thermal stability of an alloy. The physical meaning of the criterion is definite. A proposal could be made that the criterion is available for the standard of quality control of the alloy production and in new alloy design. If the determination of the Al equivalent factors of various alloying elements was made by their contribution to electron concentration, the Rosenberg's empirical formula should be modified as follow: 1(％Al)+0.46(％Sn)+0.42(％Ga)+6.7(％0)≤8(wt-％)

The effect of Nb content on the y'-phase precipitation-hardened Ni-Cr-Al-Ti base superaUoy has been investigated. Results show that a moderate addition of Nb could improve both strength and ductility of the superaUoy at room and high temperatures. It was ascertained that such improvement on the strength and ductility is made principally after the strengthening Y'-phase and the grain refinement respectively.

The toughness of commercial 9 wt-% Ni steel after an intercritical heat treatment (IHT) has been compared with that of the conventionally heat treated (CHT)steel. The toughness of 9 wt-% Ni steel at —196℃ is virtually improved by IHT, and the final value is independent on the prior austenite grain size. It appears that of the benefit of IHT comes mostly from the return austenite; besides it also increases the amount of return austenite which is stable at —196℃ and distributed uniformly over all kinds of boundaries, especially lath martensite boundary. In this case, two types of austenite have been found: the austenite film on boundaries of martensite lath and the irregular blocks particles on prior austenite boundaries, sub-boundaries and so on.

The effect of Nb content on the long-time aging stability in hot strength and structure of an austenitic heat resisting steel 37Mn31Al3Cr2MoVWNbB has been investigated. It was found that the hot strength of the steel is no longer decreased and the structural stability is dependent on the shape and distribution of NbC after long-time aging at 650℃. The coarse prior NbC deteriorates the structural stability and promotes the decomposition of matrix and the growth of x-phase which embrittles the steel. Thus, it seems to be considered to cut down the Nb content in the steel.

The decomposition and precipitation of carbides in the hot-rolled Si-Fe sheets were studied by means of both high temperature metallography and differential thermal analysis. It has been found that the decomposition during heating and the precipitation during cooling start from 720 and 750℃ respectively. The shape and distribution of the precipitated carbides are markedly influenced by the cooling rate of the sheets after hot-rolling. If the cooling rate is high enough, saying up to 100℃/min, the carbides would be precipitated dispersely; while it slows down to about 1℃/min, they would be aggregated coarsely. The shape and distribution of the precipitated carbides are dependent on the efficiency of decarburization. In other words, the more disperse the carbide is, the more effective the decarburization will be. The results may provide leads for further improvement on the technology for hot-rolling Si-Fe sheet production.

X-ray diffraction analysis was used to ascertain the LaNi_5-base solid solution range in the La-Ni-Al ternary system This range at 800℃ was found to be Al< 12.2 and 31 References | Related Articles | Metrics

The 300 and 400℃ isothermal sections of the Al-rich corner of Al-Mg-Ce ternary phase diagram with composition of 0—36 wt-% Mg and 0—50 wt-% Ce have been studied by X-ray structural analysis, metallography, microhardness test and electrical resistance measurement. The regions of 4 single-phase, 8 double-phase and 4 triple-phase were detected in the given alloy composition. Two new ternary compounds T_1-and T_2-phase were found in the solid solution regions of 21—22 wt-% Mg-14.5—16 wt-% Ce and 27.5—28.5 wt-% Mg-40.5—41.5 wt-% Ce respectively. The mechanical properties at room temperature and the stress corrosion of Al-Mg alloy containing Ce have been also examined. Experimental data showed that the great improvement over SCC of the Al-Mg alloys is related to the change of their microstructure. The β-phase without Ce distributes as continuous chain structure along the grain boundary. While an addition of Ce to β-phase would destroy the continuity, eliminate the chain structure, purify the grain boundaryand form Ce-containing solution strip precipitates along the grain boundary.

Solvation extraction of W(VI) from dilute tungstate solutions by dilute organic solutions of amines was studied. It has been found that the mechanism of solvation extraction of W from dilute and concentrated tungstate solutions respectively is different. The W compound extracted into the organic phase from concentrated tungstate solutions by primary amines is indicated to be normal tungstie acid (H_2WO_4) from our earlier work. The present work indicates, however, that the W(Ⅳ)compound or complex extracted by primary amine from dilute tungstate solutions is some other tungsten compound or complex such as WO_2(OH)_2. The hydrophilie complexes were formed first during solvation extraction from dilute W solutions. The complexes are then dehydrated slowly and then transferred into the organic phase. Experiments show that the formation of hydrophilie complex is decreasedwith the increasing of concentration of electrolytes in the aqueous phase. The related infrared and ultraviolet spectra were measured and discussed. Using of tertiary amines as solvation extractant for W was also investigated. It has been found that the tertiary amine just like primary and secondary amines can be used as solvation extractants. As there is no active hydrogen atom in the molecules of tertiary amine, its power of solvation extraction is much lower in comparison with that of primary amines or secondary amines. Large excess amount of tertiary amine has to be used to arrive a high percent of extraction by solration.

The effect of the presence of inorganic salts in aqueous phase on solvent extraction of metals by an extractant could be different during extraction with different mechanisms. The salting-out effect of the extraction of W(Ⅵ), MoⅥ),V(Ⅴ) and Cr(Ⅵ) by amines under anion-exchange and solvation mechanisms respectively was studied. During solvation extraction of oxyacids of transition metals by amines, hydrophilic complexes were formed first between them. The formation of these complexes depends greatly on the activity of water molecules in the aqueous phase. The addition of inorganic salts to the aqueous phase will decrease the activity of water molecules and thus decrease the extraction of metals into the organic phase. However, during extraction of metals by amine salts with anion-exchange mechanism, the presence of inorganic salts will diminish or prevent the formation of hydrophilic complexes in the simultaneous side reaction and thus increase the percent of metals extracted by the main anion-exchange reaction. Therefore, the extraction of transition metals by amines can be increased or decreased by the addition, of inorganic salts to the aqueous phase with anion-exchange and solvation extraction mechanisms respectively. Some new viewpoints about salting-out effect in solvent extraction were proposed.

An investigation was made of the technological process for synthesis of LaNi_(5-x)Cu_x (x=0—5) alloys by reduction-diffusion, especially detailed the proportion and grain size of starting materials, the temperature and time of reaction, etc. A favourable process was developed that the samples of LaNi_(5-x)Cu_x alloy series of the CaCu_5 structure may be prepared by direct synthesis of Cu and Ni powders under reduction-diffusion at 825℃. Referred to the similar process, the related intermetallic compounds LaNi_4Zn, LaNi_(3.75)Al_(1.25) and (La_(0.8)Ti_(0.2))Ni_5 were synthesized conveniently. The stability of LaNi_(5-x)Cu_x (x=0—5) alloy specimens immersed in acids, alkalies and other various media, as well as their catalytic activity in ammonia synthesis under normal temperature and pressure were also studied and compared individually.

An attempt was made of deriving an expression for the effects of pressure and temperature on the nucleation rate under the homogeneous crystalline condition, and thereafter numbers of the Betol's crystal nuclei were calculated. The resuits were shown that a peak value may be noticed on the plot of the nucleation rate vs temperature under the condition of constant pressure, and it may shift to the direction of elevated temperature with the increasing of pressure. For substances crystallized with volume shrinkage, a similar peak value may also be presented on the nucleation rate vs pressure plot under constant temperature, and it may shift to the higher pressure with temperature increased.

The optimization method was employed to study the corrections to the geometric broadening of X-ray profile in the measurement of the mosaic size and the lattice distortion using the integral line-breadth. It was found that among the nine possible match groups of the physical broadening function, f(x), with the geometric broadening function, g(x), the correctional formulae for the geometric broadening of five outstanding ones, i. e. G-C, C-G, G-CC, CC-G or CC-CC, were improved with more simplicity, high accuracy and easy on-line applicability.

The reduction rate of FeO in molten slags of two systems FeO-CaO-SiO_2-MgO and FeO-CaO-SiO_2 by solid carbon has been determined by the method of measuring the kinetic parameters in which a combination of the initial concentration in system with the weightless rate of reductant in the reaction process was made. The reduction rate determined by this study is of an apparent first order reaction of overall wt-% of FeO. The measured apparent activation energy is 222.60 kJ/mol. The empirical equation of the rate is v=-(W_s/A)dc/dt=1453.0[exp(222600/RT)]·C Experimental results show that the convection diffusion is the rate-controlling step in the reduction of molten FeO by solid carbon.