Study was made of the influence of the laserglaze on the micro-structure and the wear resistance of a cast Ni-base superalloy containing abundance of refractory metals, i. e. Mo 33 wt-％ and W 17 wt-％. Owing to the high contents of Mo and W, this new alloy makes its cast structure coarse and. seriously segregated and forms a large amount of phases of higher melting point. Experimental results show that the microstructure of such superalloy may be extraordinarily improved after surface treatment by laserglaze of very high energy density. All high melting point phases vanish. The solid solubility increases greatly. The crystalline structure becomes finer. The fine dendritic, cellular dendritic, cellular and plane front solidification structures are found in various parts of melted region. In the laser melted zone, the alloying elements distribute uniformly. Thus, the segregation in the alloy may be substantially eliminated by the treatment of this new technique. The change of its microstructure favours the further improvement of the properties, e. g. , the hardness of the laser melted zone is evidently increased and the wear resistance both in dry environment and in acid medium is also enhanced.

An evaluation was made of the fatigue crack propagation rate at constant amplitude of cyclic load ratio R=0.5 for the three-point bend specimens of 15MnVN steel quenched and tempered at 200℃. The monotonic plastic [zone size of the fatigue crack tip was measured under observation of phase contract microscope with the relief phenomenon out from the smooth [surface of metal during plastic deformation. The monotonic plastic zone size, perpendicular to the direction of crack surface, under plane stress is proportional to the corresponding (K_(max)/σ_s)~2. Its proportional coefficient is 0.21. According to the relationship between Rice's reversed cyclic and the monotonic plastic zone size, an exponential relation is obtained between the reversed cyclic plastic zone size perpendicular to the direction of crack surface and the related fatigue crack propagation rate. In the process of fatigue crack propagation, when the relative crack size α/W is about 0.687, the plastic zone of crack tip varies from a small [to broad scale. At α/W<0.687, the plastic deformation of crack tip spreads out in two sides of angle θ about 30—60°. While α/W>0.687, it spreads out not only in enlarged angle but also in considerably extent near θ=0°. The metaUographic and SEM observations show that the fatigue crack of 15MnVN steel with platelet martensite structure propagates along transgranular cleavage, i. e. a regenerated nuclear propagation mechanism.

The low cyclic fatigue (LCF) crack growth rate was measured by means of controlling deflection on a superalloy at 600℃ in open air. The parameter of elastic-plastic fracture mechanics, J-integral was chosen as controlling variable and the relation dα/dN=1.26×10~(-4)(△J)~(1.96) was obtained. It was pointed that how J-integral (△J_t, △J_e, △J_p) varied versus deflection δ within gage length in cyclic loading. The suitableness and limitation were discussed on stress intensity factor △K as controlling variable of a crack growth. Fracture analysis showed that accumulative damage under creep/fatigue interaction made the fracture morphology changed from transgranular striation to intergranular mechanism which characterizes creep fracture.

An investigation was made of the effects of 0.15％ RE mischmetal addition on the creep-rupture strength and ductility of Cr18Ni18Si2 austenitic stainless steel. The examinations of creep damage and fracture morphology by means of optical and scanning electron microscopy were also carried out to clarify a general aspect for the effects of RE addition on creep-rupture mechanism. The results show that the creep-rupture lives of containing 0.064％RE Cr18Ni18Si2 steel at 650 to 750℃ under 5—10 kgf/mm~2 are greater than those of the steel without RE by factors of about 1 to 4. The creep-rupture strength at 700℃ for 1000 h increases 2 kgf/mm~2 over. The creep-rupture ductility enhances by 0.2 to 2. The fractures of creep-ruptured specimens transit from typical ductile intergranular to mixed mode consisting of major ductile intergranular fracture and minor transgranular tearing. The typical wedge-type cracks form at the triple grain boundary junctions. The average density and length of wedge-type cracks in specimens with RE addition are smaller than that without RE. It is apparent that the creep-rupture process of Cr18Ni18Si2 steel is controlled by grain boundary sliding-stress concentration mechanism. The observations on fracture and creep damage may suggest that the RE addition can strengthen the grain boundary, inhibit their sliding, hence decrease the level of stress concentration at the grain corners. On the other hand, because the deformation resistance within the grains is decreased by RE addition, therefore, the stress concentration may be relaxed by the adjustment due to deformation of adjacent grains. Consequently, it is not easy for cracks to nucleate and propagate in steel Cr18Ni18Si2 with RE addition, resulting in the improvement in creep-rupture properties.

Temper embrittlement of CrMoV turbine rotor steel with 0.04％ P aged at 480℃ after a higher temperature aging for 1000h (preaging) has been compared with that of the conventional heat treated steel with the same composition. The preaging virtually accelerated the rise in transition temperature. This is believed to be conneeted with the depletion of Mo, a scavenger of P, in matrix due to the Mo tithed carbides formation during preaging. Therefore, more P is released and segregated to grain boundaries. Carbide coarsening perhaps contributed to the increment in transition temperature too.

In the case of elastic interaction between dislocations and points defects, complex interaction mechanisms can appear, which involve simultaneously depinningrepinning process and dragging processes.

An equation for calculating △G intthe martensitic trasformation of the low alloying multicomponent steels has been suggested as: being proved by the mathematic analyses and verified by the practical data of 20CrMnTi steel. The amount of the retained austenite in a hardened steel can be estimated by the equation together with the kinetic formula.

Two kinds of band structure were detected in the Ni-Mo-Al-V directionally solidified eutectie alloys. One is called the "blocky" band with discrete α-Mo particles, and the other is the "white" band without α-Mo fibre. Both bands seriously deteriorate the mechanical properties of the alloys. By using the glow discharge emission spectroscopy, the chemical composition of band structures was analyzed layer by layer. Based on the composition variation and constitutional supercooling theory, the cause of band formation has also been discussed.

The behaviour of hydrogen induced delayed cracking (HIDC, i. e. slow crack growth) in a type 310 and a type 16-20-20 (K55) stable austenitic stainless steels along with a type 321 unstable austenitic stainless steel were investigated with a single-edge notched tensile specimen. It was found that HIDC could occur in all 3 types of stainless steels and the threshold values were K_(IH)/K_c =0.55, 0.70 and 0.80 for stainless steels 321, 310 and K-55 respectively, if the specimens were charged with load. HIDC could also occur if the precharged specimens were tested under constant load in air. No HIDC, however, occurred in the precharged and then outgassed specimens. It indicates that the delayed cracking in stable austenitic stainless steels is induced by atomic hydrogen. Because there is no hydrogen induced α' martensite in type 310 and K-55 stainless steel, the existence of α' is not necessary for the oecurrenee of HIDC in the austenitic stainless steels, though it can facilitate HIDC. The mode of hydrogen induced delayed fracture in either stable or unstable austenitie stainless steels is correlated with K_I value, the fracture surface was changed from ductile to brittle as K_I is decreased.

An investigation was conducted to examine the effect of Ce addition from 0.02 to 0.24 wt-％ on the microstructure and mechanical properties of Ti-5Al-5Mo-2Sn-0.25Si cast alloy. The correlation between Ce and other alloying elements, the form and behaviour as well as the strengthening mechanism of Ce have also been studied. It is shown that the Ce addition at trace level has almost no influence on the room temperature tensile properties of the ahoy, but improves obviously its stress-rupture properties at elevated temperatures. A superior combination of its mechanical properties lies on 0.02—0.03％ Ce added. The reason why it has strengthened may be the result of the dispersion-strengthening of cerium oxide particles, the stabilization of dislocation substructures and the purification of grain boundaries.

A comparison study has been made of the modification of Al-Si eutectic alloys with modifiers Na, Sr and La by metallography and SEM. It has been found that the concentrations of just entire modification of the modifiers in eutectic alloys were aU about 0.03 at.-％. It shows that the modification is influenced directly by the number of modifier atoms rather than weight. In SEM study, the Si phase was extracted out from the eutectics with HCl+ H_2O_2 followed by dil. HCl wash. Detailed observation found that the appearance of Si fibres at entire modification were something different with various modifiers used, the shortest were the crystals modified with La, Sr the next, and that of Na-modified were longer. This phenomenon was regarded as by the influence of valence electron charges of different modifiers. The SEM observation of annealed Si extracted from eutectic bulks found that the eutectic Si phase gradually dissolved in α-Al phase while new ball form equilibrium crystals grew up. The dissolve speed of Si phase dicreased with the modifier order La, Sr, Na. No evidence was found about the dissolve of primary Si phase even annealed over 144 h. It has suggested that the modified Si phase is in unequilibrium, the higher the valence electron charges of the modifiers the more unequilibrium of the Si crystals will be. The primary Si closed to the equilibrium state which therefore can not be modified in general situation.

When the Fe-23Cr-6Al alloy is under oxidation at 1300℃, the α-Al_2O_3 grains of single layer are formed initially as columnar crystals, and then, their columnar feature degenerated progressively owing to the columnar grains growing along transverse direction and the development of outer layer oxide consisted of equiaxial crystals. If the RE added, the growth rate of columnar grain along longitudinal direction is increased and along transverse direction decreased, as well as the growth rate of equiaxial grain of outer layer oxide also decreased. Consequently, their columnar feature become more intensive. For the alloy without RE, more crystalline whiskers and fine crystals are found on the surface of oxide layer. It may be considered that the Al ions diffusion through α-Al_2O_3 layer outwards is prevented by RE addition, and the oxide layer adherence is then improved.

The disaccommodation that is not recovered by demagnetization under isothermally aging for the amorphous alloy (Fe_(0.1)Ni_(0.5)Co_(0.4))_(78)Si_8B_(14) has been measured by using an automatic equipment. Consequently, the kinetical behaviour of the low temperature structural relaxation of the alloy was studied, as well as its activation energy and the relaxation spectrum were evaluated. The results show that its low temperature structural relaxation is a multiple relaxation process with low average activation energy, in which a chemical short range order (CSRO) is developed.

The thermal stability and the crystallization of PdTa_1Si_(16.5) alloy of different glassy states have been studied by means of the differential scanning calorimeter (DSC). The behaviour of glass transformation and crystallization as well as the thermal stability in both states as-quenched and as-annealed are varied with the non-crystalline alloys of different glassy state owing to change of the quenching rates.

The magnetic structural properties and the effect of trace in Pr mingled upon the structure and properties of the Fe-Ni Invar alloy have been analyzed by M(?)ssbauer spectrum. It was resulted that the co-existence of Fe ions with ferromagnetism and anti-ferromagnetism seems to the nature of the alloy having the Invar charater. And the Invar character of the Fe-Ni Invar alloy maintains even mingled with a trace of Pr, yet its macro-magnetism is reduced.

Studies were made of the existing form and the distribution of Si in the Al-Si high temperature coating to K-3 alloy under the state of thermal permeation or static high temperature oxidation. It was found that the Si exists in the coating under the thermal permeation state mainly in the form of silieides, e.g., (Ni, Cr)_3 Si, (Mo,W, Ti)Si_2 and Ti_5Si_3, which dispersively distributes over the 40μm deep zone of the outer β-NiAl phase layer as small particles. While in the coating under static high temperature oxidation, not only its own phase structure but also the existing form and distribution of Si in it are changed. Two chief changed forms of Si are occurred as silicate at the surface and as solid solution in M_6C carbides phase in the interior of the coating. The Si-containing M_6C carbides form a barrier between the coating and the alloy substrate.

Studies were made of the mechanical alloying of an oxide dispersion strengthened majority γ'-phase Ni-base superalloy by analyses of SEM and X-rays. By a high energy ball milling technique, a mechanical solid-solution may be formed and the mechanical alloying may be realized from various raw metal powders, The CrNi-based masteralloy and elements such as W, Mo, Ta, etc. in the raw metal powders were continually solid-soluble into Ni matrix and the lattice parameter of Ni-base solid-solution was increased with processing time. Simultaneously, nearly random dispersion of the ultraflne oxide particles was obtained in the metal matrix. Although the micro-area compositions of the mechanical solid-solution is segregated, yet it may be improved by certain effective steps. The technical parameters of the mechanical alloying in aUoy studied were also analyzed and discussed.

Changes in the surface composition of Ag-Pd alloy under argon ion bombardment have been monitored by XPS. It is shown that the surface of the alloy isrich in Ag after annealing and is rich in Pd after ion bombardment due to their different surface binding energy. The component sputtering yield ratio S_(Ag)/S_(Pd) is obtained using Shimizu model. The experiment and its results are compared with that obtained by the other researchers. It is found that the yield ratio varies with the alloy composition, and is related to the disorder surface layer formed by argon ion bombardment. The yield ratio S_(Ag)/S_(Pd) of the Pd dilute alloy (X_(Pd)=0.32 at.-%) is much larger than that of the others.

In accordance with the idea of generalized phase rule, we have studied the necessary condition of existence of predominance area of phase diagram, in which the number of required message input has been reduced to minimum, and set up the computer program for automatically drawing and calculation. In this program system, it contains the following 7 functions: (1) automatically balance the stoichiometric constants of all possible reactions, (2) carry out the Gibb,s free energy calculation of all possible reactions, (3) automatically cancel out the non-existence phase in the designated condition, (4) calculate out all of the locations of 3 phase intersections, 2phase cross lines, (5) find out the phase name, (6) find out the temperature profiles to be interested in, and (7) select the appropriate parameters. This program system has been used in the field of pyrometaUugy for explaining how to select the best operating condition.

A brief review of the recent works by the authors is given on the physical properties of the 4%Si-Fe, the mechanical properties of the hot rolled sheet, the cold-rolled and annealed texture as well as the secondary recrystallization and the magnetic properties.