The processes of the precipitation and growth of δ'-phase(Al3Li) in an 8090 Al-Li alloy(Al-2.45Li-1.21 Cu-1.20Mg-0.15Zr) under different heat-treatments have been studied by TEM and image analyses.The results show that the growth of δ'-phase,the main strenthening phase in the alloy,consists of rapid and slow stages during aging at 160℃.The relationship between r3(r being the radius of δ'-particle) and aging time is not linear.As an analytical result,the value of k in LSW model may decrease as the vacancy concentration reduces.

Rene'95 superalloy with hight density(>95% of theoretical value) and necklace microstructure has been obtained by liquid phase sintering and isothermal forging of the atomized alloy powders.This combined method of powder metallurgy can avoid the carbide precipitation at particle boundaries.which appeared generally during isostatic pressing.

A recently modified continuum model has been adopted to investigate the solidifying behaviour of cast ingot.Emphasis has been laid on the interaction among the fluid flow,temperature distribution and solute field.The effects of two kinds of driving forces,T/x and w/x,have also been analysed.

A computer program for simulation and prediction of formation of inclusions in steels during solidification was developed.Microsegregation of solutes during solidification of steels is calculated based on CLYNE-KURTZ's model.By use of this program the composition of solutes and formation of RE inclusions in liquid steels can be simulated at any time.The predicted composition of inclusions accords with the experimental result.

In this paper,four aluminium alloy powders were prepared in a two-stage atomization equipment.The particle sizes, morphology and microstructure were examined.The cooling rate of powder was also determined.The average size of particles by two-stage atomization is double finer than that by gas atomization,and the average cooling rate is ten times as high as that by gas atomization.The microstructure of particle in Al-Si alloy mainly consists of block supersaturation solid solutions with different contents of silicon.

The effects of boron on the microstructure,mechanical properties,corrosion and corrosive wear resistance of aluminium bronzes were investigated systematically.The results show that the addition of boron can fine the grain size,increase the strength and hardness of aluminium bronze without greatly affecting its plasticity,the selective corrosion and corrosive wear resistance were also improved.The mechanism of boron in aluminium bronze was discussed.

The observations of the crack morpholgies on the side faces and fracture surfaces of the fracture toughness specimens and the TEM analyses of deformed structure around crack were conducted for the FFL microstructure which was obtained from the cast Ti-46.5 Al-2.5V-1.0Cr-0.2Ni(atomic fraction,%) alloy by a designed multiple heat treatment.The fracture characterizations of the FFL microstructure are similar to that of the FL microstructures.The functions of each shear ligment and total deformed volume accompanying the crack in the FFL microstructure were much smaller due to the significant decrease of the lamellar colony size.This led to a descent of fracture toughness of the FFL microstructure compared to the general FL microstructure.

Fatigue tests were performed on specimens P(horizontal grain boundary) and V(vertical grain boundary) which were cut from the same aluminum bicrystal but their orientations are vertical to each other.It is shown that there are remarkable differences in the deformation behaviour and failure mechanisms between specimens P and V.In specimen P,more than two secondary slip systems are activated and primary slip band is repressed in the grain boundary effect zone,it is found that microcracks initiate along grain boundary where deformation is more severe than that in slip band and not uniform. In specimen V,however,the deformation at grain boundary is very small,it can be seen that damage occur only in primary slip bands which reach grain boundary.By considering the same grain boundary structures in specimens P and V,it seems that the effects of grain boundary structure(e.g.∑ value) on the deformation of grain boundary itself are less important.In addition,contrast experiments were done,and it is found that the fatigue cracks growing along the oblique grain boundary and the grain boundary with greater orientation difference between neighboring grains can be obviously accelerated.

The fatigue crack propagation rates of ZG42CrMo and its porosity area were measured.The process of fatigue crack growth in porosity area was observed by using metallographic tracing method.Dislocation and slip at the tip of fatigue crack have been studied by using TEM.The morphologies of porosities and microcracks together with sulphide on the surface of porosities were researched by using EPM.Two effects of porosities which make crack deflection and catch crack on fatigue crack growth have been discussed.Possible mechanism of microcrack initiation has been analysed.

The critical void-growth ratio,Rc/Ro,of steel BHW60,steel 20 or steel 45 was measured quantitatively under SEM,and the measured positions are at the core of fracture surface of cylindrical tensile specimens.The ductile-brittle transitions due to both temperature and torsional prestrain were discussed by means of the micoscopic parameter ln(Rc/Ro).The concepts of both nil-ductility trasition stress triaxiality Tσ,ND and nil-brittility transition stress triaxiality Tσ,NB were proposed and the coupled effect of temrepature and stress states on the ductile-brittle transition was analyzed

Thermal behaviours of Co/C multilayers prepared by a dual-facing-target sputtering system were studied by using X-ray diffraction,transmission electron microscopy,Raman spectroscopy,and X-ray photoelectron spectroscopy.The changes observed in the annealed Co/C multilayers include an expansion of modulation period,crystallization in the Co layers,changes of reflectivity at grazing incidence and Co-C compound formation.Below annealing temperature of 400℃,the expansion in modulation period is mainly due to the graphitization of the amorphous carbon layers,and the enhancement of the reflectance is dominantly caused by Co-C separation that is interpreted as positive enthalpy of Co-C mixing.By 500℃,the crystallization and agglomeration of Co layers induce an enormous period expansion and a serious decrease in reflectivity.A small amount of carbide is found to form at this temperature as occurred in some other annealed metal-carbon multilayer systems.

The phase interfacial transition layer in Ti(C,N)-based cermet has been proved systematically by using TEM and EDAX.Experimental results show that there exist obviously a surrounding structure at the edge of carbonitride phase in Ti(C,N)-based cermet,it is a transitional phase.Ti(C,N)/Ni phase interface has no constant orientation relationship.W and Mo are basically concentrated in interface and there is a composition gradient of Ti,Ni,W and Mo in phase interface.HREM observation of interface reveals that in phase interface of Ti(C,N)-based cermet,the transitional layer has width of 8-10 nm and nanocrystalline structure.

The slag structure and mechanism of multipeaks in reduction rate during smelting reduction of V-Ti containing magnetite were systematically analysed.There are three peaks of reduction rate without iron bath and two peaks with iron bath.The first peak is formed by reduction of magnetite,the second peak by reduction of ferric oxides to iron and the third mainly by reduction of titanium oxide to metallic titanium or TiC and TiN.

A detailed microstructure analysis of Ag1-xCux(0.05≤x≤0.40) nanocrystalline alloys synthesized by an inert gas condensation method was reported.Results show that homogeneous Ag-Cu nanocrystalline alloys can be prepared, and the grains of the two components are about equal in size,no preferred orientation is detectable.However,for larger Cu pontents up to 40%(atomic fraction),the segregation of Cu particles was observed in some of the samples.No appreciable Ag-Cu metastable phase was detected by electron diffraction technique and HREM observation,only a two-phase equilibrium structure was observed.

The contribution of dilated lattice constant of nanocrystal to the resistivity is investigated by using the Landauer formula.The relationship between Landauer resistivity and crystal dilation is given.Numerical calculation shows that the resistivity is increasing nonlinearly as the dilation growing.

Nanocrystalline titania particles were prepared by using precursor method from titanium tetrachloride.The microstructure was determined by using DTA-TG,XRD,TEM and Q-900 analyses.The results show that the spherical nanocrystal with rutile structure has an avarage diameter of 8.5 nm,good dispersity and purity.It's size distribution is from 5.0 nm to 15.0 nm.

TiC-Al composites were prepared from powders of Ti,C and Al by means of thermal explosion technique.The effects of heating rate and aluminium content on the thermal explosion process,phase composition and microstructure of the reaction products have been studied.By differential thermal analysis,X-ray diffraction and scanning electron microscopy,it is shown that the explosive reaction in the Ti-C-Al system proceeds in such a way that aluminium initially reacts with titanium to form Ti-Al compounds with heat evolution,and then the reaction between titanium and carbon,and the decomposition of Ti-Al compounds to titanium and aluminium are subsequently followed.The certain heating rate and aluminium content are needed if the thermal explosion occurs at low temperature in Ti-C-Al system.As mass fration of aluminium was increased over the range of 10% to 50%,the grain size of TiC decreased approximately from 5.0μm to 0.5μm.

The process that Ni3Al/TiC composites were synthesized by the thermal explosion mode of self-propagating high-temperature synthesis(SHS) from Ti-C-Ni-Al system was studied.The occurrence of thermal explosion depends on two factors,one is the heating rate,and the other the heat of the system(that is,Ni3Al content).The density of the products varies with Ni3Al content,and a maximum value of density appears at 40% Ni3Al.The effect of Ni3Al content on the microstructure of the products was characterized by means of SEM technique.

Combining the advantages of ingot metallurgy,rapid solidification technology and in situ processed composites,a kind of innovative in situ Al-TiC composite has been successfully made with a series of research on its microstructure and properties.The ingot metallurgy microstructures exhibited that the accumulated TiC particulate phase with a volume fraction of 14.5% and sizes of 0.2-1.0μm segregated generally at the α-Al grain boundaries.After rapid solidification and thermal extrussion,the microstructures comprise uniform fine-scale dispersions of TiC phase particles(the volume fraction slightly reduced as 13.5%) with sizes of 40-80 nm in a supersaturated α-Al matrix of 0.30-0.80 μm grain sizes.The rapidly solidified in situ Al-TiC composite exhibited high Young's modulus and substantial improvements in room and elevated temperature tensile properties.

Elevated temperature tensile behaviour and interfaces in NiAl-TiC in situ composites fabricated by the HPES technique were investigated by using SEM and HREM.The results show that the tensile strength of NiAl at high temperature is strengthened considerably by the TiC particulates.Interlacing interfaces existed between NiAl and TiC may contribute to the enhancement of strength of the NiAl-TiC composites.