Retained austenite exists in alloy steels both continuously quenched and isothermally quenched, so its content relates to the austenitic stabilization. The article focuses on the investigation for the austenitic stabilization in isothermally quenched microstructures from duplex phase (martensite--M, bainite--B) temperature region. Within a certain isothermal time, the relationship of the amount of retained austenite AR vs isothermal temperature is a saddle--like curve, and the valley value for testing steel is less than that of continuous quenching with a same cooling medium, which proves that isothermal soak does not increase retained austenitic quantity on certain condition. By adjusting the content ratios of AR/M and AR/B on the saddle--like curve, an isothermal quenching of the less deformation or a meta-bainitic isothermal quenching with strength--toughness optimized combination can be achieved. Austenitic stabilization is the synthetic effect of thermal, chemical, phase induced and macro--thermal stress stabilized mechanisms. The martensite critical point Mc has not the special physical meaning.

The effects of Si on the martensitic transformation and magnetic transition of Co41Ni32Al27-xSix alloys were investigated by optical micrography, DSC and VSM methods. The structure type of martensitic phase was determined by X--ray diffraction. Martensitic transformation temperatures of Co41Ni32Al27 alloys are obviously elevated by the substitute of Si for Al element, the addition of 1% Si can increase the martensitic transformation temperature by about 50 K. Curie points are also increased with increasing of Si content, 1% Si can increase the Curie temperature by 10 K. Martensites are all of ordered L10structure, but the unit cell volumes are decreased with increasing Si content. The reason for above results were discussed.

The influence of high intensity magnetic field on the solidified structure and behavior of Bi--6%Mn alloy has been investigated experimentally. The morphology of primary MnBi phase in the alloy cooled to 360℃ from melt and hemi--melt above Curie temperature at 10 T magnetic field was blade-like and its short axis is the easy magnetization. Under high intensity magnetic field, the easy magnetization axis turned to the direction of magnetic field and aggregated along the direction of magnetic field, and finally formed lath--like structure. The solidified microstructure of Bi--Mn alloy under magnetic field was discussed on the base of magnetization and crystal growth theory.

The Ag--Ti diffusion couples were prepared by small pure silver plate closely packed in pure titanium powder and annealed at 980, 1100 and 1200 ℃ respectively. The phase equilibrium relationship and the equilibrium composition of conjugate phases in Ag--Ti system were determined by means of metallographic microscope and electron probe microanalysis. Especially for the liquid phase the B(Ti) phase and the intermediated phase (TiAg). The experimental results of the present work were compared with the assessed data of the anailable literature.

The microscopic phase--field approach was used in modeling the early precipitation process of Ni75AlxV25-x alloy with lower Al concentration on an atomic scale through the simulation of atomic pictures, calculation of order parameter profiles and change of volume fraction of the ordered phases. The results show that ordered phases precipitated and formed a pseudobinary system; precipitated earlier than g phase by a congruent ordering + spinodal decomposition (CO+SD) mechanism and thus produced a nonstoicheometric ordered phase, then the nonstoicheometric g phase precipitated by a non--classical nucleation and growth (NCNG) mechanism at the boundaries of phases, meanwhile, both of them transformed to stoicheometric ordered phases. With the increase of Al composition, the congruent ordering process of phase becomes more slow, and g phase precipitation becomes earlier, the occupation percentage of gincreased and that of phase decreased.

Grain boundary hardening and slip transmission across grain boundary are two important aspects in deformation of materials. Using depth--sensing indentation, a pop--in phenomenon induced by grain boundaries has been observed in polycrystalline niobium. This phenomenon is about a sudden displacement jump observed near a grain boundary segment at a larger force than the initial elasto--plastic pop--in, which is observed not to be affected by grain boundary. The experimental results show that this pop--in effect has a close relationship with misorientations of the grain boundary. Further studies found that no evident change of grain boundary hardness was observed even though there existed grain boundary pop--in.

Propagating of unloaded indentation crack in a PZT--5H ferroelectric ceramics with various poling states under single or combined action of mechanical and electric loading has been investigated. The results show that the stress intensity factor induced by the residual stress of an unloaded indentation crack is approximately equal to the fracture toughness. The applied stress or/and electric field, positive and negative, can cause propagating of the indentation crack, and the combined effect of mechanical and electric loadings corresponds to applying an efficient stress.

BT18Y titanium alloy was treated with several groups of heat treatment. After solutionized frectment at phase field, metalloscopy, transmission electron Microscope (TEM) and scanning electron microscopy (SEM) were employed to observe the microstructures. It was found that the continuous grain boundary (GB) phase is spheroidizes and the edges of some intragranular primarylaths show “forked” morphology. The ultimate reason of the spheroidization of GB is the diffusion of solute atoms due to the difference of solute concentration, which results from the different interfacial curvatures at different sites. The joint of two GB lamellas also gives some contribution to the spheroidization of GB . The “forked” morphology at the edge of primary lath results from different interfacial structures and energies between phase and different parts oflath. The incoherent interface between phase and the edge of lath has high interfacial energy and moves easily. When the alloy is solutionized at phase field, phase trends to grow into lath and forms lath, which results the “forked” morphology of primary lath.

Near threshold fatigue crack growth tests were conducted under torsion on circumferentially pre--cracked round bars of a stainless steel. The crack growth rate was decreased with crack extension because of the sliding contact of the crack faces. The crack growth rate without the influence of crack surface contact was determined by extrapolating the relationship between the crack growth rate and the crack extension to the zero crack length. The applied stress intensity factor range is divided into two parts: one is the effective value responsible for crack growth and the other is the shielding value dissolved by crack surfaces contact. The fatigue limits for crack initiation and fracture were predicted and the predicted values agreed well with the experimental results.

The temporal and spatial behaviors of the PLC (Portevin--Le Chatlier) effect in Al--Cu alloy are systemically investigated and analyzed. Under different applied strain rates, three types of serrated stress-time curves are obtained respectively. And the similarities and differences of them are compared and interpreted qualitatively. Correspondingly, the spatial propagating characteristics of the three types of PLC deformation bands are observed and analyzed. The evolutions of the propagating velocity for type A and B bands are discussed with respect to different tensile strains in the 3mm thick specimens. At the same tensile strain, the power law relationship between band propagating velocity and applied strain rate is also obtained. Contrasting the serrated stress-time curves with the position--time plots, the relationship between the macroscopic spatiotemporal behaviors is compared for the PLC effect. The influence of specimen thickness to the spatial correlation of PLC deformation bands is also discussed.

Cr--Al(Cr)2O3 cermets have been successfully produced by combustion synthesis, through changing the composition of reaction system and controlling the solidification process. The microstructures of the cermets were characterized by dispersive sub--micron scale Cr particles in ceramic matrix. The effects of polymer addition and system composition on the microstructure of the cermets and combustion synthesis procedure were investigated. The results show that the igniting temperature and time of Al--Cr2O3--Al2O3 system decrease evidently with polymer addition. Also, the polymer addition could make Cr particles more uniformly distribute in the ceramic matrix. By adding the diluent Al2O3 and excessive Cr2O3, the size of Cr particles could be decreased, and the matrix of the cermets are changed from pure Al2O3 to Al2O3 and (Al, Cr)2O3 mixture. The densification of Cr--Al(Cr)2O3 cermets is achieved by applying a lower pressure on the synthesized melt.

Cu47Zr11Ti34Ni8)100-xCrx(x=0, 0.5 and 1.0) bulk metallic glasses (BMGs) were obtained by water--cooled copper mold casting. The effect of Cr micro--addition on the glass--forming ability (GFA) of the alloys was investigated by means of XRD, DSC and DTA. It was found that Cr micro--addition can enhance the GFA. Electrochemical measurements were carried out in 1 mol/L HCl, 3% NaCl and 6 mol/L KOH aqueous solutions by potentiadynamic polarization method at room temperature. It is shown that all the BMGs exhibited spontaneous passivation in the above electrolytes, and with the increase of Cr content, the passive zone remarkably increased and the passive current density decreased, implying better corrosion resistance of Cu-based BMGs with higher Cr content. The present results also demonstrated that the corrosion resistance of Cu--based BMGs with Cr micro--addition is much better than that of the stainless steel.

The microstructures, phase transformations and wetting behaviors of the Sn--Zn--Bi solders were investigated. The results show that adding 2\%---10\% Bi(mass fraction) to Sn--9Zn binary alloy, the primary Zn rich phase appears from the melts firstly on cooling, which results an increase of the pasty ranges. The crystallizing points decrease with addition of Bi, indicating a decrease of the melting points. Fixing Bi concentration, reduction of Zn decreases the pasty ranges, and the melting points keep stable. Addition of Bi improves the wettabilities, because the wetting areas on Cu substrates of the alloys are increased, and the wetting times are shorten. The diffusion of Zn into Cu at the solder/Cu interface is accelerated by increaseing Zn concentration, which decreases the solder/Cu interfacial energy. With addition of Zn, the wetting areas on Cu substrates of the Sn--Zn--Bi solders increase and the wetting forces enhance. But the diffusion needs a period of time, which means a prolonged wetting time. Therefore, Zn concentration must be controlled in order to obtain a good matching between the spreading area and the wetting time.

Al2O3 particles, in situ decomposed from Al2(SO4)3, reinforced Al--4Mg matrix composites were made through stir casting. Al2O3/Al interface in the Al--4Mg matrix composites was studied by transmission electron microscopy (TEM). The measurements of crystallographic orientation relationship between Al2O3 and Al at Al2O3/Al interface show that no fixed and unique orientation relationship existed, though the following preferential ones were observed: ：( )Al2O3//(111) Al，[ ]Al2O3//[ ] Al，[ ]Al2O3//[ ] Al。

The connection behavior and joint microstructure of capacitor discharge welding for melt--spun Cu--20%Sn alloy foils are investigated by using a micro--type capacitor discharge welding machine. The micro joint consists of nugget zone, semi--melt zone and heat affect zone. The rapid solidification microstructure characterized mainly by fine b--Cu5.6Sn equiaxed grains are produced in the nugget. The thickness of semi--melt zone is only 2.0---3.0um and there is no obvious change of microstructure in heat--affected zone. Under the electrode pressure and electromagnetic force, the liquid phase flow occurs in undercooled nugget, which is symmetrical about the electrode axis and connection interface and results in the formation of curving streamline. The porosity is the main welding defect produced during welding. With the increase of electrode pressure pm, the radius of porosity sharply decreases. If the electrode pressure is more than 1.0 MPa, this decrease tendency becomes smooth. The liquid phase flow promotes the collision, coalescence and movement of bubbles, resulting in that porosities distribute along the periphery of nugget.

The apparent viscosities of semi--solid AlSi6Mg2 alloy at steady state were investigated using a Couette type viscometer. The results show that the apparent viscosities of semi--solid AlSi6Mg2 alloy at steady state increase with increasing solid fraction, but decline with increasing shearing rate. When the solid fraction reaches a critical value, the apparent viscosities increase rapidly and with the increase in shearing rate, the critical fraction value becomes bigger. Based on the experimental results, an empirical equation that shows the effect of solid fraction and shearing rate on the apparent viscosities was built as the following,a =78.6 exp(6.17 fs)－1.36。

IrO2--Ta2O5 oxide anode was prepared by coating oxide on titanium substrate which has been pretreated by sandblast and oxalic acid etching. ESEM, polarization curve and EIS indicated that the corrosion rate of the substrate and the loading of the oxide coating (i.e. Ir content) increase with etching time at the initial stage and then decrease. The oxide coating on the substrate pretreated by suitable etching pretreatment is of a uniform and compact surface which has large electrochemical active surface area, fine electrocatalytic activity for oxygen evolution and high stability.

Electrochemical impedance spectroscopy (EIS) was used to study the influences of the binder, pigment shape and the coating thickness on the corrosion prevention performance of the zinc--rich coatings (ZRC). There are two time constants for these coatings, the first one is attributed to the contact impedances between the different zinc particles and the second one is related to the charge transfer resistance of the Zn dissolution process. Furthermore, the EIS data of ZRC were interpreted according to equivalent circuit models. The corresponding parameters were derived to assess the coating deterioration with time and the performance between zinc dust primers and zinc flake primers were compared. The results showed that the zinc flake reduced the cathodic protection period of the ZRC and rapidly produced a little compact barrier.

Berkovich nanoindentation tests with different loading rates have been performed on the Sn--3.0Ag--0.5Cu bulk solder and Sn--4.0Ag--0.5Cu lead--free ball grid array (BGA) solder joint. The load--depth curves are rate dependent. The Young's modulus of bulk solder and BGA joint obtained from load--depth curves with Oliver--Pharr method are 9.3 and 20 GPa respectively. The creep rate sensitivity of bulk solder and BGA joint obtained from curves with the concept of “work of indentation” are 0.1111 and 0.0574 respectively. The mechanical properties of Sn--Ag--Cu lead-free solder are typically size dependent.

The Trans--Varestraint test was modeled with finite element method (FEM) and the local strains in the trail of weld molten pool were obtained with different bending strains. The results show that there is a strain concentration in the train of weld molten pool during Trans--Varestraint testing and the calculated local strains thus modify the tested average strains, that is the material resistance to weld solidification cracks. Moreover, the calculated local strains agree well with the measured local strains got with the combination of high speed CCD camera and the Trans--Varestraint test. Furthermore, the driving force to the solidification crack of the stainless steel SUS310 was calculated and compared with the modified resistance so that the weld solidification crack was predicted, which agrees well with the experimental results. The results indicate that the weld solidification crack can be predicted with combination of Trans--Varestraint test and FEM.