ZHANG Sanhong;HE Xinlai;CHU Youyi;KE Jun T. Ko University of Science and Technology Beijing,Department of Materials Physics,University of Science and Technology Beijing,Beijing 100083)

The crystal habit, crystalline structure, surface condition and composition ofthe ultrafine Al particles, prepared by an inert gas evaporation method, were studied in detailby means of high resolution transmission electron microscope, X-ray diffraction and X-rayphoto-electron spectrum. The particles are of clear crystal habits, single crystal in a large ma-jority and fcc crystalline structure with α_0=0.405 nm. A protective layer of amorphousAl_2O_3, 2 nm in average thickness, against oxidizing further was found around the particles. Itis believed that the ultrafine Al particles prepared by the inert gas evaporation method arevery stable in atmosphere.

Many compression and tension tests showed that the room temperatureductility of boron-free microalloying Ni_3Al may markedly improved by a moderate additionof Zr. An additive of Zr in the stiochiometric Ni_3Al, even slightly enriched Al, may be tough-ened and improved fairly on brittleness at 400--600℃. This behaves much better if Zr addedtogether with B. However, the high temperature ductility of Ni_3Al alloy containing Cr may besignificantly increased by Zr, which is slightly segregated along grain boundary. Thus, thetoughening mechanism by Zr seems to be different from that by B.

Effect of various contents of La additive in Fe-P-N alloy on theirSnoek-Ke-Koster (SKK) internal friction peak was found to be related to atomic concentra-tion ratio, C_(La)/ C_P. La may intensify obviously the damping of SKK if C_(La)/ C_P≥2.6, and af-fect no more if C_(La)/ C_P=0.27 and P in supersatureation.

The dependence of nodularization of graphite upon Ce content in RE nodularcast iron, prepared by directional solidification, has been investigated by electrolytic extrac-tion-radioisotope assay analysis of Ce in each phase of the iron together with measurement ofnodulized graphite. Results show that the Ce occurs mainly as alloyed form. In the graphitephase, the Ce content is believed to be characterization of nodularization. The graphite wouldcompletely nodulized only the Ce is over a certain content in graphite phase.

Using 3-dimensional orientation distribution function, study was made of theeffect of non-equilibrium segregation of P on the orientation variation in cold rolled Fe-P al-loy during annealing under analytical electron microscope. P is found to segregatepreferrentially on the {110} slip plane. The non-equilibriously sgregated P forms a structurewith repeat cycle a=1.582 nm over 450℃. The fiber texture may vary in decrease of <001>// ND and increase of <001>// ND, and transfer from {111} <110> to {111} <143> withtemperature raising during alloy recovery. After recrystallization, direction {111} <143>changes into {111} <112>. A proposed model about the formation of recrystallization tex-ture was fairly explained by structure of P non-equilibrium segregation.

Relationship among deformation history, fracture process and stress distribu-tion of granular bainite has been investigated. The main process of fracture of granularbainite is forming, growing and coalescence of the microvoids. Even though the microcrackshave formed at the earlier stage of deformation, they are not fateful for fracture because in thesuccessive deformation stage the microcracks change their orientation and parallel to the ten-sile axis. The strain hardening rate of granular bainite has a minimal value during thedeformation process. Before and after the strain of the minimal value, the material showsdifferent stress distribution and microfracture mechanism.

Fatigue crack growth rates of 8090 type Al-Li alloy in air were found to bestrongly dependent upon the aging conditions. The naturally aged and underaged specimensshowed the highest resistance to the fatigue crack propagation. The fatigue crack growth re-sistance of the overaged specimen is the lowest and that of the peakaged specimen in between.As compared to air, 3.5%NaCl solution did not change the effect of aging conditions on thefatigue crack growth, but caused a decrease of the resistance to the fatigue crack growth un-der the same aging condition. Both short cracks from notch and physically short cracksshowed much higher rates of fatigue crack propagation in comparison with long cracks underthe same aging condition and stress intensity level. The growth behavior of the short crackdepends on its type. The growth rate of short crack from notch decreases first to a minimumand then increases with increasing AK. However, the physically short crack grows at aprogressively increasing rate. The effects of aging conditions were explained in terms of theslip planarity of dislocations and the cyclic slip reversibility. The observed short crack behav-ior was considered to be dependent on the crack closure and the local plasticity near the crack

A composite method of solution for contact stresses on roller was suggested bythe combination of similitude principle, photoelastic method, Hertz's contact theoty andnumerical calculation. Thus, not only the reasonable distribution of axial contact pressureon roller of limited Iength, but also the three-dimensional solution of stress in the contactpost may be obtained. Obeservation on the prachcal damaged roller is in agreement with theresult after contact stress analysis of such a working roller.

Equilibrium constant, K_T, and free energy of formation △G, of the reaction: Ga_(As)As_(Ga)+(V_(Ga))_2~-+e~-=As_(Ga)V_(Ga)~-+Ga_(As)V_(Ga)~-were deduced as: K_T=(1.088×10~81.090×10~(11)·1/ T)~2 AG°=-2RTln(1.088×10~8-1.090×10~(11)·1/ T) These seem to be applicable into practice under certain conditions.

Two surfaces corresponding to LaCl_3 and α-solid solution (MgCl_2, LiCl)respectively, and one secondary crystallization curve with a minimum M at 63.8wt-%LaCl_3, 2.0wt-%MgCl_2, 34.2 wt-%LiCl; 492℃ were found by means of DTA. Incombination with liquidus determination, an approach was also made to the alteration inLnCl_3-MgCl_2-LiCl system, where Ln denotes La, Ce, Pr or Nd.

An investigation was carried out of the effect of Y addition upon the internalstress of Al_2O_3 scale formed during oxidation of sputtering coating on Co-30Cr-6Al alloyand the growth stress of oxidized film on Fe-23Cr-5Al alloy heating up to 900℃ in air, us-ing a specially designed deflection method from thin strip specimen with coatings, ion-im-planted Y on one face and oxidized onto both faces. Results indicate that Y may decrease theinternal stress of oxide scale on 2×10~(17)Y~+/ cm~2 implanted Co-30Cr-6Al coating, and in-crease one on 2×10~(16)Y~+/ cm~2 implanted Fe-23Cr-5Al alloy. This seems due to promotingor not by Y to the plastic deformation of oxide scale. In addition, at the initial oxidationstage, the change of growth stress of oxide scale formed on Y-implanted Co-30Cr-6Al coat-ing may be related to the influence of Y on oxidation process of the coating.

Studies were carried out of the effect of mechanical parameters on theinteraction between stress corrosion cracking and corrosion fatigue, as well as of the featureof stress corrosion fatigue (SCF) on crack growth rate and fracture surface of 0Cr18Ni9Tisteel in boiling MgCl_2 solution. Any parameter, that increased the strain rate at crack tip,tends to promote the change of SCF from transgranular to intergranular mode.

A set of absorption curves was priorly prepared on transparent films to fit thebackground and peak intensities in continuous scanning X-ray stress measurement. It may bebetter to correct both background and absorption of pure diffraction intensity. Experimentalresults revealed this to be a reliable correction method.

Investigation was made of the sputtering rate in glow discharge lamp with re-lation to constituent of 25 different specimens of 6 binary systems, namely, Cr-Fe, Bi-Sb,Cu-Zn, Ag-Cu, Al-Zn and Cd-Sn, by measuring mass loss after each sputtering under con-stant Ar pressure and voltage applied. The correlation, in general, between sputtering rate andconcentration of constituent of these non-intermetallic binary alloys obeys the hyperbolic lawunder steady state, yet may be approximately regarded as linear only on certain special condi-tion if the two components of the alloys with similar sputtering rates.

The enthalpies of mixing for the PbCl_2-NaCl-BaCl_2 ternary molten salt mix-tures have been measured along four iso-α_(PbCl_2) lines by using a SETARAM calorimeter at873 K. The results show that the molar enthalpy of mixing between iso-α(PbCl_2) liquid binarysubsystems PbCl_2-NaCl and PbCl_2-BaCl_2 is near zero, i. e., approximately fitting the partialideal solution model.

Superior superplasticity was revealed in a warm-rolled Al-8Mg-0.2Zr alloy at temperatureeven 325℃. Elongation up to 400% may be obtained under tension at constant strain rate 1×10~(-3)s~(-1), and ahigher elongation as high as 630% may be reached by two-stage strain rate.