Titanium was recovered from red mud by acid leaching with sulfuric acid,hydrochloric acid or nitric acid as the leaching agent.The effects were investigated of kind and concentration of leaching agents,liquid to solid ratio,leaching temperature and reaction time on titanium recovery.The results show that sulfuric acid is more appropriate as the leaching agent.The leaching rate of titanium reaches 90% under the conditions of sulfuric acid concentration 40%,leaching temperature 100℃,liquid to solid ratio 6∶1and reaction time 60 min.Brookite and calcite disappear,perovskite,hematite and cancrinite decrease and anhydrite forms during acid leaching.Dissolution reaction of perovskite and brookite in sulfuric acid results in titanium recovery from red mud.

WC powder was prepared with mechanical activation assisted molten salt method,where W powder and active C powder were mechanically activated at first and then reacted in molten salt.And the reaction mechanism of WC formation in molten salt was discussed.The research shows that W2 C and WC powders can be successfully prepared in 1 000℃ molten salt.Both the increased reaction temperature and activation time contribute to the formation of W2 C.W2C would gradually transform into WC with the further prolonged time of heat preservation.

W-20%Cu composite material was successfully prepared by SPS with W-20%Cu(mass fraction)composite powders as raw materials obtained by hydrothermal synthesis-coreduction,and its microstructure and properties were analyzed and studied.The results show that with the increase of sintering temperature and heat preservation time,microstructure distribution of W and Cu is more uniform with less porosity,and density,hardness and electrical conductivity of W-20%Cu composite material are subsequently increased.Under the conditions of sintering temperature 950 ℃ and heat preservation time 5min,the density,hardness and electrical conductivity of W-20%Cu composite material are 98.9%,HV222.8and 21.7 MS/m,respectively.

The heavy tungsten alloy of 93W-4.55Ni-1.95Fe-0.5Co was prepared by direct liquid phase sintering process and two-stage sintering process(i.e.solid-state sintering at first and then liquid phase sintering)and its microstructure and properties were investigated.The results show that sintering distortion of the alloy can be controlled by using two-stage sintering process,the distribution of tungsten grain and binder phase is more homogeneous,and the mechanical properties especially ductility and toughness are improved to a great extent.

The principle of X-ray diffraction(XRD)and its application in tungsten powder metallurgy are introduced.Combined with the authors' research on WC-Co nanocomposite powder,the application of XRD technique in preparation of WC-Co nanocomposite powder is emphatically introduced,including qualitative phase analysis,grain size determination and lattice parameter determination.Using soluble cobalt salt,ammonium metatungstate(AMT)and organic carbon source as main raw materials,WC-Co nanocomposite powder was prepared by spray conversion and continuous low-temperature reduction carbonization and the samples were analyzed by XRD during preparation.The results show that the composite powder only having the two phases of WC and Co can be prepared by spray conversion and continuous low-temperature reduction carbonization,W is completely carbonized,the grain size of WC is about 60 nm,and Co phase exists with face-centered cubic structure.

The precursor of fluorine-containing cerium-based rare earth polishing powder was obtained by fluoridization of cerium-based rare earth carbonate added with hydrofluoric acid,and then it was roasted at high temperature and ground and graded to prepare fluorine-containing cerium-based rare earth polishing powder.The effects were investigated of two fluoridization methods on phase structure,particle size and distribution and polishing performance of fluorine-containing cerium-based rare earth polishing powder.The results show that fluoridization method has no obvious effect on polishing performance of cerium-based rare earth polishing powder.However,the particle size is significantly reduced of the polishing power and its precursor prepared by fluoridization with hydrofluoric acid at first and then precipitation with ammonium bicarbonate,and their particle size distribution is narrower.

NdFeB permanent magnet was prepared by rapid solidification strip casting and hydrogenation crushing,and its microstructure and properties were characterized by optical microscopy,scanning electron microscopy and AMT—4magnetic property tester.Investigation was made of the effect of sintering temperature on the microstructure and properties of the magnet.The results show that with sintering temperature increasing,the density of the sintered magnet increases,and its remanence,coercivity and maximum magnetic energy product increase at first and then decrease.The reason is that the major crystalline phase grains grow up and the neodymium-rich phase distribution is more homogeneous with sintering temperature increasing.However,when the sintering temperature reaches a certain value,the magnet microstructure is inhomogeneous and the neodymium-rich phase agglomerates.

LaFe11.1-xCrxCo0.8Si1.1B0.25 and LaFe11.1-xTixCo0.8Si1.1B0.25 series alloys were prepared by adding a small amount of Cr and Ti elements into LaFeCoSi-based alloy,and their magnetocaloric effects were measured using directly measuring instrument at 1.5T magnetic field.The experimental results show that both Cr addition and Ti addition have influence on Curie temperature and magnetocaloric effect of the serie alloy.The properties of the material can be adjusted to some extent taking advantage of these alloying elements.

Hot compression was carried out on a Gleeble—3500thermal simulation testing machine of Ti-55511 alloy with the initial microstructure characteristics of pureβ,globularα,thick lamellarαand thin lamellarα,respectively.Plastic flow behavior of the alloy was studied at 700~800 ℃ deformation temperature and 10-3~10-1 s-1 strain rate.Investigation was made of the effects of initial microstructure characteristics on alloy thermoplastic deformation behavior.The results indicate that the flow stress of all the alloys with different initial microstructure increases with strain rate increasing and formation temperature decreasing.The order of deformation difficulty is pureβalloy>thick lamellarαalloy>thin lamellarαalloy>globularαalloy.The instability zones are mainly distributed at low temperature and high strain rate zones in the processing map.With the increase of deformation strain,instability area of globularαalloy gradually decreases while the instability areas of all the other alloys increase at first and then decrease.The differences of alloy deformation behavior are related to the microstructure evolution during deformation such asβ→αphase transformation,plastic instability of lamellarαphase,fragmentation and globalization ofαphase,shearing deformation and local plastic flow.

AgSnO2(8)In2O3(4)electrical contact material was prepared by powder metallurgy,alloy powder pre-oxidation and pressurized internal oxidation,respectively.The influences were studied of different preparation processes on the microstructure and properties of the AgSnO2In2O3 electrical contact material.The results show that the AgSnO2In2O3 material prepared by pressurized internal oxidation has the most uniform microstructure,highest relative density and maximum microhardness,while the material prepared by powder metallurgy has the highest electric conductivity.Under the electrical contact condition of DC resistive load,AgSnO2In2O3 material prepared by pressurized internal oxidation has the best arc erosion resistance with the lowest weight loss and minimum arc erosion area of contact surface.