In order to improve the leaching rate of zinc, indium and germanium in zinc oxide flue dust, a mechanically assisted ball milling and acid leaching process was proposed to treat zinc oxide flue dust.The effects of pellet-material ratio, end point acidity, reaction temperature, reaction time, stirring rate and oxidant on the leaching rate of zinc, indium and germanium were investigated.The results show that adopting the process of secondary acid leaching with mechanically assisted ball milling, the leaching rates of zinc, indium and germanium reach 93.35%,91.25% and 85.58%,respectively, under the conditions of liquid-solid ratio of 5∶1,ball-material ratio of 1∶3,reaction temperature of 85 ℃,reaction time of 2 h, end point aci-dity of 120 g/L,stirring rate of 800 r/min, and without oxidant.Compared with the original process, all the leaching rates are greatly improved, and the leaching effect is better.

WC-reinforced Ni-based coatings with different VC contents were generated in situ by laser cladding on the surface of H13 steel, and the role of VC inhibitor in refining WC grains and its effects on the hardness and wear resistance of the coatings were studied.The phase, morphology and composition distribution of the coatings were analyzed by XRD,SEM and EDS,respectively.The hardness of the coatings was measured by a microhardness tester, and the wear resistance of the coatings was tested with a friction and wear test machine.The results show that VC has a significant effect on inhibiting the growth of WC grains, and the inhibition effect is the best when the VC content is 10%.The hardness of the coatings with different VC contents is higher than that of the coatings without VC.The coating with 15% VC has the highest hardness.The wear resistance of 10%VC+(W+C)+Ni60 coating,(W+C)+Ni60 coating and Ni60 coating sequentially decreases.VC can hinder the precipitation mechanism of in-situ generated WC grains, resulting in grain refinement.The added VC may also deposit on WC grains, preventing their further growth.An appropriate amount of VC can significantly inhibit the growth of the WC reinforcement phase and improve the hardness and wear resistance of the coatings.

In order to further improve the oxidation resistance of Ti-20Mo alloy,the surface oxidation and microstructure evolution of Ti-20Mo superalloy used for electric power were studied at different thermal exposure temperatures.The results show that there are equiaxedαgrains and a large number of lamellarα+βeutectic microstructure in the original alloy.When the samples are exposed at 200℃and 400℃,their weight gain is less than 6mg.When the thermal exposure temperature is 600℃,the oxidation weight gain of the sample increases approximately linearly,and finally reaches 16.1mg.The increase of thermal expo-sure temperature can help the alloy to faster complete the recovery and recrystallization transformation process and achieve the purpose of fine grain strengthening.The equiaxedαcrystal grains and the lamellarα+βeutectic microstructure are formed in the thermally exposed alloys.With the increase of temperature,the grain size obviously increases and the grain distribution becomes more uniform.A large number of fine microstructures are precipitated in the grain boundary at 600℃.The microstructure of original Ti-20Mo alloy consists ofαphase and TiO₂ phase,and more TiO₂ phase is generated with the increase of thermal exposure temperature.When the thermal exposure temperature is 200℃or 400℃,TiO₂ is formed in the alloy oxide film.When the temperature rises to 600℃,Al₂O₃ is formed in the alloy oxide film.

Using sodium carbonate or sodium bicarbonate as precipitant,the yttrium chloride feed solution was precipitated at room temperature(5~35℃),and then yttrium oxide powder was prepared by calcination.The powder was characterized by laser particle size analyzer,scanning electron microscope and Hall flowmeter(funnel method).The effects of precipitant type,precipitant/yttrium chloride molar ratio and polymer dispersant(PVA)on the surface morphology,particle size distribution and bulk density of the formed yttrium oxide powder were studied,and the optimal process conditions were determined as follows:sodium carbonate as precipitant,Na₂CO₃/YCl₃ molar ratio≤1.5,and PVA mass fraction of 0.001%~0.01%.The obtained Y₂O₃powder under the above conditions has large and narrowly distributed particle size(D₅₀=20~100μm,(D₉₀-D₁₀)/(2D₅₀)<0.5),bulk density of 1.0~1.2g/cm³,good sphericity de-gree,excellent dispersibility and fluidity.The process is simple and easy to control and industrialize,with low cost and no pollution.

AC55-xY(x=0,0.5,1.0)magnesium alloys with different yttrium contents were prepared by semi-continuous water-cooled casting.The effects of yttrium addition on corrosion resistance and room-temperature mechanical properties of AC55-xY(x=0,0.5,1.0)magnesium alloy were studied by metallo-graphic microscope,X-ray diffractometer,scanning electron microscope,immersion corrosion test and elec-trochemical test.The results show that with the addition of the rare earth metal yttrium,the alloy grains are obviously refined,the eutectic phase changes from continuous structure to semi-continuous network structure,and the mechanical properties of the as-extruded alloy are greatly improved.Compared with AC55alloy,the tensile strength and yield strength of AC55-1.0Y alloy are increased by 19.2%and 17.2%,respectively.With the increase of yttrium content,the corrosion resistance of as-extruded AC55-xY magnesium alloys sequentially increases.The dense and stable corrosion product film formed during the corrosion process plays a vital role in improving the corrosion resistance of the alloy.

The effect of Ce on improving the thermoplasticity of copper-containing arsenic steel was investigated by Gleeble—3800 thermal/force simulation test machine.The results of thermoplastic curve analysis and fracture and microstructure observation show that adding 0.005 8% Ce can reduce the temperature range of the thermoplastic groove of copper-containing arsenic steel, and improve the thermoplasticity of the steel at 957~1 100 ℃ to a certain extent.The addition of 0.005 8%Ce can reduce the temperature to 1 000 ℃ at which the hot tensile fracture of copper-containing arsenic steel is completely transformed into dimple fracture, and at the same time, the temperature at which copper-containing arsenic steel enters the austenite single-phase region can be reduced to 800 ℃.There are no arsenious rare earth inclusions in the copper-containing arsenic steel with 0.005 8%Ce, while the solid solution Ce in the steel segregates prefe-rentially at the grain boundary, reducing the As content at the grain boundary, and thereby improving the thermoplasticity of copper-containing arsenic steel.

To better investigate the precipitation behavior of carbonitrides(MX)in Nb-V-Ti-N microalloyed structural steel,the Thermo-Calc software combined with TCFE8database was used to analyze the type,quantity,temperature and composition of the precipitated carbonitrides.And their morphology,composition,size and distribution were analyzed using FESEM,TEM and EDS.The results show that the MX precipitates in the steel are Ti-rich high-temperature precipitate,Nb-rich intermediate-temperature precipitate and V-rich low-temperature precipitate with FCC structure.As Nb mass fraction increases from 0.050%to 0.100%,precipitation temperature and quantity of Nb-rich phase are increased from 1210℃to 1270℃and from 6.877×10^-4 to 1.265×10^-3,respectively.Oppositely,the precipitation temperature of Ti-rich phase and V-rich phase is decreased from 1451℃to 1434℃and from 1080℃to 1020℃,respectively.And their precipitation quantity is decreased from 3.663×10^-4 to 2.331×10^-4 and from 5.562×10^-3 to 5.281×10^-3,respectively.The precipitation characteristics of MX under non-equilibrium conditions ob-tained from the experimental study are basically consistent with the thermodynamic calculation results.The submicron particles precipitated in the high-temperature austenite region can pin the grain boundaries and induce the formation of intragranular ferrite,which enhances the fine-grain strengthening effect.The nanoparticles precipitated in the intermediate-temperature two-phase region and low-temperature ferrite region are distributed in the matrix,dislocations and grain boundaries,which can effectively hinder the move-ment of dislocations and improve the precipitation strengthening effect.The combined action of the two aspects mentioned above improves the strength and toughness of structural steel.

The effects of boronizing treatment at different temperatures on the surface microstructure, composition, hardness distribution and residual stress of Ti-55531 lamellar alloy were systematically studied.The results show that the boronized layer of Ti-55531 alloy is composed of three parts: the outer surface layer of bright white product, the transition layer of whisker-like microstructure and the original lamellar matrix.The content of the element B in the boronized layer decreases gradually from the surface to the inside.After boronizing, there is a gradient layer of Ti-B compounds in the surface layer of the alloy, which significantly increases the microhardness of the alloy, and the hardness decreases gradually from the surface layer to the core.Furthermore, the surface of the alloy after boronizing presents a state of residual compressive stress, and its value increases with boronizing temperature increasing.These results of the study can lay a foundation for further study on the effect of boronizing treatment on the wear resistance and fatigue properties of Ti-55531 alloy.

The phase transformation of as-cast Ti₄₉Ni₅₁ alloy samples was tested by differential scanning ca-lorimeter(DSC),and their mechanical properties were tested by cyclic loading and unloading on universal testing machine under the conditions of two ambient temperatures(303Kand 323K)and three strains(6%,7%and 7.5%).The results show that there is no martensite transformation platform or reverse martensite transformation platform during the loading and unloading of the samples at the ambient tempe-ratures of 303Kand 323Kand the strains of 6%,7%and 7.5%.The dissipated energy(W_d) is related to the ambient temperature.When the ambient temperature(303K)is in the stage of martensite transformation,the sample has a relatively large value of dissipated energy W_d during the cyclic loading and unloading with the strains of 6%,7%and 7.5%.However,when the ambient temperature(323K) is in the unstable stage of austenite transformation,the samples with the strains of 6% and 7%have relatively small W_d values during the loading and unloading.In addition,at the ambient temperatures of 303Kand 323K,the change of the recoverable strain energy density W_r value is small with the smaller strain(6%),and tends to be stable with the increase of the cycle number,while the W_r value is less stable or does not show a stable value with the larger strain(7.5%).

The low plasticity and cold brittleness of pure beryllium rolled at room temperature limit the ultra-thin thickness and large-size area of its sheet.Using metallographic microscope, uniaxial tension and rolling tests, the effects of deformation temperature on fracture elongation, maximum pass processing rate and microstructure of pure beryllium sheets were investigated.The results show that with the increase of deformation temperature, the plasticity increases at first and then decreases with a fluctuating trend, and two optimal plastic zones appear at 325~350 ℃ and 600~700 ℃.When the pure beryllium sheet is rolled and deformed in the second optimal plastic zone, the grains are elongated along the rolling direction and undergo a certain degree of dynamic recrystallization, so that the grains are refined and the microstructure is improved to a certain extent.And the higher the rolling temperature, the greater the degree of microstructure improvement.The recrystallization degree of pure beryllium sheets during annealing in the second optimal plastic zone gradually tends to be complete with the increase of temperature.In order to significantly improve the microstructure of pure beryllium sheets and make the recrystallization degree tend to be complete, the hot rolling temperature and annealing temperature should be selected in the range of 600~700 ℃.