Regulation of Ti(C,N)deposition on hot surface of refractory in blast furnace hearth

Ti(C,N)concentration was found to be lower on the hearth sidewall of a blast furnace and increased gradually toward the bottom of the blast furnace.The Ti(C,N)protective layer in a blast furnace is thin.Therefore,the formation of a Ti(C,N)protective layer was promoted by studying the heterogeneous nucleation principle of titanium compounds on different substances and regulation measures for the deposition process of titanium compounds on refractories or impurities.The lattice disregistry between the titanium compounds and the main components in the refractory or the main impurities in the protective layer was calculated using a two-dimensional disregistry equation to study the heterogeneous nucleation principle of titanium compounds.The results revealed that in refractory materials,the heterogeneous nucleation of carbonitride is weak when C,SiO_(2),and Al_(2)O_(3) are used as heterogeneous nucleation substrates,and the heterogeneous nucleation of carbonitride is strong when TiO_(2) and SiC are used as heterogeneous nucleation substrates.As nucleation phases,TiC,TiN,Ti(C_(0.3),N_(0.7)),and Ti(C_(0.5),N_(0.5))have similar heterogeneous nucleation ability in single component refractory,and the type of carbonitride has little effect on the lattice disregistry.The impurities in the protective layer as the substrate phases are not conducive to the heterogeneous nucleation of carbonitride.When CaS was used as the substrate phase,the heterogeneous nucleation ability of carbonitride was the worst.Both carbon and alumina were not conducive to the heterogeneous nucleation of carbonitride,but carbon was more unfavourable than alumina.

Interface optimization of graphene paper-Cu composite prepared by electrodeposition

A room-temperature electrodeposition method with an organic electrolyte was developed to fabricate a HNO3-pretreated graphene paper Cu(GP'-Cu)composite.To improve the interfacial bonding of GP'-Cu composite,magnetron sputtering technology was used to create a"sandwich"structural gradient GP'-Cu composite.The selection of the intermediate transition layer metal was based on two-dimensional disregistry.Scanning electron microscopy,X-ray photoelectron spectroscopy,and other analytical methods confirmed that the addition of an intermediate transition metal(Cr,Ni)layer reduced the gap distance and enhanced the interfacial bonding of the GP'and Cu deposited layers.The GP'-Ni-Cu composite exhibited the largest increase in tensile strength and conductivity.In addition,it had the highest thermal diffusivity and elongation at break among the GP'-Cu,GP'-Cr-Cu and GP'-Ni-Cu composites.

Purifying Fe-based amorphous alloys to enhance glass-forming ability by designing a novel refining slag

Designing low melting point and low basicity refining slag suitable for Fe-based amorphous alloys and understanding the inclusions’formation,removal,influencing mechanisms are quite vital in the fields of metallurgy and materials.In this study,a novel 13%SiO_(2)-32%CaO-30%Al_(2)O_(3)-25%B_(2)O_(3)(wt.%)refining slag was designed after careful calculations of the liquid phase region,slag-metal equilibrium,surface tension,viscosity,deoxidation capability and sulfur distribution ratio.After refining with our designed slag,the content of impurities and the number density of inclusions in a representative Fe_(83)Si_(2)B_(15)(at.%)amor-phous alloy were significantly reduced.Moreover,the glass-forming ability(GFA)of the alloy was also enhanced,enabling the preparation of amorphous ribbons with a lower cooling rate.Based on the impu-rities in Fe-based amorphous alloys as well as the calculated oxide and sulfide free energy diagrams,CaO,SiO_(2),Al_(2)O_(3) oxides and CaS,TiS,MnS sulfides will form in the master alloy.The high melting point in-clusions in the melt are generally removed via a floatation-separation-absorption process and the Mn,Ti,S impurities are removed via slag-metal interface reactions during refining.As for the detrimental effect of inclusions on glass formation,the small lattice disregistry between Ti,Mn-containing inclusions and primaryα-Fe gains reveal that these inclusions are effective in promoting the heterogeneous nucleation,and therefore greatly deteriorate the GFA.These findings are important and provide an ideal solution to purifying the Fe-based amorphous alloys by refining and enhancing the GFA for industrial production.

Effects of Mg Addition on Inclusions Formation and Resultant Solidification Structure Changes of Ti-stabilized Ultra-pure Ferritic Stainless Steel

The effects of Mg addition on the formation of nonmetallic inclusions and solidification structure of Ti-sta- bilized ultra-pure ferritie stainless steels were investigated by experimentally casting ingots with different composi tions. Thermodynamic analyses on the formation of complex inclusions after adding Mg into steels were carried out combined with the scanning electron microscopy energy dispersive spectrometry （SEM EDS） analysis. And the EDS analysis showed that in steel samples with Mg addition, a new spinel crystal phase combined with AI2O3- TiOx formed. It was also found that after Mg addition, the proportions of equiaxed grain zone of 409L, 4003, 439 and 443NT steels increased from 10.2%, 21.8%, 13.4% and 18.6% to 84.3%, 92.3%, 91.1% and 100.0%, respec tively. Since the planar disregistry between spinel and TiN is 5. 1%0, spinel could promote the precipitation of TiN and increase the number density of TiN inclusions in steel melts. The mechanism of solidification structure refinement after adding Mg into steels supposed that the complex inclusions of spinel and TiN in high number density enhanced columnar-to-equiaxed transition, since the planer disregistry between δ phase and spinel is 1.4 %.

Influence of cerium treatment on inclusion modification and as-cast microstructure of high-strength low-alloy steel

The influence of cerium treatment on the inclusion evolution and as-cast microstructure of high-strength low-alloy steel was investigated.Properties including the inclusions characteristics,element distribution,and the in situ solidification were analyzed by scanning electron microscopy,energy-dispersive spectroscopy,and high-temperature confocal laser scanning microscopy,respectively.The results indicated that,after the addition of Ce,the Al_(2)O_(3) inclusions evolved to form Ce_(2)O_(2)S and CeAlO_(3) inclusions,which exhibited a decrease in size alongside corresponding increase in their number density.The equiaxed grain ratio exhibited by the as-cast microstructure increased significantly upon the addition of Ce,while a reduction in the segregation and a corresponding increase in the homogeneity of the carbon distribution within the as-cast microstructure were also achieved.The results of the in situ observation of the solidification suggested that the addition of Ce significantly reduced the solidification temperature range,thus reducing the carbon segregation.The nucleation effect imparted by Al_(2)O_(3),Ce_(2)O_(2)S,and CeAlO_(3) on theδ-Fe formation was discussed in the context of the disregistry theory,which revealed that the formation of a large number of fine Ce_(2)O_(2)S inclusions promotedδ-Fe formation via heterogeneous nucleation.

Morphology and orientation evolution of Cu_(6)Sn_(5)grains on(001)Cu and(011)Cu single crystal substrates under temperature gradient

The morphology and orientation evolution of Cu_(6)Sn_(5)grains formed on(001)Cu and(011)Cu single crystal substrates under temperature gradient(TG)were investigated.The initial orientated prism-type Cu_(6)Sn_(5)grains transformed to non-orientated scallop-type after isothermal reflow.However,the Cu_(6)Sn_(5)grains with strong texture were revealed on cold end single crystal Cu substrates by imposing TG.The Cu_(6)Sn_(5)grains on(001)Cu grew along their c-axis parallel to the substrate and finally merged into one grain to form a fully IMC joint,while those on(011)Cu presented a strong texture and merged into a few dominant Cu_(6)Sn_(5)grains showing about 30°angle with the substrate.The merging between neighboring Cu_(6)Sn_(5)grain pair was attributed to the rapid grain growth and grain boundary migration.Accordingly,a model was put forward to describe the merging process.The different morphology and orientation evolutions of the Cu_(6)Sn_(5)grains on single crystal and polycrystal Cu substrates were revealed based on crystallographic relationship and Cu flux.The method for controlling the morphology and orientation of Cu_(6)Sn_(5)grains is really benefitial to solve the reliability problems caused by anisotropy in 3 D packaging.

Relationship between crystallographic structure of complex inclusions MgAl_(2)O_(4)/Ti2O_(3)/MnS and improved toughness of heat-affected zone in shipbuilding steel

In accordance with the minimum degree of disregistry mechanism in oxide metallurgy, the intragranular acicular ferrite (IAF) generated by microalloying elements in austenite was studied. Herein, the effect of Mg treatment on the microstructure and toughness of the heat-affected zone (HAZ) in shipbuilding steel was investigated. Mg treatment produced inclusions that influenced the formation of acicular ferrite in the microstructure. This refined the HAZ microstructure and improved its toughness. Electron backscatter diffraction was used to determine the oxides of titanium and the MgO Al_(2)O_(3) or MgAl_(2)O_(4) complex inclusions that induced the formation of IAF. MnS precipitated on MgAl_(2)O_(4) on a specific habit plane and in a specific direction. MnS had a specific orientation relationship with MgAl_(2)O_(4), i.e., f100gMgAl_(2)O_(4) //{100}MnS. The 35-mm-thick plate obtained in the industrial test after welding at a welding heat input of 120 kJ/cm had an average impact absorbed energy of 282.7 J at - 40 ℃ and 2 mm from the weld joint in the HAZ. The twodimensional disregistry index between inclusions can be used as the basis for controlling their distribution and adsorption force. Microalloy addition in the order of Al-Mg-Ti is key to obtaining abundant dispersion and fine nucleation in austenite.

Solidification structure refinement of ferritic stainless steel based on heterogeneous nucleation technology

The ridging defect on the surface of stainless steel products is related to the solidification structure of ferritic stainless steel.Refining the solidification structure and increasing the proport io n of equiaxed grains are necessary to lesse n the ridging defect.Therefore,a new idea of using a heterogeneous nucieating agent which was composed of the composite core containing Ti was proposed,that is,a large amount of dispersed fine particles were initially formed on the solidification front,and a great amount ofδiron was then nucleated using these fine particles as the heterogeneous cores.Through analyzing the crystallographic relationship between different crystals and inducing the calculation formulas of disregistry,the disregistry between the different oxides and TiNδiron was explored and the type of nucleation core was determined.The key parameters of forming the composite core containing Ti were obtained through a thermodynamic calculatio n.The experimental results further con firm the correctness of the theoretical analysis.

Precipitation and Growth of Inclusions in Solidification Process of Steel

The formation and growth behavior of inclusions in the liquid steel were studied based on 45 steel by virtue of high temperature confocal laser scanning microscope.The structures of all kinds of complex inclusions formed in the process of cooling and solidification of liquid steel were analyzed,and disregistries between various inclusions were calculated.The results showed that inclusions with high melting point precipitated firstly,and inclusions with low disregistries precipitated later.The latter precipitated and grew up on the surface of the former,and finally clear layered complex inclusions formed.The low disregistry mechanism could not fully explain the forming reasons of all complex inclusions,but no matter which kind of mechanism leading to the formation of complex inclusions,its basic principle is that the first precipitated phase provides a low nuclear power interface for the latter,which can reduce the nucleation interface and strain energy barrier of the latter.

Grain refining efficiency and mechanism of pure nickel

According to the selection principle of grain refiners and calculation of planar disregistries, CeO2 and TiB2 particles were selected as the grain refiners of pure nickel. The change of grain size and refining effects of different refiners under the same melting conditions were investigated. The results show that the grain size of pure nickel gradually reduces with increasing the amount of grain refiners. And with increasing the amount of CeO2 up to 0.7 wt%, the grain size of pure nickel decreases from 323.0 to 53.5 lm. In addition, when the amount of TiB2is0.7 wt%, the grain size is reduced to 41.3 lm.