The influences of non-metallic inclusions on the quality and properties of the steel not only depended on the quantity of inclusions, but also on the type、shape、size、deformation behavior and distribution condition. By means of ANSYS finite element analysis software, the stress field distribution in the inclusions and the matrix around the inclusions are analyzed under the condition of different kinds of types、shapes、distributions with changeable load in heavy rudder arm steel castings, then micromechanics behavior of inclusions is investigated from angle of macro mechanics.

The YBCO powder was prepared by oxalic acid precipitation method and consequent annealing. The correlation between pH values of oxalic acid solution and the precipitation percentage of precursors were analysed based on thermodynamics analysis. The differential scanning calorimetryanalysis (DSC) was used to confirm the synthetic technological parameter. The phases of powder in each process were investigated by XRD. The microstructures of each powder were tested by SEM and TEM. The mean grain size was calculated by the scherrer’s equation. The test results indicated that the YBCO powder with high purity, less impurities, smaller particle, but severe agglomeration, was Y123 when annealing at 900°C. However, adding dispersants could effectively solve the severe agglomeration. The size of YBCO particles was nanosized and coincided with the calculation.

The grain size of W-Cu nanocomposites would greatly affect the density of W-Cu alloy. In this work, W-Cu oxide nanocomposite powders were prepared by sodium tungstate and copper nitrate via hydrothermal method, and W-Cu nanocomposite powders were obtained by subsequently co-reduction process. The characterization of W-Cu nanocomposite powders were carried out by X-ray diffraction (XRD), scanning electron microscope (SEM), energy spectrum analysis (EDS) and transmission electron microscope (TEM). The results indicated that hydrothermal method was a good method for the preparation of W-Cu oxide nanocomposite powders. W-Cu nanocomposite powders, whose grain size was about 70nm and distributed uniformity, were manufactured by co-reduction process.

The influences of non-mentallic inclusions on the quality and properties of the steel are depended not only on the quantity of inclusions, but also on the type、shape、size、deformation behavior and distribution condition. The effects of lanthanide rare earth(RE) on the shape、size and distribution condition of inclusions in large rudder arm steel casting is investigated. It was proved that the shape and distribution of inclusions could be improved in the large rudder arm steel casting, and the plastic and toughness of the steel can be increased obviously by the rare earth modification. By means of ANSYS finite element analysis software, the stress field distribution around matrix was simulated, and the reaction mechanism of inclusions by modification was clarified.

In this paper , by SEM、EDS、XRD and Shimadzu AG-I250KN precision universal testing machine , the metallurgical structure, fracture appearance, the mechanical properties of the ZA303 under high temperature were systematically studied .The results shows that :The microstructure of ZA303 at room temperature are : α phase + (α＋η) eutectoid + ε phase + η phase. After adding modifying elements B、Ti in ZA303：the microstructure of the alloy is from gross dendrites to uniform equiaxed grains , the quantity, morphology and distribution of the (α + η) have greatly change: the quantity of (α + η) is less, from a continuous network to intermittent block, and its end become blunt, or even cylindrical horn and dispersed distribution; on the grain boundary, the size of ε phase become smaller and dispersed distribution, the number of mesh ε phase reduced but intermittent strips increased; adding B、Ti have a good effect of restraining Al element segregation，so the foundry defects decreased obviously. In the range of experimental temperature, the increase of ductility is large while the tensile strength is small: at the same time, the mechanical performances stability is better than that without modification.