Properties,Microstructures and Precipitate Morphology of Hot-rolled Interstital-Free(IF)Steel Sheets

In order to simplify production process and to decrease production cost of thicker cold-rolled iF steel sheets for deep drawing applications, a new hot-rolled IF steel sheet is developed through hot-rolling in or region. In this paper, properties, microstructures and precipitate morphology of hot-rolled iF steel sheets are described..

SOLIDIFICATION MICROSTRUCTURE AND FRACTURE MORPHOLOGY OF SiCp/ZA27 COMPOSITE

Solidification microstructure and mechanical property are explored.Furthermore,tensile fracture and microstructure are analyzed by using SEM and JXA 840A electron probe.The results indicate that SiC particles in SiCp/ZA27 composite are mainly distributed on interfaces or between dendrites and surrounded by primary α phase.The dendrite of α phase is fined by SiCp.The tensile strength at room temperature decreases with the increasing of SiCp addition.The tensile strength at elevated temperature increases with the addition of SiCp.The fracture of SiCp/ZA27 composites is the mixture of tough and brittle fracture.The carck is prone to extend along the interface and the region of dispersed shrinkage.

NEAR RAPID DIRECTIONAL SOLIDIFICATION AND ITS SUPERFINE MICROSTRUCTURE

This paper briefly reviews the recent research on the near rapid directional solidification and microstructure superfining. The morphology transitions and the corresponding mechanical properties are presented. The critical velocities relevant to the morphology transitions are comprehensively given. Meanwhile the solidification characteristics near absolute stability limit are studied.It can be clearly seen that the superfine microstructures possess extremely better properties compared with the conventional microstructures.

Microstructure Morphologies of Asphalt Binders using Atomic Force Microscopy

We investigated microstructure morphologies of three asphalts（SK, Karamay, and Esso） used in China using atomic force microscopy（AFM）. The topography and phase contrast images were obtained. Topographic profile and three dimensional images were described. Roughnesses of microstructure were calculated. And the chemical compositions of asphalt were tested to explain the microstructural mechanism of the asphalt. The results show that the topography and phase image in atomic force microscopy are appropriate to evaluate the microstructure of the asphalt binder. There are significant differences in microstructural morphologies including bee-like structure, topographic profile, 3D image, and roughness for three asphalts in this study. There are three different phases in microstructure of asphalt binder. The oil source and chemical composition of asphalt, especially asphaltenes content have a great influence on the microstructure.

Microstructural morphology of the semi-solid high carbon steel T12 before and after rheo-rolling

The semi-solid high carbon steel T12 was rolled in a closed box groove under a certain condition by the rheo-rolling equipment, and the microstructural morphology of the semi-solid T12 before and after deformation was investigated by optical mi- croscope to analyze and summarize the microstructure evolution law of T12 deformed in semi-solid state. The experiment results show that the grain shape before deformation of the semi-solid T12 steel displays globule or ellipse by the electromagnetic stirring, the distribution of solid and liquid phases is homogeneous. But the microstructure of semi-solid product after rheo-rolling exhibits macrosegregation that the distribution of liquid and solid phases changes, the liquid phases divorce from the solid phases. In the transverse section, most of the solid phases get together in the center of the specimen, the liquid phases flow to the surface or the edge of the specimen, and the grains occur plastic deformation while reduction increased. In longitudinal section, the middle micro- structure of the specimen is more homogeneous than that at the head or tail, the head microstructure is similar to the tail and the size of the grains is not homogeneous.

Morphological and Microstructural Evolution and Related Impurity Incorporation in Non-Polar a-Plane GaN Grown on r-Sapphire Substrates

Effects of the growth temperature on morphological and microstructural evolution of a-plane GaN films grown on r-plane sapphires by metal organic chemical vapor deposition are investigated by atomic force microscopy and secondary ion mass spectroscopy （SIMS）. Surface morphology, structural quality and related impurity incorpora- tion are very sensitive to the growth temperature. A significant difference of yellow luminescence is observed and attributed to the incorporation of carbon into GaN films, which is confirmed by SIMS analysis. Our results show that the sample with triangular-pit morphology has sample with pentagon-like pit morphology, which is significantly higher concentrations of oxygen than the other induced by the existence of an N-face in triangular pits.

Mechanical Anisotropy of Selective Laser Melted Ti-6Al-4V Using a Reduced-order Crystal Plasticity Finite Element Model

In this study,a reduced-order crystal plasticity finite element(CPFE)model was developed to study the effects of the microstructural morphology and crystallographic texture on the mechanical anisotropy of selective laser melted(SLMed)Ti-6Al-4V.First,both hierarchical and equiaxed microstructures in columnar prior grains were modeled to examine the influence of the microstructural morphology on mechanical anisotropy.Second,the effects of crystallographic anisotropy and textural variability on mechanical anisotropy were investigated at the granular and representative volume element(RVE)scales,respectively.The results show that hierarchical and equiaxed CPFE models with the same crystallographic texture exhibit the same mechanical anisotropy.At the granular scale,the significance of crystallographic anisotropy varies with different crystal orientations.This indicates that the present SLMed Ti-6Al-4V sample with weak mechanical anisotropy resulted from the synthetic effect of crystallographic anisotropies at the granular scale.Therefore,combinations of various crystallographic textures were applied to the reduced-order CPFE model to design SLMed Ti-6Al-4V with different mechanical anisotropies.Thus,the crystallographic texture is considered the main controlling variable for the mechanical anisotropy of SLMed Ti-6Al-4V in this study.

Effects of heating rate on the alloy element partitioning and mechanical properties in equiaxedα+βTi-6Al-4V alloy

The effects of heating rate on the alloy element partitioning and mechanical properties during the phase transformation ofα→βin Ti-6Al-4 V alloy under solution treatment have been investigated by the experiments and phase field simulations,which reveal the evolutions of microstructure and compositions at the non-equilibrium state and well verify the experimental results.The specific results indicate that the compositions measured through electron probe micro-analysis(EPMA)under a lower heating rate are close to the equilibrium ones corresponding to the solution temperature.Heating up to the target solution temperature,as the heating rate increases,the Al content decreases and V increases in the primaryα(α_(p))grain with a larger size,the volume fraction ofα_(p)increases and the composition gradient betweenα_(p)andβphases gets steeper.The interrelated relationship among the diffusion,compositions,solution temperature and free energy of the system has been discussed in detail.Moreover,increasing the heating rate(~20.0 K/min)may help to improve the mechanical properties of the alloy by mainly adjusting theα_(p)/β;volume fractions,α_(p)particle size and secondaryα(α_(p))size during the process of heating up to the solution temperature.These results may shed some light on the optimization of the knowledge-based heat treatment route.