Texture Evolution during Recrystallization and Grain Growth in Non-Oriented Electrical Steel Produced by Compact Strip Production Process

Evolution of texture and α*-fiber texture formation mechanism of Fe-0.65%Si non-oriented electrical steel produced by Compact Strip Production (CSP) process during all the thermo-mechanical processing steps were investigated using electron backscatter diffraction (EBSD) and X-ray diffraction (XRD) techniques. Columnar crystal structure of cast slab is fine and well-developed. Textures of the hot-rolled band are quite different in the thickness direction. During annealing of cold-rolled sheet, γ-fiber texture grains would nucleate and grow preferentially, and α*-fiber texture grains mainly nucleate and grow in the shear zone of α-fiber texture of cold-rolled sheet. During the recrystallization process, γ-fiber texture gradually concentrated to {111}<112>, and γ and α*-fiber texture increased significantly. {111}<112> texture priority nucleation at the initial stage of recrystallization. Due to the advantages of nucleation position and quantity, the content of α*-fiber texture is greater than {111}<112> texture in the mid-recrystallization. During grain growth process, {111}<112> oriented grains would grow selectively by virtue of higher mobility, sizes and quantity advantages than that of {411}<148 > and {100}<120>, resulting in the gradual increase of γ-fiber texture and the decline of α *-fiber texture.

Numerical Simulation of Solidification Structure of Al Alloy During Centrifugal Casting

The centrifugal casting process of 6082 Al alloy was simulated by ProCAST software. The effects of rotation speed and heat transfer coefficient on the filling and solidification behaviour were analysed. The porosity of the cast pipe increases with the increase of the rotation speed and decreases with the increase of heat transfer coefficient. The CAFE model was used to simulate the grain structure of centrifugal cast Al alloy under different process conditions. When the rotation speed and heat transfer coefficient increase, the length of columnar crystal region will increase and the grain will be refined.

Microstructure of the coating obtained by magnetron sputtering of a Ni-Cr-B4C composite target

This paper presents data on obtaining a composite coating by radio frequency (RF) magnetron sputtering of a Ni-Cr-B4C composite target in an inert gas (argon) environment. To make the target, Ni-Cr-B4C composite powder was applied to the copper base of the target by detonation gas-thermal spraying. The obtained targets served as a source of coating material during high-frequency magnetron sputtering. This method of coating production ensures the reproducibility of their properties, as well as the uniformity of coating thickness and good adhesion to various target backings. The data of the study of the structure and morphology of the composite coating are presented. The resulting composite coating Ni-B/Cr7C3 with a thickness of 2 microns has a dense homogeneous structure with expressed textured polycrystallinity. The surface of the resulting coating is represented by nanoscale and homogeneous grains. There is no columnar crystal growth in the coating, which has a positive effect, as the columnar structure reduces the mechanical characteristics of the coatings due to faster oxygen diffusion along the grain boundaries. It is established that the combined use of the Ni-B and Cr7C3 binary phases in composite coatings leads to an increase in operational properties.

HIGH-TEMPERATURE OXIDATION BEHAVIOR OF AN N5 NANOCRYSTALLINE COATING DEPOSITED BY ESD ON A NI-BASED SINGLE-CRYSTAL SUPERALLOY

An N5 nanocrystalline coating was prepared on a Ni-based single-crystal superalloy by electrospark deposition. The morphologies, chemical composition, and phase constitution of the coating were analyzed by scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS) and X-ray diffraction (XRD), respectively. The high-temperature oxidation resistance of the substrate and coating at 1100℃ was tested in a static isothermal oxidation experiment. The results show that the electrospark deposition coating with columnar crystal structure is composed of nanocrystalline; there is no elemental interdiffusion between the substrate and the coating, which effectively avoids decreasing the mechanical properties of the substrate alloy due to the interdiffusion. Migration and aggregation of a reactive element, Ta, in the nanocrystalline coating substantially improves oxide film adhesion

Effect of Laser Welding Speed on Grain Morphology and Tensile Property of TA15 Titanium Alloy Bottom-Locking Joint

The laser welding of TA15 titanium alloy with the bottom-locking joints is carried out by TruDisk-12003 disc laser. In this paper, the microstructure and tensile properties of welded joints with different welding speeds are studied. The microstructure is observed by optical microscope. The tensile fracture morphology and chemical composition are analyzed by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) respectively. The experimental results show that the width of weld zone (WZ) is decreased significantly with the increasing of welding speed. The β columnar crystal shows respective morphology and growth direction in WZ under different welding speeds, meanwhile, the number of acicular martensite which is precipitated in columnar crystal also presents different. Besides, the aggregate growth zone of columnar crystal at the bottom of weld zone gets smaller with the increase of welding speed. The maximum tensile strength for the TA15 titanium alloy bottom-locking joint, which is fractured at weld joint, reaches 89% of the BM. Besides, the EDS results illustrate that the burning loss of stabilization element is inevitable.

Effect of Thermal Behavior on the Grain Morphology and Dimension of 80mm-Thick Ti6Al4V Plates Joined by Laser Melting Deposition

Individually fabrication forged parts and then joining them together through Laser Melting Deposition (LMD) is a viable way for manufacturing large components. For investigating the effect of the grain morphology of LMD joint, two 80mm-thick Ti6Al4V plates are successfully manufactured using three different scanning speeds (10, 15, and 20 mm/s). It is essential for understanding the thermal behaviour of melt pool during LMD to improve process quality. This study focuses on the energy density of heat source and the direction of heat flux, analyzing the effect of thermal behavior on the grain morphology and dimension of deposition area, equiaxed crystal zone (EQZ) and the substrate. The macrostructure is evaluated in the different thermal condition and scanning speeds. An extremely fine equiaxed crystal was observed near the joint boundary with a high temperature gradient and cooling rate. The curve epitaxial growth of fine columnar crystal rather than along straight lines is induced by the direction of heat conduction near the joint boundary. However, the orientation angle of epitaxial growth of the coarse columnar crystal is the same as previous deposition layer at the center of deposition area. Given the effect of high heat accumulation and low temperature gradient during LMD, the dimension of columnar crystal is coarsen significantly at the center of deposition area.

Flow Cessation Mechanism of β-Phase Solidification of High-Nb Tial Alloy

The spiral fluidity sample was poured by the liquid of Ti-45Al-8Nb-0.2W-0.25Cr alloy. The flow cessation mechanism of TiAl based alloys was investigated, and its model was built through the observation on the macrostructure of TiAl based alloys formed in the channel. The results showed that the morphology and size of the columnar crystal and equiaxial crystal changed a lot with the increase of flow length. The flow cessation mechanism of the alloy is the abundant growth of columnar crystal in the root, which causes to form the structure and finally give rise to the “necking” leading to flow cessation.