Microstructure Analysis and Bulk Texture Study in Wide Magnesium Alloy Sheets Processed by Twin-Roll Casting

The wide magnesium (Mg) alloy sheets produced by twin-roll casting (TRC) are prone to have an inhomogeneous microstructure and basal texture. Texture has a significant effect on the properties of Mg alloy sheets for the processes after TRC, which can be greatly modified by alloy composition. However, systematic studies on the bulk texture of TRCed Mg alloy sheets using neutron diffraction are lacking. In this study, neutron diffraction was used to explore the bulk textures in different positions of the Mg, Mg–Al–Zn, and Mg–Al–Sn–Zn alloy sheets produced by TRC, besides microstructure and micro-texture analysis using field emission scanning electron microscopy and electron backscattering diffraction. The influence of alloy composition on the microstructure and texture evolution of TRCed Mg alloy sheets is explored and discussed. The TRCed pure Mg sheet possesses a relatively strong basal texture, and the texture distribution is inhomogeneous; while TRCed Mg–Al–Sn–Zn alloy sheets feature much weaker textures and a relatively homogenous distribution in different positions. The present study provides guidance for the control of texture via tailoring alloy compositions, which provides candidate Mg alloys suitable for the TRC process.

Study on Laser Surface Hardening Behavior of 42CrMo Press Brake Die

Laser surface hardening is a promising surface technology to enhance the properties of surfaces. This technology was used on the 42CrMo press brake die. Its hardening behavior was investigated by using scanning electron microscopy and electron backscattering diffraction. The results indicated that the martensite in the hardening zone was significantly finer than that in the substrate. There were many low-angle grain boundaries in the martensite of the hardening zone, and the kernel average misorientation and grain orientation spread in the hardening zone grains were obviously greater, which further improved the hardness of the hardening zone, especially near the substrate. The microstructure and the properties of the blade maintained excellent uniformity with treatment by single-pass laser surface hardening with a spot size of 2 mm, scanning speed of 1800 mm/min, and power of 2200 W. The hardness of the hardening zone was 1.6 times higher than that of the base material, and the thickness of the hardening zone reached 1.05 mm.

Alkali-silica reaction (ASR) - Investigation of crystallographic parameters of natural sands by backscattered electron diffraction

abstract: This study involved analyzing several natural sands to ascertain the possible causes for distress due to ASR. The analyses were performed using the following techniques: X-ray diffractometry, accelerated mortar bar tests (AMBT), electron backscattering diffraction and elementary chemistry analyses, by FEG-SEM/EBSD/EDS. These experiments allowed identifying the presence of several mineral composites (such as microcline, anorthite, among others), as well as the microstructural-crystallographic planes of quartz (such as the Dauphiné type). From the results it could be inferred that the multiple techniques used, especially the FEG-SEM / EBSD, proved to be promising in the analysis of the ASR potential of sands for use in Portland cement mortars and concretes.

Microstructure and mechanical properties of brazing joint of silver-based composite filler metal

In this article, environmental friendly BAg25Cu40Zn34Sn (BAg-25) and BAg30Cu37Zn32Sn (BAg-30) flux-core solder metal capable of facilitating automatic production of brazing manufacturing processes were prepared. The butt and lap induction brazing tests were carried out on the substrate with BAg-25 and BAg-30. Wettability, microstructure and mechanical properties of the solders on the base metal were studied by field emission scanning electron microscope (SEM-EDS), electron backscattering diffraction (EBSD), tensile testing machine and microhardness tester. Results indicated that the wetting property of BAg-30 with 30% silver content was better than that of BAg-25 with 25% silver content. At the same time, besides copper and silver-based solid solutions, the brazed joint of BAg-30 solder also contain Cu + Ag eutectic phase. In the brazed joint of BAg-25 solder, the grain size is smaller, which makes the tensile strength and the shear strength of the joints better. Therefore, the BAg-25 flux-core solder metal will further reduce the industrial cost and meet the requirements of mechanical properties.

Effects of Cryogenic Treatment and Tempering on Mechanical Properties and Microstructure of 0.25C-0.80Si-1.6Mn Steel

The effects of mechanical strength and yield ratio on the seismic steel are significant. This paper investigated the mechanical strength and yield ratio of medium carbon seismic steel by deep cryogenic treatment at −60°C and −110°C for 60∼120 s and tempering at 350°C for 30 minutes. The microstructure, misorientation, grain boundary, and size were characterized by electron backscattering diffraction (EBSD), scanning electron microscopy (SEM), and energy dispersive spectrometery (EDS). The result shows that the tensile strength and reduction of the cross-sectional area of steel were increased by 170 MPa and 9% and yield ratio and elongation were decreased by 0.13 and 9% due to the existence of the large-angle grain boundary. The present study confirms that the mechanical properties of medium seismic steel can be improved effectively by the deep cryogenic treatment and tempering.

XPS Studies of the Initial Oxidation of Polycrystalline Rh Surface

Increased interest in the oxidation process of polycrystalline rhodium, observed in recent years, is the result of its application in exhaust catalytic converters. However, most studies have involved sample surfaces with low Miller indices. In our research, we investigated polycrystalline rhodium foil containing crystallographically different, highly stepped, µm-sized crystallites. These crystallites were exposed to identical oxidizing conditions. To determine crystallographic orientation, the electron backscattering diffraction (EBSD) method was used. To investigate the initial stages of oxidation on the individual crystallites of Rh, X-ray photoelectron spectroscopy (XPS) studies were performed. The results obtained for the individual crystallites were compared and analyzed using chemical state quantification of XPS data and multivariate statistical analysis (MVA).

Microstructure-twinning relations in beta-Ti alloys

We have investigated twinning-microstructure relations in β-Ti alloys by statistical analysis of the evolving twin structure upon deformation by in-situ SEM testing and electron backscattering diffraction (EBSD). In particular, we have analyzed the effects of crystallographic orientation, grain size and chemical gradient structure on the nucleation and propagation behavior of {332}<113> twins in a β-Ti-15 Mo (wt.%) alloy and a multilayered β-Ti-10Mo-xFe (x: 1-3 wt.%). Microstructural parameters such as number of twins per grain and number of twins per grain boundary area were statistically analyzed.