Effects of Homogenization Heat Treatment on the Fe Micro-Segregation in Ti-1023 Titanium Alloy.

The segregation of the Fe element in Ti-10V-2Fe-3Al titanium alloy (Ti-1023) can lead to the generation of beta flecks, which seriously affects the performance of Ti-1023 products. During the heat treatment (HT) process at a high temperature, the Fe element in Ti-1023 ingots will migrate, making its distribution more uniform and reducing the segregation index. In this paper, the control of Fe micro-segregation in Ti-1023 ingots by homogenization HT was investigated. Firstly, dissection sampling and SEM-EDS analysis methods were used to study the distribution pattern of the Fe element in the equiaxed grains in the core of Ti-1023 ingots. It was found that the Fe content in the grain gradually increased along with the radial direction from the core to the grain boundary. Then, the homogenization HT experiments and numerical simulations of Ti-1023 at different HT temperatures from 1050 °C to 1200 °C were carried out. The results showed that the uniformity of Fe element distribution within grain can be significantly improved by the homogenization HT. With increasing HT temperature, Fe atoms migration ability increases, and the uniformity of Fe element distribution improves. Homogenization HT at 1150 °C and 1200 °C for 12 h can effectively reduce the degree of Fe element segregation.

Large-area epitaxial growth of MoSe2 via an incandescent molybdenum source.

We have developed an incandescent Mo source to fabricate large-area single-crystalline MoSe2 thin films. The as-grown MoSe2 thin films were characterized using transmission electron microscopy, energy dispersive x-ray spectroscopy, atomic force microscopy, Raman spectroscopy, photoluminescence (PL), reflection high energy electron diffraction (RHEED) and angular resolved photoemission spectroscopy (ARPES). A new Raman characteristic peak at 1591 cm-1 was identified. Results from Raman spectroscopy, PL, RHEED and ARPES studies consistently reveal that large-area single crystalline mono-layer of MoSe2 could be achieved by this technique. This technique enjoys several advantages over conventional approaches and could be extended to the growth of other two-dimensional layered materials containing a low-vapor-pressure element.