Jian Tu

Characterization of basal-prismatic interface of twin in deformed titanium by high-resolution transmission electron microscopy

Disconnections in the basal-prismatic (BP) interfaces of twin have been investigated by many computer simulations. In this paper, we report experimentally that the disconnection in the BP interface of twin in deformed titanium can be observed by high-resolution TEM (HRTEM). This disconnection can be characterized as using a coherent dichromatic complex. Correspondingly, the migration process of the basal-prismatic plane resulting from glide is described.

Microstructure and dry sliding wear behavior of laser clad AlCrNiSiTi multi-principal element alloy coatings

The approximately equimolar ratio AlCrNiSiTi multi-principal element alloy (MPEA) coatings were fabricated by laser cladding on Ti–6Al–4V (Ti64) alloy. Scanning electron microscopy (SEM), equipped with an energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD) were used to characterize the microstructure and composition. Investigations show that the coatings consist of (Ti, Cr)5Si3 and NiAl phases, formed by in situ reaction. The phase composition is initially explicated according to obtainable binary and ternary phase diagrams, and the formation Gibbs energy of Ti5Si3, V5Si3 and Cr5Si3. Dry sliding reciprocating friction and wear tests of the AlCrNiSiTi coating and Ti64 alloy substrate without coating were evaluated. A surface mapping profiler was used to evaluate the wear volume. The worn surface was characterized by SEM–EDS. The hardness and wear resistance of the AlCrNiSiTi coating are well compared with that of the basal material (Ti64). The main wear mechanism of the AlCrNiSiTi coating is slightly adhesive transfer from GCr15 counterpart, and a mixed layer composed of transferred materials and oxide is formed.

Microstructure and Liquid Phase Separation of CuCr Alloys Treated by High Current Pulsed Electron Beam

Microstructures of CuCr25 and CuCr50 alloys treated by high current pulsed electron beam (HCPEB) were investigated in this work. The microstructure and solidification behavior of the Cr-rich phases were characterized by scanning electron microscopy (SEM). Results show that a remelting layer of 3~5 μm is formed on the surface of Cu-Cr alloys. The microstructure of the remelting layer reveals that both the fine dispersion of Cr-rich spheroids and the craters appear after HCPEB treatment. This means that metastable liquid phase separation occurs during rapid solidification under HCPEB treatment. In addition, the appearance of relatively large craters in the subsurface of Cr-rich particles with the distance about 5-10 μm provides direct evidences supporting results reported by other researchers in terms of numerical simulation temperature field of HCPEB treatments.

Microstructural Characterization of Pure Titanium Treated by Laser Surface Treatment Under Different Processing Parameters

Advanced characterization techniques are utilized to investigate the effect of laser surface treatment on microstructural evolution of pure titanium (Ti). The results show that there are three distinctly different types of microstructure from surface to substrate in Ti samples, including phase transformation and solidification microstructure in zone I (melting zone); insufficient recrystallization grains with residual α martensitic plates in zone II (heat-affected zone, HAZ); fully recrystallization microstructure in zone III (base metal, BM). The hardness evolution profiles under different laser treatment parameters are similar. The highest hardness in MZ is ascribed to α plate, while the lowest hardness value in HAZ is due to the insufficiently recrystallized grains. The metallurgical process on the laser-modified Ti samples is systematically discussed in this work.