In-situ neutron diffraction study of lattice deformation behaviour of commercially pure titanium at cryogenic temperature.

Titanium has a significant potential for the cryogenic industrial fields such as aerospace and liquefied gas storage and transportation due to its excellent low temperature properties. To develop and advance the technologies in cryogenic industries, it is required to fully understand the underlying deformation mechanisms of Ti under the extreme cryogenic environment. Here, we report a study of the lattice behaviour in grain families of Grade 2 CP-Ti during in-situ neutron diffraction test in tension at temperatures of 15-298 K. Combined with the neutron diffraction intensity analysis, EBSD measurements revealed that the twinning activity was more active at lower temperature, and the behaviour was complicated with decreasing temperature. The deviation of linearity in the lattice strains was caused by the load-redistribution between plastically soft and hard grain families, resulting in the three-stage hardening behaviour. The lattice strain behaviour further deviated from linearity with decreasing temperature, leading to the transition of plastically soft-to-hard or hard-to-soft characteristic of particular grain families at cryogenic temperature. The improvement of ductility can be attributed to the increased twinning activity and a significant change of lattice deformation behaviour at cryogenic temperature.

Numerical Simulation of the Effects of Scanning Strategies on the Aluminum Evaporation of Titanium Alloy in the Electron Beam Cold Hearth Melting Process.

In the production of titanium alloy, the electron beam cold hearth melting (EBCHM) process is commonly used due to its effectiveness and the high quality of the end product. However, its main drawback is the significant loss of elements such as aluminum (Al) due to evaporation under the vacuum environment. Numerical coupled thermal-flow models were here developed to investigate the effects of scanning strategies on Al loss in a titanium alloy during EBCHM. The validation model was successful in comparison with previously published experimental data. The Al mass fraction results at the outlet of the water-cooled hearth were strongly influenced by changes in the applied scanning strategies. The results indicated that the Al mass fraction loss could be reduced by using the full-hearth scanning strategies.

Fabrication and characterization of novel nano- and micro-HA/PCL composite scaffolds using a modified rapid prototyping process.

Novel three-dimensional scaffolds consisting of nano- and microsized hydroxyapatite (HA)/poly(epsilon-caprolactone) (PCL) composite were fabricated using a modified rapid-prototyping (RP) technique for bone tissue engineering applications. The size of the nano-HA ranged from 20 to 90 nm, whereas that of the micro-HA ranged from 20 to 80 microm. The scaffold macropores were well interconnected, with a porosity of 72-73% and a pore size of 500 microm. The compressive modulus of the nano-HA/PCL and micro-HA/PCL scaffolds was 3.187 +/- 0.06 and 1.345 +/- 0.05 MPa, respectively. The higher modulus of the nano-HA/PCL composite (n-HPC) was to be likely caused by a dispersion strengthening effect. The attachment and proliferation of MG-63 cells on n-HPC were better than that on the micro-HA/PCL composite (m-HPC) scaffold. The n-HPC was more hydrophilic than the m-HPC because of the greater surface area of HA exposed to the scaffold surface. This may give rise to better cell attachment and proliferation. Bioactive n-HA/PCL composite scaffold prepared using a modified RP technique has a potential application in bone tissue engineering.

Hierarchically mesoporous-macroporous bioactive glasses scaffolds for bone tissue regeneration.

Hierarchically 2D/3D mesoporous-macroporous bioactive glasses (MMBG) with good molding capabilities and compressive modulus were synthesized by sol-gel method and evaporation-induced self-assembly process in the presence of both nonionic triblock copolymers, EO(70)PO(20)EO(70) (P123) or EO(100)PO(65)EO(100) (F127), templates and methyl cellulose template. P123 or F127 acts as both a template, inducing the formation of mesopore, and an effective dispersant of MC, which produces macropores. In vitro bioactivity studies were carried out in simulated body fluid and showed superior bone-forming bioactivities of hierarchical MMBG. Human osteoblastlike cells, MG63, were seeded on MMBG and were determined using MTT [3-(4,5-dimethylthiazol-2-yl)-2,5,-diphenyl-tetrazolium bromide] assay to confirm biocompatibilities of MMBG.