Investigation of early stage deformation mechanisms in a metastable β titanium alloy showing combined twinning-induced plasticity and transformation-induced plasticity effects

International audienceAs expected from the alloy design procedure, combined Twinning Induced Plasticity (TWIP) and Transformation Induced Plasticity (TRIP) effects are activated in a metastable β Ti-12(wt.%)Mo alloy. In-situ Synchrotron X-ray diffraction (XRD), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) observations were carried out to investigate the deformation mechanisms and microstructure evolution sequence. In the early deformation stage, primary strain/stress induced phase transformations (β->ω and β->α'') and primary mechanical twinning ({332} and {112}) are simultaneously activated. Secondary martensitic phase transformation and secondary mechanical twinning are then triggered in the twinned β zones. The {332} twinning and the subsequence secondary mechanisms dominate the early stage deformation process. The evolution of the deformation microstructure results in a high strain hardening rate (~2GPa) bringing about high tensile strength (~1GPa) and large uniform elongation (> 0.38)

On the suitability of cerium oxide glass for terminal radiation sterilization

The affect of ammonium sulphate treatment on cerium oxide (CeO) glass vials have been assessed following exposure to ionizing radiation at 25 kGy. The bulk chemical composition of irradiated cerium oxide glass remains unchanged despite a temporary browning effect. Stability against alkali leachables of the internal silica matrix is enhanced with ammonium sulphate treatment. With exception to Alumina and Na2O, radiation sterilization has a limited effect on altering the surface chemistry of ammonium sulphate treated cerium oxide glass. (C) 2004 Elsevier Ltd. All rights reserved

Improved mechanical properties of β metastable Ti alloys processed by laser powder bed fusion

This study proposes a thorough investigation of the mechanical properties of two β metastable titanium alloys(Ti–12Mo and Ti-8.5Cr-1.5Sn (wt %)) processed by laser powder bed fusion. Particular emphasis is put on theinfluence of chemical homogenization and defects formation as a function of the processing parameters. It isdemonstrated that the Transformation/Twinning – induced plasticity (TRIP/TWIP) mechanisms already revealedas beneficial in the case of wrought alloys, still bring a larger work hardening level and a larger ductility in thecase of laser powder bed fusion (L-PBF) processing. Improved mechanical properties in terms of yield and ultimatetensile strengths with similar uniform deformation compared to the wrought counterparts are thus achievedafter L-PBF and a very short annealing

A new titanium alloy with a combination of high strength, high strain hardening and improved ductility

International audienceA ternary beta-metastable titanium Ti-9Mo-6W (wt.%) was designed. A very high work hardening rate close to 2100 MPa and a uniform deformation larger than 35% were recorded, thanks to combined transformation-induced plasticity and twinning-induced plasticity effects. In this paper, detailed microstructural analysis was performed to understand the deformation process. Various mechanisms, {332} mechanical twinning, stress-induced omega phase and stress-induced alpha '' martensite were identified after mechanical testing, resulting in a complex network of deformed microstructures with very special synergetic features

New titanium alloys with a combination of high strength, strain hardening and high ductility, induced by TRIP and TWIP effects

International audienc

The role of stress induced martensite in ductile metastable Beta Ti-alloys showing combined TRIP/TWIP effects

International audienceA new family of metastable beta type titanium alloys has recently been designed for ductility improvement with large strain-hardening effect. Superior plastic properties were obtained due to collective effects of both phase transformation induced plasticity and twinning induced plasticity. A series of stress induced phase transformations, including stress/strain-induced beta to omega transformation and stress-induced martensitic beta to α” transformations, play particular roles at each deformation stage. The SIM transformations were found to be closely related to the strain-hardening behavior of the material. In this work, the relationship between SIM transformations and strain-hardening effect were studied by microstructural investigations