Papers by Author: J.F.C. Lins

Abstract: The alpha-beta Ti-5%Al-2.5Fe (wt-%) alloy was developed as a cost-effective option to replace the traditional Ti-6%Al-4%V alloy in the manufacture of surgical implants because of its larger biocompatibility (V-free alloy). Samples of this alloy were prepared using the blended elemental (BE) technique. The isochronal sintering of the cold pressed compacts was carried out at 700, 1000, and 1400°C in vacuum. In this work, the preliminary results of the behavior of elementary powders during sintering and the corresponding microstructural evolution are shown. The alloy was characterized by means of scanning electron microscopy (SEM) in the backscattered mode, X-ray diffraction (XRD), energy-dispersive spectrometry (EDS), and density measurements. The results indicate that the homogenization of the alloy is diffusion-controlled. Non-equilibrium Ti-Al phases as well as Fe-Al compounds were identified in samples sintered at lower temperatures (700oC). With increasing temperature, homogenization of the alloy takes place and a structure consisting of coarse plate-like alpha and intergranular beta is present.

Abstract: We report the results of the microstructural characterization of a Ti-bearing IF-steel deformed at high strain rates (» 6.104 s-1) in a split Hopkinson bar. The shock-loading tests were performed in hat-shaped specimens to induce the formation of adiabatic shear bands (ASB). The samples were deformed at 223 K and 298 K. High-resolution electron backscatter diffraction (EBSD) reveals the development of an ultrafine-grained structure within the ASB. A closer inspection reveals the presence of deformation twins in grains adjacent to the shear band. These twins bend towards the ASB suggesting that mechanical twinning occurs before the flow associated to shear banding. The results of microtexture have indicated the presence of a sharp <111> g-fiber texture in the ASB for both temperatures.