This work proposes studying the softening kinetics of aluminum alloy 7075-T6. Firstly, AA 7075 strips were overaged (300°C and 5 hours). Then, the overaged strips were cold-rolled at room temperature (45% in thickness reduction) and, after that, annealed at different temperatures (200°C and 250°C) and time intervals (30 minutes - 4 hours). By using polarized light microscopy, EBSD and Vickers hardness measurements, the softening mechanisms were determined and proper mathematical models (Kuhlmann, Johnson-Mehl-Avrami-Kolmogorov and Austin-Rickett) were used to analyse the experimental data. The results show that although almost all observed softening can be attributed to recovery, the phenomena is well described by using mathematical models for phase transformations (JMAK and Austin Riccket). In order to promote recrystallization of overaged AA 7075, an additional thickness reduction (75%) were used. These samples were annealed isocronically during 1 hour (100 - 400°C) and it was found that recrystallization only took place at 400°C.
Desde 2004, o CCDM realiza ensaios mecânicos em implantes ortopédicos. Os componentes mais utilizados - e conseqüentemente ensaiados - são parafusos, comumente fabricados com aço inoxidável ASTM F138, ou liga de titânio ASTM F136. O objetivo desse trabalho é avaliar os resultados referentes aos ensaios de torção em parafusos metálicos, dando um panorama das propriedades médias dos produtos ensaiados. Tais resultados provieram de material fornecido por 15 fabricantes diferentes, num total de 451 ensaios, que cobriram quase todo o espectro de parafusos utilizados em implantes: ortodontia, parafusos pediculares, parafusos para ossos corticais e esponjosos, parafusos de bloqueio e de ancoragem. A dispersão dos resultados de ângulo de ruptura é elevada. A maioria dos resultados, no entanto, apresenta valores acima do mínimo exigido pela norma ASTM F543.
Since 2004, the CCDM lab performs tests on orthopedic implants. The most used (and tested) implants are screws. These are commonly made either of austenitic stainless steel ASTM F138 or of Ti-6Al-4V alloy ASTM F136. The aim of this study was to evaluate the obtained torsion test results and to present an overview of the average product properties. The results stand for 15 different producers, and 451 samples, covering almost all the screw types utilized in implants: orthodontic, anchor and tibial nail applications, and designs for pedicular, cortical and cancellous bones. The dispersion in angle of rupture was high. Nevertheless the majority of the results lied above the minimum required by the ASTM F543 standard.