RESUMO Nesta pesquisa foi avaliado o efeito da adição de três tipos de escória de fornos cubilô na deformação a quente de núcleos de areia. Além da avaliação de distorção a quente, foram avaliadas propriedades como resistência a tração imediata e resistência a tração após 30 minutos. Comparativamente, avaliou-se para cada tipo de escória, misturas com a adição 8, 12, 20, 40 e 70% em peso de escória sobre uma areia de sílica da região sul do Brasil. Os resultados mostraram uma redução na resistência à tração imediata dos núcleos de areia, independente do tipo de escória utilizada. A adição de escória granulada de cubilô, devidamente processadas, reduziu a deformação máxima a quente dos núcleos de areia, observou-se também que deformação foi diferente para cada tipo de escória utilizada. De uma maneira geral, os melhores resultados de deformação máxima foram obtidos para as misturas com 70% de adição, seguidas das misturas com 40% de escória. A adição progressiva das escórias também reduz a taxa de deformação, sendo que as escórias verde e preta apresentaram redução de 58%. Os resultados obtidos no ensaio de distorção a quente mostraram um potencial de utilização da escória de cubilô para melhorar o desempenho dos núcleos de areia em relação a defeitos motivados pela expansão da areia de sílica. 3 minutos Comparativamente avaliouse avaliou se 8 12 20 4 70 Brasil utilizada processadas observouse observou geral 58 58% 1 2 7 5

ABSTRACT In this research, the effect of adding three types of cupola furnace slag in sand was evaluated on the hot distortion test. In addition, properties like as immediate tensile strength and tensile strength after 30 minutes were evaluated. Comparatively, mixtures with the addition of 8, 12, 20, 40 and 70% by weight of slag on silica sand from southern Brazil were evaluated for each type of slag. The results showed a reduction in the immediate tensile strength of the sand cores, regardless of the type of slag used. The addition of granulated cupola slag, duly processed, reduced the maximum hot deformation of the sand cores. It was also observed that the deformation was different for each type of slag used. In general, the best maximum deformation results were obtained for mixtures with 70% addition, followed by mixtures with 40% slag. The progressive addition of slag also reduces the deformation rate, with the green and black slag showing a 58% reduction. The results obtained in the hot distortion test showed a potential use of cupola slag to improve the performance of sand cores in relation to defects caused by the expansion of silica sand. research 3 Comparatively 8 12 20 4 70 used processed general rate 58 1 2 7 5

Abstract The exact calculations of the stress and strain distributions based on the controlling equations for a forming process with large deformation are often difficult. To circumvent such difficulties, some analytical methods such upper-bound analysis and slip-line field theory have been established by making a number of simplifying assumptions regarding the material properties and deformation modes. In this work an analytical model based on the upper-bound theory was successfully developed to predict material flow pattern and maximum process loads for an Equal Channel Angular Pressing (ECAP) die with circular cross-section and an intersecting channel angle of 120°. Based on the model, the power dissipated on all frictional and velocity discontinuity surfaces were determined and optimized in order predict the maximum process force as function of the channel geometry and the material plastic behavior. To validate the developed model, the ECAP die were produced and used to determine experimental load-displacement curves of AA6061-T6 specimens with different lengths. A good correlation between theoretical and experimental results was observed. In addition, the constant friction factor demonstrated to have a strong effect on the relative extrusion pressure.

In this work, theoretical composition design and thermo-mechanical treatments were combined in order to improve the mechanical compatibility of a biomedical β-type titanium alloy. By applying a composition design theory, cold rolling and low temperature aging, a metastable β-type Ti-35Nb-7Zr-5Ta (wt%) alloy with an elastic modulus of 47 GPa and a yield strength of 730 MPa was successfully fabricated. This combination of high yield strength and low elastic modulus resulted in enhanced elastic recoverable strain of 1.7%, which is much higher than that of the conventional metallic biomaterials. The microstructure responsible for the much sought-after mechanical properties was observed to be mainly consisted of a homogeneous distribution of nanometer-sized ω- and α-precipitates in a β-phase matrix obtained via cold rolling plus short-time aging at low temperature, i.e. aging at 673 K for 20 min. These precipitates increase the strength of the material by hindering the motion of dislocations while the β-matrix with relatively low content of β-stabilizers gives rise to the observed low elastic modulus. By extending aging time, a higher strength is reached at the expense of an undesirable increasing in elastic modulus.

Resumo O presente trabalho consiste na investigação dos parâmetros de soldagem a ponto por fricção (FSpW) – velocidade de rotação (VR), tempo de soldagem (TS) e profundidade de penetração (PP) – de chapas de AA2198-T8 com 1,6 mm de espessura. O estudo foi realizado com base em ensaios mecânicos de cisalhamento das juntas sobrepostas soldadas nas condições indicadas pelo método Taguchi, visando à determinação da condição ótima de soldagem do ponto de vista de propriedades mecânicas e de processo. Os resultados obtidos indicaram que todas as condições de soldagem avaliadas excedem o limite de carga em cisalhamento mínimo requerido para aplicação aeronáutica. A análise também apontou que as variáveis VR e PP são responsáveis por quase 90% da variação da carga de cisalhamento das juntas, enquanto a contribuição do TS mostrou-se consideravelmente menos significativa. Por fim, a condição ótima de soldagem foi encontrada para os valores mais altos de VR e PP, considerando-se os intervalos dos parâmetros empregados no estudo.

Abstract This work features the investigation of the refill friction stir spot welding (RFSSW) parameters – rotational speed (RS), welding time (WT) and plunge depth (PD) – of AA2198-T8 1.6-mm thick sheets. The study was performed based on lap shear strength tests of overlapped joints welded under conditions indicated by the Taguchi method in order to determinate the optimized combination of parameters, considering the mechanical properties and process conditions. Results based on mechanical testing indicate that all the welding conditions evaluated in the current study exceed the minimum criterion for lap shear strength required for aeronautic applications. RS and PD have shown to be responsible altogether for almost 90% of the welds’ lap shear strength variation, while TS presents considerable less significant contribution to the joints’ resistance. The optimized welding condition was found for highest RS and PD levels and lowest TS.

Friction Stir Welding (FSW) joints of AISI 304 austenitic stainless steel (304 SS) using position controlled mode were investigated in order to understand and relate axial force behavior to welding quality. Joints were produced using two tools and four combinations of specific parameters. The results showed coherence between the axial force profiles and the low-magnification overviews of the welded joints. For defect-free joints, only a natural oscillation on axial force occurred after tool plunge. In contrast, abnormal or abrupt oscillations were directly associated with common welding defects, such as voids and nugget collapse.