Luiz Paulo Mendonça Brandão

Influence of grain size and additions of Al and Mn on the magnetic properties of non-oriented electrical steels with 3 wt. (%) Si

The influence of hot-band grain size and additions of aluminum and manganese on the magnetic properties of non-oriented grain (NOG) low-carbon electrical steel with about 3 wt. (%) Si were investigated using optical microscopy and X ray diffraction. The addition of manganese resulted in larger grains after final annealing. Coarse grains in the hot-band and addition of Mn led to a Goss orientation component after final annealing, which resulted in an increase in the magnetic permeability.

Dislocation Density by X-ray Diffraction in α Brass Deformed by Rolling and ECAE

Dislocations are responsible for most aspects of plastic deformation in metals. In this work, the dislocation density, ρ, in brass was estimated after different deformation processes via line broadening of X-ray diffractograms using the Convolutional Multiple Whole Profile Program (CMWP) and by Transmission Electron Microscopy (TEM). In addition, we attempted to evaluate, on a global basis, the influence of crystallographic texture in ρ analysis, making sure that the results obtained by XRD could be trusted even in samples with moderate levels of texture. For this, we compared the ρ values for α brass samples (66% Cu and 34% Zn) with different levels of texture, one deformed by cold rolling and the other by equal channel angular extrusion (ECAE).The results suggest that using CMWP program it was possible to satisfactorily estimate the dislocation density in α brass. It also the was shown that the results by XRD and by TEM were self-consistent in two samples texturized to different degrees.

Properties of NGO 3% Silicon Steel Asymmetrically Cold Rolled

The effects of asymmetric and conventional deformations and annealing on the microstructure of non-grain-oriented (NGO) 3 wt% silicon steel were analyzed by x-ray diffraction, optical microscopy and magnetometry. The results suggest that pure asymmetric rolling tends to lessen magnetic losses. However, intermediate annealing resulted in lower planar anisotropy, which could be estimated from the magnetic anisotropy theory. In this work, it was shown that this theory is able to predict the J50 magnetic polarization values using crystallographic texture.

The Influence of Sample Preparation on the Quantitative Analysis of the Volume Fraction of Martensite Formed in a 304l Trip Steel

The metastable 304L austenitic stainless steels are susceptible to phase transformation induced by plastic deformation. The traditional metallographic preparation, via mechanical methods, introduces superficial plastic deformation from grinding and polishing. It is important to evaluate this effect on the results of quantitative analysis of martensite formed in 304L steels and similar alloys. In this work, phase transformation was induced by a tensile test at room temperature with two different plastic deformation rates in order to provide distinct structural conditions for the proposed analysis. X-ray Diffraction (XRD) and Ferritescopy were used to determine the volume fraction of martensite in samples with and without metallographic preparation. The results show that the analyses quantitative were not affected by metallographic preparation.

Evaluation of the Relationship between Crystallographic Texture and Magnetic Properties through the Magnetocrystalline Anisotropy Coefficient

It is well known that iron has a magnetocrystalline anisotropy and, therefore, the crystallographic texture has great influence on its magnetic properties. In most applications of non-oriented grain electrical steels, it is desirable that the magnetic properties are isotropic. In this work, modern quantitative texture analysis methods are used to characterize the crystallographic textures of many types of non-oriented grain electrical steels and their relation with the magnetic properties. The magnetocrystalline anisotropy coefficient is the parameter of texture analysis that is directly related to the magnetic properties. This paper analyzes the correlation between the magnetic properties of electrical steels with 3 wt.% to 5 wt.% silicon and their magnetocrystalline anisotropy coefficients.

Residual Stress and Texture Evolution on Surface of 304L TRIP Steel Sheet Subjected to FLC Test

The martensite formation in the outer and inner blank sheet surfaces of the metastable 304L austenitic stainless steel subjected to the Forming Limit Curve (FLC) testing, performed according to the Marciniak method, was analysed in regions located near and away from the failure site. X-ray Diffraction (XRD) was also used for residual stress and texture quantification related to strain-induced martensitic phase transformation resulting from distinct stress and strain trajectories associated to FLC specimens. From the results were observed some aspects as greater diversity in the martensite formation and austenite hardening at outer sheet surface that are correlated to residual stress and austenite textural evolution.

PRODUÇÃO E CARACTERIZAÇÃO DO MICROCOMPÓSITO DE Cu/NbTi

Vivian Reis Corrêa Talita Gama de Sousa 2 Luiz Paulo Mendonça Brandão 3 Resumo Determinadas aplicações de magnetos pulsados ocorrem sob a ação de campos magnéticos elevados, (≥ 100 T). Esses campos provocam efeitos tais como, elevadas tensões tangenciais (hoop stress) produzidas pela força de Lorentz e conversão de parte da energia elétrica em calor (efeito Joule) que deterioram o material. Assim uma combinação de alta resistência mecânica (> 1 GPa) e alta condutividade elétrica (mínimo de 70% IACS International Annealed Copper Standard) é necessária por parte destes materiais. No presente trabalho, foram desenvolvidos fios condutores para possível utilização em magnetos pulsados. O cobre e a liga nióbio-titânio foram escolhidos por possuírem boa condutividade elétrica e boa resistência mecânica, respectivamente; além de serem imiscíveis na temperatura ambiente. Inicialmente foram utilizados fios de cobre puro e Cu/NbTi, os quais foram convertidos em fios por trefilação. Após o processamento, os fios foram introduzidos em tarugos de cobre OFHC (Oxigen Free High Conductivity) e reprocessados. Foram produzidos 2 compósitos variando os tratamentos térmicos. Os compósitos obtiveram uma satisfatória interação matriz/filamento, o que melhor combinou propriedades mecânicas e elétricas foi o que atingiu limite de resistência de 547,8 MPa e condutividade 85,98% IACS. Palavras-chave: Alta resistência mecânica; Alta condutividade elétrica; Alta deformação plástica; microcompósitos Cu/NbTi.

COMPÓSITOS COBRE-GRAFENO PRODUZIDOS POR METALURGIA DO PÓ COM COMPACTAÇÃO A FRIO

Resumo Foram fabricados compósitos de matriz de cobre, reforçados com grafeno a partir da mistura de uma dispersão de óxido de grafeno com pó de cobre eletrolítico. A dispersão foi produzida pelo método de Hummers modificado e caracterizada por espectroscopia Raman e difração de raios X. Os compósitos foram fabricados pelo processo de metalurgia do pó convencional. Os pós de compósitos foram caracterizados por microscopia eletrônica de varredura, os corpos de prova consolidados foram avaliados quanto a densificação a verde e do corpo sinterizado, e os corpos sinterizados foram submetidos a ensaio de compressão a fim de verificar a resistência dos compósitos. Palavras-chave: Óxido de grafeno; Compósitos de matriz metálica; Metalurgia do pó.

Mechanical Properties and Crystallographic Texture of Symmetrical and Asymmetrical Cold Rolled IF Steels

The crystallographic texture developed during cold rolling and subsequent annealing of interstitial free sheet steels aims to increase conformability. For this, it is necessary to obtain partial α-fiber and continuous and homogeneous γ-fiber texture components. In this work, the influence of symmetric (SR) and asymmetric (AR) cold rolling on crystallographic texture and mechanical properties of an interstitial free steel (IF) was investigated. Symmetric cold rolling yields α- and γ-fibers, which are enhanced as deformation increases. Moreover, α-fiber weakening occurs due to recrystallizations, improving formability. The same fibers are produced by asymmetric cold rolling, but in this case, the γ-fiber is slightly shifted in psi, which is one of Euler angles second ROEs notation1,2, and more homogeneous than in symmetric rolling. The best mechanical properties were achieved by asymmetric cold rolling/annealed with about 80% deformation.

Residual Stress Evaluation by X-Ray Diffraction and Hole-Drilling in an API 5L X70 Steel Pipe Bent by Hot Induction

The API 5L X70 steel is used in high-pressure gas transmission pipelines. Because of this, knowledge of presence of residual stress and their magnitude is important to assess the material integrity in service. For the pipeline manufacturing, tubes need to be curved which is often made using the hot induction bending process. This process can introduce different residual stress depending of tube position. For this research, in order to evaluate the residual stress, was used an API 5L X70 tube that was previously curved by hot induction process. Samples were taken from the extrados, intrados, neutral line and straight section of the curved tube. Residual stresses were studied by two conventional methods: X-Ray Diffraction (XRD) and Hole-Drilling, which are destructive and non-destructive methods, respectively, in order to assess their qualitative responses. Each of these methods presents particular methodologies in sample preparation and material analysis, but also they differ in factors such time consumption and cost of the analysis. The qualitative responses obtained by the two different methods were comparable and satisfactory and pointed out the existence of a compressive residual stress state in steel pipe.