Complex phase steels, known for their high levels of conformability, energy absorption, and deformation capacity, are among the more advanced high-strength steels. The objective of this study was to compare the mechanical properties of CPW 800-class complex phase steels, with and without laser welding. The analysis involved determining tensile strength, yield strength, elongation, and area reduction through tensile tests, in scenarios both with and without laser welding. Additionally, the number of cycles was assessed via fatigue tests, and absorbed energy was measured using impact tests. The non-parametric Kruskal–Wallis test, at a 5% significance level, revealed that tensile strength, yield strength, area reduction, and absorbed energy were statistically similar regardless of laser welding. However, elongation and the number of cycles showed significant differences. The fractured surface from axial fatigue tests exhibited ductile characteristics, with the additional presence of dimples or alveoli.

TRIP (Transformation Induced Plasticity) and DP (Dual-Phase) steels are written in a new series of steels which present excellent mechanical properties. As for microstructure aspect, TRIP steels consist on a ferrite matrix with a second phase dispersion of other constituents, such as bainite, martensite and retained austenite, while dual-phase steels consist on martensite dispersion in a ferrite matrix. In order to identify the different microconstituents present in these materials, microstructure characterization techniques by optical microscopy (using different etchants: LePera, Heat-Tinting and Nital) and scanning electron microscopy were carried out. This being so, microstructures were correlated with mechanical properties of materials, determined by means of tensile tests. It is concluded that steels assisted by TRIP effect have a strength and elongation relation higher than the dual-phase one. With microstructure characterization, it was observed phases present in these materials microstructure.

The performance of multiphase steels is closely related to their microconstituents. Thus, the characterization and effective control of the microstructure of these materials are crucial, and chemical attack processes are essential for this to occur. In this context, this study sought to employ the Taguchi method to evaluate the chemical etching process with the LePera reagent in order to investigate the influence of different process variables, in addition to the interactions between them, on the quality of the image obtained. The variables analyzed were: concentration of picral (CP) and sodium metabisulfite (CSM) solution, pre-attack (PA), drying mode (DM) and attack time (AT). in addition to the relative humidity and temperature of the environment. Therefore, a quality index (QI) was suggested for the images obtained, which, together with the analysis of variance, indicates the best route for microstructural characterization of TRIP800 steel (CP-4.0%; CSM-0.5% ; PA-No; DM-Natural; AT-25s; . Temperature (°C): 15I---25 and Relative humidity (%): 55I---90). In addition to indicating the variables that most influence the process. The influence of noise factors (temperature and relative humidity) was also proven.

The future of the automotive industry appears to hinge on the integration of dissimilar materials, such as aluminum alloys and carbon steel. However, this combination can lead to galvanic corrosion, compromising the structural integrity. In this study, laser-welded joints of 6013-T4 aluminum alloy and DP980 steel were evaluated for their morphology, microhardness, and corrosion resistance. Corrosion resistance was assessed using the electrochemical noise technique over time in 0.1 M Na₂SO₄ and 3.5% NaCl solutions. The wavelet function was applied to remove the DC trend, and energy diagrams were generated to identify the type of corrosive process occurring on the electrodes. Corrosion on the electrodes was also monitored using photomicrographic images. Analysis revealed an aluminum–steel mixture in the melting zone, along with the presence of AlFe, AlFe₃, and AlI₃Fe₄ intermetallic compounds. The highest Vickers microhardness was observed in the heat-affected zone, adjacent to the melt zone, where a martensitic microstructure was identified. The 6013-T4 aluminum alloy demonstrated the highest corrosion resistance in both media. Conversely, the electrochemical noise resistance was similar for the DP980 steel and the weld bead, indicating that the laser welding process does not significantly impact this property. The energy diagrams showed that localized pitting corrosion was the predominant form of corrosion. However, generalized and mixed corrosion were also observed, which corroborated the macroscopic analysis of the electrodes.

RESUMO O setor ferroviário sempre tem estado em busca de um aumento do rendimento de seus produtos envolvidos no transporte de cargas e passageiros. Uma das formas de aumentar a eficiência deste tipo de transporte se baseia no aumento da velocidade dos trens e das cargas transportadas por eixo, o que torna as ferrovias mais competitivas. No entanto, estas soluções geram elevadas tensões nas rodas ferroviárias aumentando assim a possibilidade de ocorrerem falhas por fadiga nas mesmas. Neste contexto, o objetivo deste trabalho é avaliar as propriedades mecânicas, incluindo fadiga, e as características microestruturais dos materiais utilizados na fabricação de rodas ferroviárias. Foram avaliados três materiais diferentes (Aço carbono – amostra fundida e forjada; Aço Microligado – amostra forjada) utilizados neste segmento através de ensaio microestrutural, tração, tenacidade à fratura e fadiga, sendo uma roda fabricada por forjamento e com aço classe “C” (0,7% C), uma fabricada por fundição com o mesmo material e outra roda forjada produzida com o aço classe “C” desgaseificado à vácuo e microligado com nióbio e molibdênio. Os resultados dos ensaios indicam que a roda forjada e microligada apresentou valores superiores das propriedades mecânicas quando comparado aos demais materiais estudados. Além disso, o processo de fabricação por forjamento apresentou melhores resultados quando comparado ao processo de fundição.

O interesse no estudo da corrosão não envolve apenas o campo científico, mas também o campo econômico e ambiental. Nesta situação os inibidores de corrosão à base de extratos vegetais surgem como novas alternativas por serem de fontes renováveis e baixo custo. Em vista disso, a proposta deste trabalho é realizar, com auxílio do Método de Taguchi e Análise da Variância, a avaliação da influência das variáveis e suas interações envolvidas no processo de corrosão através do ensaio de perda de massa utilizando como inibidor vegetal o casquilho de guaraná. Para tanto, foi selecionado o arranjo ortogonal L16 e os fatores analisados em dois níveis: Inibidor vegetal, temperatura, meio ácido, tempo de imersão, e material. A variável resposta dos experimentos realizados foi a perda de massa das amostras. Com os resultados obtidos conclui-se que o casquilho de guaraná tem grande potencial pra utilização como inibidor de corrosão vegetal. Através da avaliação da resposta obtido no Método de Taguchi, verificou-se também que o fator mais significativo do processo de corrosão em ensaio gravimétrico é o meio ácido seguido da temperatura do meio e não há interação entre os fatores.