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The superficial texture of the material can exert a decisive influence on the application and performance of the machined component. The conventional fluids used in grinding processes are environmental risk and can also be dangerous to the health. The disposal of these toxic fluids is expensive and the contamination in the proximities of the machines can present risks to the health for the personnel in the shop floor. This paper analyzes the performance of the minimum quantity lubricant (MQL) technique and compares it with the conventional cooling method, developing an optimized fluid application method using a specially designed nozzle, through which a minimum amount of oil is sprayed in a compressed air flow. This paper also explores and discusses the concept of the MQL in the grinding process of hardened AISI 4340 steel. The performance of the MQL technique in grinding was evaluated based on an analysis of the surface integrity (roughness, microstructure and microhardness). As a result, it was realized that the MQL technique provides very similar characteristics to conventional process and can be applied in industry, thus contributing to an environment friendly manufacturing.

ResumoOs aços inoxidáveis duplex possuem uma microestrutura austeno-ferrítica com fração média de cada fase de cerca 50%. A microestrutura duplex é responsável por melhorar as propriedades mecânicas do material. A soldagem destes aços é frequentemente uma operação crítica. O objetivo desse trabalho é analisar a influência do aporte térmico sobre a microestrutura de juntas soldadas do aço duplex SAF2205. As chapas de aço duplex 2205 foram soldadas pelo processo de soldagem GMAW (Gas Metal Arc Welding), variando apenas o aporte térmico. Após essa etapa, as chapas foram cortadas, preparadas para a análise metalográfica, difração de raio X (DRX) e ensaio de microdureza Vickers. As microestruturas do metal base (MB), da zona termicamente afetada (ZTA) e da zona fundida (ZF) foram caracterizadas nesse estudo. Foi verificado que quanto maior o aporte térmico menor a quantidade de ferrita e maior o crescimento de grão da austenita na região fundida. Os ensaios de microdureza mostraram que quanto maior o aporte térmico maior será a ZTA do material. Palavras-chave: Aço duplex; Aporte térmico; GMAW. INFLUENCE OF HEAT INPUT CONTRIBUTION ON THE MICROSTRUCTURE WELDED JOINTS IN STEEL DUPLEX SAF2205 AbstractDuplex stainless steels have an austenitic-ferritic microstructure with an average fraction of each phase of about 50%. The duplex microstructure is responsible for improving the mechanical properties of material. The welding of these steels is often a critical operation. The aim of this study is to analyze the influence of heat input on the microstructure of welded joints of duplex steel SAF2205. The steel sheet duplex 2205 were welded by the welding process GMAW (Gas Metal Arc Welding), varying only the heat input. After this step the sheet were cut and prepared for metallographic analysis, X-ray diffraction (XRD) and Vickers hardness test. The microstructures of the base metal (BM), the heat affected zone (HAZ) and the weld zone (WZ) were characterized in this study. It has been found that the greater heat input the smaller was the amount of ferrite and the increased grain growth of austenite in the melt region. The microhardness tests showed that the higher heat input increased the HAZ material.

ResumoLigas de alumínio possuem, dentre diversas propriedades, uma atrativa combinação entre resistência mecânica e densidade, característica que leva à utilização cada vez maior desses materiais em setores estratégicos, como as indústrias aeronáutica e automobilística. O aumento da resistência dessas ligas, por sua vez, está associado ao tratamento de endurecimento por precipitação, podendo ainda ser influenciado pelo encruamemto do metal, esse último decorrente da eventual realização de deformação plástica entre as etapas de solubilização e envelhecimento do referido processamento. Dentro desse contexto, neste trabalho foi avaliado o comportamento mecânico de amostras da liga de alumínio 7.075 submetidas à compressão monotônica e cíclica após a etapa de solubilização do tratamento de endurecimento por precipitação. O comportamento do material foi analisado através de ensaios de dureza. Os resultados evidenciaram os efeitos das características e da magnitude da deformação na propriedade mecânica da liga. Palavras-chave: Deformação; Endurecimento por precipitação; Liga de alumínio. INFLUENCE OF MONOTONIC AND CYCLIC STRAIN ON THE MECHANICAL BEHAVIOR OF AN ALUMINUM ALLOY SUBMITTED TO PRECIPITATION HARDENING HEAT TREATMENT AbstractAluminum alloys have, among several properties, an attractive combination of strength and density, which leads to an increased use of these materials in strategic sectors, such as aeronautical and automotive industries. The significant increase of strength in these alloys is usually associated with the precipitation hardening heat treatment, and may also be influenced by work hardening, the latter resulting from plastic deformation between the solution treatment and aging. In his study the mechanical behavior of 7075 aluminum alloy samples subjected to monotonic and cyclic compression after solution treatment was evaluated. The behavior of the material was analyzed through hardness tests. The results showed the effects of the characteristics and the magnitude of the strain in the mechanical property of the aluminum alloy.