E. Garcia-Sanchez

Note: A method for minimizing oxide formation during elevated temperature nanoindentation.

A standardized method to protect metallic samples and minimize oxide formation during elevated-temperature nanoindentation was adapted to a commercial instrument. Nanoindentation was performed on Al (100), Cu (100), and W (100) single crystals submerged in vacuum oil at 200 °C, while the surface morphology and oxidation was carefully monitored using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The results were compared to room temperature and 200 °C nanoindentation tests performed without oil, in order to evaluate the feasibility of using the oil as a protective medium. Extensive surface characterization demonstrated that this methodology is effective for nanoscale testing.

Optimization of the Severe Plastic Deformation Processes for the Grain Refinement of Al6060 Alloy Using 3D FEM Analysis

An analysis in 3D by means of the finite element method was carried out to study three processes for producing bulk fine-grained materials: dual equal channel angular pressing (DECAP), equal channel angular pressing, and multi-axial forging. For this purpose, a commercial Al6060 alloy in solution heat treatment conditions was utilized. The effect of different values of the coefficients of friction (μ), the plastic flow, the strain hardening behavior, and the effective strain were analyzed. The results obtained from the simulation are in good agreement with the experimental studies. The results indicate that the DECAP process improves the plastic flow and promotes homogeneous strain distribution and grain refinement due to an increase in components of the shear deformation, back-pressure effect, and the diminution of the coefficient of friction.

Microstructure and Mechanical Properties of a Tempered High Cr Martensitic Steel

Microstructural and mechanical studies have been performed in a high Cr martensitic steel Firth-Vickers (FV535) to analyze the tempering of martensite. Nanoindentation technique was used to determine the hardness and elastic modulus through systematic measurements on martensite and tempered martensite. On the other hand, microscopic studies were carried out to analyze the material in the same condition as received and subsequently observe the microstructural modifications after heat treatment. The precipitation presented in the last stage of tempering was observed by transmission electron microscopy. The results showed the effect of the martensite decomposition on the mechanical and nanomechanical properties of FV535.

Study of Decomposition of Martensite in FV535 Steel

The decomposition of martensite and precipitation presented during this process in the FV535 high-chromium martensitic steel and the effect on mechanical properties were studied. FV535 steel is used in petrochemical plants, gas turbine engineering, aircraft, and aerospace industries. The decomposition of martensite has been divided in six different stages, occurring at different temperature ranges, which can vary depending on the steel composition and microstructure; these stages were analyzed by DSC, and in order to analyze the change in mechanical properties, the FV535 steel was characterized by microhardness tests. The precipitation phenomena that occurred in this type of steel were analyzed by DSC and transmission electron microscopy and were correlated with the change in mechanical properties at high temperatures.