Search Results

Materials with appropriate behavior at high temperatures and aggressive environments have become a scientific and technological necessity nowadays. Studies have been undertaken for improvement in getting new alloys, especially for the reevaluation of existing commercial alloys, through the acquisition of data under conditions of higher severity. In this context it was used for this work to Ti-6Al-4V in the form of cylindrical bars, provided forged and annealed at 190°C for 6 hours and cooled in air, which has favorable properties for aerospace application. The alloy after heat treatments to obtain the bimodal structures, martensite and Widmanstätten was subjected to creep tests at 600°C under the conditions of 250 and 319 MPa, in the form of constant load. The structures of Widmanstätten and martensite showed higher creep resistance in both stress conditions used in the trials.

In the present work we study the static indentation, i.e., the formation of small dents which result from laboratory tests specifically developed with this purpose. A mathematical model will be presented. It is based on the numerical and experimental tests performed with previous adjustment of all the mechanical variables involved. This model considers the test specimen and indentator geometry, the sheet anisotropic condition, the sheet's plasticity, and the contact conditions between the plate and the indentator developed. There is a goal to satisfy: specific requirements of a consumer market which is continuously willing for the development of materials with thinner thickness and better mechanical properties. To reach this goal, high strength steels manufactured by the SCAL (Sheet Continuous Annealing Line) are already been produced and tested in experimental scale. These bake-hardening steels can be used to manufacture external panels in the automobile industry.

In this work five methods of heat treatments are investigated in order to obtained convenient volume fractions of ferrite, bainite, martensite and retained austenite, starting with a low carbon steel and seeking the distinction of the phases, through optical microscopy. Specific chemical etching is improved. The results in tensile and fatigue tests were accomplished and the results were related with the microstructural parameters. The results show that the mechanical properties are closely related with the phases, grains size and the phases morphology.