Estudo do comportamento em fadiga de alto ciclo da liga Ti-13V-11Cr-3AI

Abstract

Estudo do comportamento em fadiga de alto ciclo da liga Ti -13V -11Cr -3Al The Ti- alloys are a promising group of titanium alloys in terms of processing, properties and potential applications. In order to achieve the optimum balance between strength and toughness it is necessary, besides determining a proper composition in the alloy design, to obtain suitable microstructures by means of thermo-mechanical process and heat treatment. This study aimed to assess the high cycle fatigue behavior of Ti-13V-11Cr-3Al alloy, a high-strength alloy intended for use in the aerospace industry. The material was received in the form of bars with 7.6 mm in diameter, whose microstructure comprises elongated grains and whose mechanical properties combines high tensile strength (1,479 MPa), and reasonable ductility (true strain fracture equal to 0.217). The material was heat treated in two conditions: vacuum annealing at 750C for 1 h with slow cooling, and flash 650C salt bath for 6 min with subsequent water quenching. The study was based on obtaining  / N curves through by rotary bending (R = -1) fatigue tests employing cantilever beam specimens. For each microstructural condition, two  / N curves were obtained, the former with smooth samples and the latter employing specimens with geometric stress concentrators (notches), to evaluate the notch sensitivity of this alloy in both microstructural conditions. The material subjected to flash treatment showed greater dispersion and lower fatigue strength compared to annealed; however also showed lower notch sensitivity at long life (10 6 cycles). The study was complemented by fractographics analysis to identify the fracture initiation points. LORENA