Improvement in Mechanical Properties of Titanium Deformed by ECAE Process

Abstract

In this study, annealed CP-Ti (Grade 2) was processed by Equal Channel Angular Extrusion (ECAE) up to 2 passes at a temperature of 400◦C following route A with a constant ram speed of 30 mm/min through a die angle of 90◦ between the die channels. Mechanical properties of the extruded materials were obtained at different strain rates. The results indicated that the tensile yield stress and ultimate tensile strength of the extruded specimens increased significantly after 2 passes of ECAE process. The maximum increase for yield stress was around 90% which occurred at the pulling rate of 0.5 mm/min. The bending fatigue life of the extruded specimens improved significantly so that in low cycle fatigue regime a 700% increase in fatigue life was observed after two ECAE passes. The improvement was lower in high cycle fatigue regime. The microhardness measurement of the specimens indicated that the average microhardness of the samples increased about 140% after 2 passes. The fracture mechanism of the ECAE specimens was also studied by fractography of the fracture surface of specimens. Microstructure of the extruded specimens was also examined by optical microscopy.