Effect Of Solution And Aging On Microstructure,Mechanical Properties And Texture Of Hot-rolled TC18Titanium Alloy

Near-β titanium alloy TC18possessed many advantages such as high tensile strength, high toughness, good hardenability etc. It was widely used in the aerospace industry as airframe load-carrying members. Through current heat treatment process, the well match of strength, toughness and ductility could not be achieved since the microstructure was hard to control efficiently. Also, the revolution of texture during heat treatment was seldom discussed. Considering the problems above, this paper used orthogonal experiment method for design of heat treatment experiment, which was based on solution treated and aged process. In this experiment, the parameters such as temperature, time and cooling method were considered, Scanning electron microscope, Electronic back-scattered diffraction and Mechanical properties testing machine were used, and the effect of heat treatment parameters on microstructure and mechanical properties as well as the revolution of texture during solution treated and aged process were researched. The main conclusions were as follows:1) For parameters in this heat treatment, the main factors for elongation were solution temperature, cooling method and aging temperature, while the main factors of tensile strength were aging temperature and cooling method.2) During the solution and aging of hot-rolled TC18alloy, the decrease of solution temperature and cooling rate, or the increase of aging temperature both prompted the precipitation of α adhere to equiaxed α, led the content and size of equiaxed α rose, thus improved the elongation of TC18alloy. During the same process, the decrease of aging temperature and the increase of cooling rate both prompted the precipitation of acicular α inside of β grains, which improved the tensile strength of TC18alloy.3) During solution at820℃-730℃of hot-rolled TC18alloy, only recovery and phase transformation occurred in β phase, and the type of texture of P phase remained the same while the intensity of texture decrease a little with the decrease of solution temperature, which was due to phase transformation of βâ†'α. On the other hand, during solution at820℃-730℃, recovery, phase transformation and recrystallization all occurred in a phase, which led the texture change of a. The texture of a phase solution treated at820℃was parallel to the rolling direction (RD). With the decrease of solution temperature, phase transformation intensified and the degree of recrystallization reduced, which led the change of texture from parallel to the combination of RD to parallel to RD, parallel to TD and45°to RD and TD. Meanwhile, the intensity of recrystallization texture of<2-1-10>//ND and<10-10>//TD decreased.