Effect Of Rolling Process On Fatigue Behavior Of TC4-DT Alloy Sheets

The effect of rolling process and heat treatment on microstructures and mechanical properties of TC4-DT sheets was systematically investigated by means of optical microscope observation, mechanical property test and scanning electric microscope fractography analysis. The relationship among different kinds of microstructures and properties were analyzed.It was found that bimodal microstructure by solution and ageing treating exhibits higher strength and ductility. The primaryα-phase decreases, strength increases and ductility decreased with the solution temperature increasing when the TC4-DT alloy is heat treated in the two phase region. In addition, the faster the cooling rate, the moreα' phase will be obtained, and the strengthening effect will be increased. With the increase of aging temperature and time, the amount of secondaryα-phase increases and size becomes coarse, the yield strength increases up to the peak and then decreases, but the ductility has a little change. The best heat treatment system is 955℃/1h AC +550℃/8h AC, and the specimen will get a better mechanical properties under the heat treatment.Texture was found in the TC4-DT sheets without cross rolling by X-ray diffraction analysis. The diffraction peaks of (002),(101)and(103)were significantly different from the card. The texture can be reduced by cross rolling. The result of the fatigue test shows that dispersion of the high cycle fatigue behavior of TC4-DT sheets can be improved by cross rolling.