Investigation On Low Temperature Upsetting Deformation Behavior Of TC4 Titanium Alloy

Fastening parts are widely applied in machine. Titanium alloy is used in various fields as its excellent combinationproperty. At present, TC4 Titanium alloy is the most useful alloy for titanium. Therefore, low temperature processability of TC4 titanium alloy will be researched in this work.In this text, upsetting deformation behavior of TC4 alloy is researched for grain sizes of 2μm and 9μm, which include dynamic upsetting at room temperature and quasi-static upsetting at different temperatures. True stress and stain behavior are researched at the same time phase composition and microscopic-structure are studied by OM, XRD, TEM, SEM etc.The results of the tests showed that:While TC4 sample is upsetting, drum appeared in the waist of the sample. As the grain size grown, the deformation limit diminished and the drum was more severe. As the friction force reduced, the deformation limit lessened. Height-diameter ratio had nothing to do with deformation behavior. After the deformation, there was not new phase appear. The deformation mechanism of phase a is dislocation and twinning, phaseβis slippage. The macrography fracture was present as 45°angle. The fracture was made up of brittlefracture and ductilefracture. As the grain size diminished, the ductilefracture scale increase and the size of dimple amplify.At room temperature, the flow stress curve appeared the type of work hardening and no new phase appeared. The deform mechanism is dislocation, slippage and twinning, accompanied smashing. When deformed at 350℃, the flow stress curve appeared the type of work hardening for high strain rate, and type of dynamic recovery for low strain rate. There was no phase changed. The main deform mechanism is dislocation and slippage, the dislocation mechanism included grain glide and grain roll. At low strain rate, the dislocation in phase a is diminish, which show the character of dynamic recovery. When deformed at 700℃, phase a decreased and phaseβincreased. At high strain rate, the flow stress curve appeared the type of dynamic recovery; at low strain rate, the flow stress curve appeared the type of dynamic recrystallization. The soften mechanism were dynamic recrystallization in phase a and dynamic recovery in phaseβ..