TC21钛合金的全片层组织和冲击性能研究

Study on Multi-level Full Lamellar Structure and Impact Properties of TC21 Titanium Alloy

摘要:

利用光学显微镜、场发射扫描电镜和示波冲击试验机等研究了TC21钛合金在不同退火温度下的全片层组织演化规律和冲击韧性。结果表明：TC21钛合金经980 ℃固溶处理后，再经720、770、820 ℃退火处理，均能获得具有多层次特征的全片层组织。随着退火温度升高，TC21钛合金组织中α片层厚度、晶界α相厚度、α丛域尺寸都增大，而β晶粒尺寸基本保持不变。合金显微组织中小角度界面的比例随退火温度的升高而逐渐增加，冲击断裂过程中的裂纹形成功和扩展功也逐渐增大，且扩展功所占比例提高；断裂机制从穿晶断裂为主逐渐向沿晶界和丛域界断裂为主转变。

Abstract:

The full lamellar structure evolution and impact toughness of TC21 titanium alloy were studied by using optical microscope(OM), field emission scanning electron microscopy(FESEM) and instrumented charpy impact testing machine under different annealing temperatures. The results show that multi-level full lamellar structure can be obtained when TC21 titanium alloys are annealed at 720 ℃, 770 ℃ and 820 ℃ after solution treatment at 980 ℃. Additionally, the thickness of α platelets and grain boundary α phase, as well as the size of α colonies increase with the increase of annealing temperature, while the size of β grain remains unchanged. Moreover, the fraction of low angle boundaries increases also in the multi-level microstructure as increasing annealing temperature, resulting in the increase in crack initiation energy and crack propagation energy of TC21 titanium alloy during impact test, as well as the fraction of crack propagation energy increasing. With the increase of annealing temperature, the fracture mechanism gradually changes from transgranular to intergranular and along colony boundary.