等通道转角挤压工艺对TA15合金显微硬度的影响

Effects of Equal Channel Angular Pressing on Microhardness of TA15 Alloy

摘要:

研究近α钛合金TA15经等通道转角挤压工艺（ECAP）加工后的维氏显微硬度及其变化规律。结果表明：TA15合金经ECAP挤压后，显微硬度显著提高，且合金试样外层硬度略高于芯部。合金的显微硬度与组织畸变程度、位错密度、晶粒尺寸以及相组成等密切相关。相变点以下挤压，挤压温度越低，硬度越高；相变点以上挤压，由于挤压后水冷过程中在β相内产生针状马氏体α′，硬度明显高于相变点以下挤压。模具转角越小，显微硬度越高。随挤压次数增加，硬度先增大后保持基本不变，而挤压路径对硬度的影响与挤压次数、挤压后细化效果密切相关。TA15合金经ECAP后退火，显微硬度明显降低

Abstract:

Vickers microhardness of TA15 titanium alloy after equal channel angular pressing (ECAP) and its variation was investigated. The results indicate that the microhardness is increased observably after ECAP, and the microhardness level of the outer layer is slightly higher than that of the core in the same cylinder sample. The microhardness of ECAPed alloy is closely related to microstructure distortion, dislocation density, grain size and phase composition. There is a decrease in microhardness with the increasing pressing temperature below Tβ. As a result of the acicular martensite precipitation, the microhardness after ECAP above Tβ is much higher than that below Tβ. A lower die angle means a better hardness. The microhardness increases first and then remains at a certain level with the increasing passes, while the route effects on hardness are related to the pass number and the refinement effects. The annealing after ECAP can effectively reduce the microhardness