Ti-47Al-2Mn-2Nb合金动态拉伸性能的研究

DYNAMIC TENSILE PROPERTIES OF Ti-47Al-2Mn-2Nb ALLOY

采用自制的Hopkinson拉杆装置，在20—1000s－1应变速率范围内研究了具有近全片层组织的Ti－47Al—2Mn—2Nb合金的拉伸力学性能，并与准静态拉伸性能相比较试验发现动态强度明显高于静态强度，前者和应变速率之间遵循线性关系，后者和应变速率之间遵循半对数线性关系；室温塑性随应变速率变化而波动，但变化范围不大.扫描电镜断口分析结果表明，动态与静态断裂方式都以穿晶解理为主，局部区域伴有沿晶开裂.

Room-temperature tensile properties of Ti-47Al-2Mn-2Nb alloy with near lamellar (NL) microstructures were investigated at the strain rates between 20 and 1000 s-1 using a self-designed Split-Hopkinson tensile bar setup with a rotating disk. And a comparison was made between static and dynamic tensile properties. It was found that tensile ductility fluctuates within a narrow range with the variation of the strain rate f dynamic elongation is almost the same as the static elongation. But dynamic strengths (d) of the alloy and their strain rate sensitivity are obviously higher than those under static strain rates, and there exists linear relationship between static strength (s) and the logarithm of the strain rate(s= A + Blu), and between d and the strain rate itself(d = C + D). Fractography analysis indicates that the alloy fractures in a mixed mode of predominant transgranular cleavage and minor intergranular cracking under static and dynamic strain rates. Environmental effect is excluded from the main cause for the room-temperature brittleness of the investigated alloy.