加载速率对TiAl基合金断裂机理的影响

Effect of Loading Rate on Fracture Mechanism of TiAI-Based Alloys

摘要:

通过拉伸断裂、拉伸卸载实验和相应的SEM观察研究了载荷控制下加载速率对具有全层（FL）和双态（DP）组织TiAl基合金断裂机理的影响。结果表明：当加载速率比较小时，微裂纹的面密度较大，即有足够的时间开裂，裂纹沿着晶界或者层间起裂，并且在层团内部基本上沿着层间扩展，基本上没有河流纹走向，沿层断裂面占整个断口的绝大部分，断口上晶粒结构比较明显，对材料性能影响较大：加载速率较大时裂纹没有足够的时间起裂和扩展，因此在断裂时形成很多河流纹走向，而且断口形貌中晶粒结构不明显；由于提前开裂的裂纹很少，所以表现出断面上分布的断裂小面的尺寸较小，从而对材料性能影响较小。

Abstract:

Through tensile test, tensile-unload test and SEM observation, the effects of loading rate on fracture mechanism of TiAl-based alloys with fully lamellar and duplex microstructures were investigated. The result reveals that when the rate is lower, microcrack density is larger and microcracks have sufficient time to initiate along many grain boundaries or lamellar interface, and propagate basically along interlamellar within the grain. There are no river patterns on the fracture surface. A majority of the fracture surface belongs to interlamellar fracture, and grain structure is not obvious on fracture surface, such case effects on the mechanical properties are dominant. While the microcracks have no time to initiate and propagate in the case of high loading rate, many river patterns come into being in the course of fracture, and we can also find the grain structure no longer obvious on the fracture surface. Because many microcracks initiate ahead, the size of fracture facet is smaller, so the effects are much less obvious, in this case.