MAR-M247合金高温断裂机制的原位研究

In-situ study of high temperature fracture mechanism of MAR-M247 alloy

摘要:

利用原位高温拉伸台在扫描电镜中研究了镍基铸造高温合金MAR-M247在室温、400 ℃与760 ℃拉伸过程中的动态组织演变和断裂机制。原位测试结果表明，在室温到760 ℃范围内，MAR-M247合金的屈服强度与抗拉强度随温度的升高略有下降，拉伸塑性略有提高。室温原位拉伸过程中，并没有出现滑移带；400 ℃与760 ℃的原位拉伸，只在样品断口附近存在少量的滑移带。随拉伸温度的提高，合金的断裂机制并无明显变化，均表现为韧性穿晶断裂。合金的微裂纹主要来源于变形过程中碳化物的破裂，晶内与晶界都存在因碳化物破裂而形成的微裂纹。

Abstract:

The dynamic microstructure evolution and fracture mechanism of Ni-based cast superalloy MAR-M247 are investigated during tensile test at room temperature, 400 °C and 760 °C by an in-situ SEM high temperature tensile stage. The in-situ tensile test results show that the yield strength and ultimate tensile strength decrease slightly, and the tensile plasticity increases slightly from room temperature to 760 °C. There is no slip band during in-situ tensile test at room temperature; and there is only a small amount of slip bands near the fracture surface at 400 °C and 760 °C. With the increase of tensile temperature, the fracture mechanism is not change, and all of them are ductile transgranular fracture. Microcracks mainly originate from the rupture of carbides which dispersed in the grains and on the grain boundaries.