High Temperature Low Cycle Fatigue and Cyclic Constitutive Relation of MAR-M247 Directionally Solidified Superalloy

This paper investigates the effect of solidification direction on cyclic constitutive relation and low cycle fatigue life for a directionally solidified (DS) superalloy Mar-M247LC at 1173 K in air. Strain controlled push-pull low cycle fatigue tests were carried out for three kinds of specimens of which loading direction was 0, 45 and 90 deg to DS axis. The 0 deg specimen exhibited the largest fatigue strength, the 45 deg specimen the smallest and the 90 deg specimen the intermediate. The difference in the fatigue strength due to the loading direction was discussed in detail from the viewpoint of the anisotropy of Young’s modulus. A life prediction method for DS specimens, considering the anisotropy of the Young’s modulus, was proposed and successfully applied to the low cycle fatigue data.