한국주조공학회

The tensile properties of the single crystal superalloy CMSX-4 were examined at various temperatures. In the heat-treated state, some portion of the eutectic γ-γ΄ remained, and a uniform cuboidal γ΄ particles existed across the entire material. The yield strength and tensile strength reached highest at 750oC and decreased with raising testing temperature. The elongation was lowest at 650oC due to concentrated deformation near the fracture area. However, the elongation increased at higher temperatures due to uniform deformation throughout the entire specimen. Fracture surface analysis tested at 850oC and 950oC revealed that cracks originated from casting defects. TEM observations conducted after the tensile test indicated that the primary deformation mechanism at room temperature involved dislocation shearing within the γ΄ phase. However, the increased strength both at 750oC where stacking faults generated and at 650oC was caused by the increased resistance of γ΄ phase to dislocation. The strength decreased because the movement of dislocations became easier due to the thermal activation process at and above 850oC.

Single crystal superalloy, CMSX-4, Tensile property, Dislocation.