Solidification Characteristics and Defect Formation Mechanism of the Fourth Generation Ni-Based Single Crystal Superalloy

Solidification characteristics and defect formation mechanism of the fourth generation Ni-based single crystal superalloy were systematically investigated. The results indicated that the solidification path of the experimental superalloy during directional solidification was determined as followed: L → γ → β-NiAl → γ'→ (γ+γ') → TCP. The phase transformation process of the peritecticreaction L + β-NiAl → γ' of the experimental superalloy during directional solidification had been revealed using the planar interface solidification, and the relaxation of some atoms on the matching planes (110)β and (111)γ' maximized the atomic matching at the interface, increasing the possibility of peritectic γ' phase nucleated on primary β-NiAl phase in the peritectic reaction. Finally, it was proposed that it was beneficial to reduce the formation tendency of large-angle grain boundary defects at the platform and reduce the orientation difference of low-angle grain boundaries by controlling secondary dendrite orientation.