Effects of low temperature annealing on microstructure and residual stress of René104Sc nickel-base superalloy fabricated by laser powder bed fusion
Residual stress in additive manufacturing can cause deformation or even cracking of as-built parts,seriously reducing mechanical properties.In this paper,the microstructure evolution and its effect on residual stress of laser powder bed fusion fabricated René104Sc nickel-base superalloy during low temperature annealing were systematically observed.The results show that after annealing treatment,the cellular structure disappears,the texture strength decreases,the microstructure becomes more uniform and the residual stress is released.After annealing at 500 and 600℃,the microstructure has no obvious change and the residual stress decreases slightly.After annealing at 800℃,the residual stress in sample center decreases from 63 MPa to 21 MPa,and a large amount of γ′ phase precipitates in the alloy,resulting in brittle fracture and elongation decreases from(25.2±2.6)%to(4.7±1.6)%.After annealing at 700℃,the alloy undergoes partial recrystallization,the residual compressive in sample center decreases from 63 MPa to 29 MPa,and its comprehensive mechanical properties are the best with hardness(HV0.3)and tensile strength of 499±4 and(1 461±7)MPa,respectively,which are 18%and 56%higher than that as-built one(423±9,(935±25)MPa).The results provide an effective way to eliminate the residual stress in the additive manufacturing nickel-base superalloy parts and prevent cracking in the storage or post heat treatment process.
laser powder bed fusionlow temperature annealingmicrostructureresidual stressmechanical property
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