Abstract
Tailoring high-density annealing twins in laser powder bed fusion(LPBF)-fabricated alloys based on their intrinsic residual stress requires high annealing temperatures and/or long-term annealing,result-ing in the abnormal growth of large recrystallized grains,which is detrimental to mechanical properties.This work proposes a new strategy for achieving a favorable strength-plasticity synergy of the LPBF-fabricated Inconel 718 superalloy by performing a deep cryogenic treatment(DCT)with the subsequent heat treatment(including annealing and double aging)to tailor fine grains with"high-density annealing twins+precipitates"architectures and compares the obtained material with an alloy subjected to a direct heat treatment without a prior DCT.The obtained results reveal that the additional internal stress gen-erated during DCT increases the stored energy and dislocation density,which provide a sufficient driving force for activating high-density annealing twin boundaries(63.2％)with fine grains(31.6 μm)within a short annealing time.The more homogeneous tailored microstructure with the"finer grains+high-density twins+precipitates"architectures decreases the mean free path of slipping dislocations,pro-moting intensive interactions with dislocations and inducing a strong strain hardening effect.The mul-tiple deformation modes of stacking faults coupled with Lomer-Cottrell locks,thin primary deformation twins,and secondary twins activated during tensile loading,sustaining a strong work hardening ability and delaying the plastic instability,which exhibits a high strength(yield strength of 1088 MPa and tensile strength of 1369 MPa)and excellent plasticity(elongation of 30％).This work not only describes a fea-sible method for simultaneously enhancing the strength and plasticity in additively manufactured(AM)alloys but also provides new insights into increasing the fraction of twins at a small grain size to improve the grain boundary-related properties without destroying the AM alloy shape.
基金项目
Program for Industry Support of University in Gansu Province(2023CYZC-28)
Major Science and Technology Projects of Gansu Province(22ZD6GA008)
Key Research and Development Program of Gansu Province(22YF7GA156)
Science Foundation for Youths of Gansu Province(23JRRA772)
Hong Liu Firstclass Discipline Construction Plan of Lanzhou University of Technology()
NETL
NSTL
万方数据