Abstract
The microstructure evolution and micromechanical behaviors of additively manufactured 18Ni300 marag-ing steel for both as-printed and aged one were investigated using the in situ high-energy X-ray diffrac-tion(HE-XRD)technique with uniaxial tensile tests.The investigations revealed that the volume frac-tion of reversed austenite increased as the annealing temperature rose.The maraging steel was strength-ened by η-Ni3Ti precipitates,where the aged maraging steel had a higher UTS value of～1860 MPa than～1135 MPa in the as-printed one,but sacrificed more than half of ductility(from～8.6％to～4.0％).The austenite in aged steel presents more stability induced by the aging process than that in as-printed counterpart,which has a higher critical martensitic transformation stress of～1200 MPa than that of～780 MPa in as-printed steel.The austenite grains orientated with[200]//LD yield before the macro-yielding and preferential martensite transformation occurs.This study provides further insight into the intricated micromechanical responses of additively manufactured 18Ni300 maraging steel,enlarging the scope of its adaptation and application.
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