<i>In situ</i> Neutron Diffraction Study on Ferrite and Pearlite Transformations for a 1.5Mn-1.5Si-0.2C Steel

Abstract

The phase transformation behavior from austenite upon cooling in a 1.5Mn-1.5Si-0.2C steel was in situ monitored using dilatometry, X-ray and neutron diffractions. The starting temperature of ferrite transformation was in good agreement between dilatometry and neutron diffraction, whereas much higher in X-ray diffraction. Such a discrepancy in transformation temperature is attributed to the change in chemical composition near the surface of a specimen heated to elevated temperatures in a helium gas atmosphere for X-ray diffraction. In situ neutron diffraction enables us to investigate the changes in lattice constants of ferrite and austenite, which are affected by not only thermal contraction but also transformation strains, thermal misfit strains and carbon enrichment in austenite. Pearlite transformation started after carbon enrichment in austenite reached approximately 0.7 mass% and contributed to diffraction line broadening.

Synthesis of Hard Layer by Titanium Addition During Welding Process and Quenched Directly

“…The plane peaks (110) and (211) are reflections of the α-iron (ferrite) phase. These α-iron phase plane peaks are in good agreement with the results of other studies [26][27][28]. The peak magnification of 110 plane diffraction patterns in the inset of Figure 3 (2θ = 50-53°) shows an asymmetric peak shape.…”

Optimization of Aging Temperature and Heat-Treatment Pathways in Additively Manufactured 17-4PH Stainless Steel

“…Although sample SS revealed a higher YS of 539 MPa than that of sample AB without a plateau, it exhibited degraded performance, showing a TE of 1113 MPa at a UE of 5.78%, and fracture at 15.7%. This indicated that sample AB with a large amount of retained austenite had an advantage in The interstitial atom concentration and residual stress are key factors in determining the lattice parameters [21][22][23][24]. Since interstitial atoms are less soluble in BCT martensite, the decrease in the BCT lattice parameter was caused by the diffusion of interstitial atoms with heterogeneous distributions into austenite with a higher solubility [2,17,25], as well as the attenuation of martensite defects (a tempering effect) [26], both of which occurred during the aging process.…”

“…The phase fraction of austenite grew to 60.8% at the aging temperature of 400 • C, and this increasing tendency persisted up to the aging temperature of 490 • C (62.6%). The sample aged at 520 • C showed a relatively low fraction of retainued austenite (57%) and at increasing temperatures of aging treatment, the fraction of retained austenite continued to decline, reaching 15.9% at the aging temperature of 700 • C. The interstitial atom concentration and residual stress are key factors in determining the lattice parameters [21][22][23][24]. Since interstitial atoms are less soluble in BCT martensite, the decrease in the BCT lattice parameter was caused by the diffusion of interstitial atoms with heterogeneous distributions into austenite with a higher solubility [2,17,25], as well as the attenuation of martensite defects (a tempering effect) [26], both of which occurred during the aging process.…”