Cosegregation of metal and nonmetal atoms in FeCrAl alloys under ultrafast cooling state

In iron-based alloys, a series of micro-segregation is caused by localised slow cooling due to large-size configurations, and the regulation of solute-atom grain-boundary segregation has far-reaching effects on the structural properties of polycrystalline materials. Here, researchers report that ultrafast cooling techniques are utilised in conventional casting processes to provide control of grain boundary elemental segregation. In alloys with low oxygen and nitrogen, the interaction force between trace nonmetallic impurity atoms and metal alloy atoms greatly alters the state of grain boundary segregation. Two special atomic cosegregation processes for Al–N and Cr–O–C exist simultaneously in the slow-cooled state. However, the ultrafast cooling states (V_c= 1602.6 °C/s) will effectively inhibit the Cr–O–C atomic cosegregation and precipitate nano-AlN precipitation phases at grain boundaries and stabilise the grain boundary structure. We further demonstrate this property remains similarly regular in high-oxygen concentration specimens. Our related research not only expands new insights into the cosegregation of metallic and nonmetallic atoms in conventional casting processes under ultrafast cooling states, but also provides new ideas for solving the problem of corrosion resistance, strength and other performance degradation due to Cr atomic segregation.