Improvement of the Mechanical Properties of Al-Alloyed High Strength Steels by Intermetallic Precipitation Strengthening

  Crystal structures of the intermetallic (Ni/Fe)Al- (B2) and κ- (L´12) phases. IEHK Crystal structures of the intermetallic (Ni/Fe)Al- (B2) and κ- (L´12) phases.

Intermetallics possess outstanding physical and mechanical properties, such as a high thermal stability, resistance to oxidation and a high specific strength. The lack of intermetallics in structural applications is related to their poor room temperature ductility. Precipitation strengthening of conventional alloys for structural applications by intermetallic phases is becoming increasingly popular.

In the project, new concepts for intermetallic strengthening based on the B2- [(Fe,Ni)Al], DO3-[Fe3Al] and the κ-phase [(Fe,Mn)3AlC] are developed by adjustments in alloy composition, microstructure design and processing conditions. Simplified alloy compositions are developed to investigate the precipitation kinetics by synchrotron X-ray experiments. Information gained on the nucleation of intermetallic precipitates is input into phase field simulations in order to simulate the precipitation kinetics and microstructure evolution. A validation of the simulated microstructure and precipitation kinetics is performed by scanning/transmission electron microscopy and in-situ synchrotron experiments at specific annealing temperatures, respectively. The influencing variables of intermetallic precipitates on the mechanical properties will be obtained and the gained insights applied to more complex, Al-alloyed high strength steels.