Control of intermetallic nano-particles through annealing in duplex low density steel

In high Al-low-density steels for future vehicle light weighting, it is vital to design a thermal profile to form and retain the uniformly dispersed nanosize B2-type intermetallic precipitates that are crucial for the material strength. In this paper, the influence of heating rate, during annealing to 1050°C was simulated in a Au-image furnace. The post annealing structure was then characterized and two different morphologies of B2 particles were observed: triangle-like with a few micrometres (≈1.4 μm) and disk-like precipitates with a diameter of around a few hundred nanometres. It was found that a slower heating rate (2.5°C/s) led to an increase in the volume fraction and to uniform distribution of particles within the microstructure and considerably affected the shape and size of the precipitates.