Enhancing Material Performance Through Grain Boundary Network Engineering

One of the major challenges in materials science for decades has been to increase toughness without degrading strength. Many material innovations address this impasse for specific materials; toughened glass, reinforced concrete, grain refined steels are a few examples. Yet the problem remains for the majority of engineering materials. We recently found a way to achieve this in high strength steels. The breakthrough hinges on the role played by the grain boundary network. Significant gains in toughness were achieved with little impact on strength when the grain boundary network was altered. The present proposal will exploit a new characterisation technique developed by my group to determine the extent to which steel processing can be employed to optimize the grain boundary network.

The study will focus on improving the toughness of hydrogen embrittled ultrahigh strength steels, but the fundamental knowledge generated will have potential to be more widely applied to other metallic materials. The aim is to explore the impact of processing routes on the microstructure characteristics of steel, in particular its three-dimensional grain boundary network, using state of the art multi-scale characterization techniques in conjunction with advanced computational tools to determine:

1. the impact of solid-solid phase transformation mechanisms on the nature of grain boundary character
2. the topology of grain boundary planes in polycrystalline materials
3. the role of grain boundary network on hydrogen segregation and embrittlement in ultrahigh strength steels.

The research will determine the role of processing paths on microstructure network characteristics using advanced multi-scale characterization techniques. This will ultimately lead to the development of new alloys and microstructures with novel property combinations, particularly increased toughness in high strength grades (i.e., enhancing performance and extending material life). Hence, this research will be anticipated to offer wide industrial applications leading to significant cost savings and benefits. The approach will be used for steel as a model alloy and will have the potential to be employed for other alloying systems. This knowledge also makes it possible to unveil the mechanism of microstructure formation in the additive manufactured metals, where the material undergoes complex processing routes. This ultimately enables exploration of material performance improvement through engineering the grain boundary network characteristics.