The purpose is to design and characterise novel aeroengine shaft alloys with better combinations of low and high temperature properties. The shafts have specific requirements of strength, ductility, fatigue- and creep-resistance, high purity and thermal stability. One approach involves the re-examination of secondary hardening alloy systems, where carbides are used to achieve strength and creep resistance. The characterisation of a commercially available alloy has revealed poor creep ductility and unacceptable thermal stability. The intention is to redesign the alloy and validate it experimentally. Based on previous work, reduced austenite grain size contributes to the creep properties, therefore the second approach is to microalloying F1E by adding small concentrations of niobium and carbon, to control the austenite grain size. It is found that the niobium and carbon are effective in refining the austenite grain size, but their role on a range of other properties needs to be thoroughly assessed.