Thermal stability of Pd-Au core-shell nanostructures in an in-situ liquid TEM

Abstract

Abstract This research investigates the tensile properties of two ferritic stainless steels, 022Cr18Ti and 022Cr18NbTi, under elevated temperatures. Special emphasis was placed on the influence of titanium (Ti) and niobium (Nb) on the high-temperature tensile strength of the steels. Employing metallurgical microscopy (OM) and scanning electron microscopy (SEM), an in-depth analysis of the fracture morphology and microstructure of the specimens was conducted. High-temperature tensile tests were performed at a strain rate of 0.001s-1 over a temperature range of 300 °C to 900 °C. The results demonstrate that the high-temperature strengths of both stainless steels significantly decrease with increasing temperatures. However, 022Cr18NbTi, containing dual Nb-Ti stabilizing elements, exhibits superior high-temperature performance, notably at 700 °C, where its strength surpasses that of 022Cr18Ti by 91 MPa. The microstructure reveals that the addition of Nb promotes the precipitation of a higher density of fine, dispersed secondary phases at elevated temperatures. This process refines the grain structure and contributes to precipitation strengthening, significantly enhancing the material’s high-temperature strength. However, as the temperature rises, Coarsening of precipitates reduces the strengthening effect.