4 research outputs found
Analysis of ferrite formed in 321 grade austenitic stainless steel
A significant fraction of ferrite has been identified in a 321 grade austenitic stainless steel in the
solution heat treated condition. The microstructures were analysed using electron backscatter
diffraction, energy dispersive X-ray spectroscopy and X-ray diffraction (XRD) and the stability of
the ferrite investigated using heat treatments in a tube furnace, dilatometry and high temperature
XRD. The ferrite dissolved ,800uC, then formed again on cooling at temperatures under 200uC.
Thermodynamic predictions showed a significant ferrite content at room temperature under
equilibrium conditions, and the DeLong diagrams predict an austenitezmartensite microstructure
in the cast condition. Sensitivity analysis on the DeLong diagram has shown that the nitrogen
content had a large effect on the austenite stability. The instability of the austenite and the
subsequent transformation to ferrite on cooling can be attributed to low nitrogen content
measured in the as received material. It was found that thermal aging of the material caused
further transformation of austenite to ferrite as well as the formation of sigma phase that appears
higher in nitrogen than the matrix phases. The diffusion of nitrogen into sigma phase may cause
instability of the austenite, which could cause further transformation of austenite to ferrite on
cooling from the aging temperature. The transformation of austenite to ferrite is known to be
accompanied by an increase in volume, which may be of relevance to components made with
tight dimensional tolerances
S1: Physicochemical hazard assessment of ash and dome rock from the 2021 eruption of La Soufrière, St Vincent, for the assessment of respiratory impacts and water contamination
Further information on particle size analysis methods and information provided in IVHHN report of leachate data, on volcanic ash impacts on animal healt