Picture of the month - June 2026

This is the surface of a duplex stainless steel. The polished surface was accidentally oxidised during heat treatment. In the image, two types of structure can be observed: ferrite grains, predominantly equiaxed in shape, and austenite, typically found at the ferrite grain boundaries but also in the form of Widmanstätten patterns. The original ferrite grains formed during solidification can also be seen in black.

The image was taken at the Department of Materials Science and Engineering at McMaster University in Hamilton, Canada, during a collaboration between McMaster and the SIMaP laboratory. The image was produced as part of the PhD thesis by João Leonardo da Silva Trosdtorf, entitled: "Genesis of microstructures in the heat-affected zones of lean duplex stainless steel welds."

The author would also like to thank Dr Zurob of McMaster University, SIMaP and the IDEX grant for making the visit possible, which enabled this image to be produced.