The microstructures of austenitic stainless steel welds typically contain a variety of complex austenite-ferrite structures. These structures are a result of both the solidification behaviour and subsequent solid state transformations which are controlled by both composition and weld cooling rates. The solidification cracking susceptibility is directly related, in a complex fashion, to the solidifying weld structure. The solidification and solid state transformations which occur during welding are reviewed in detail and this behaviour is related to solidification cracking susceptibility. Improved understanding of these phenomena offers an opportunity to improve commercial applications of austenitic stainless steels.

Microstructural development and solidification cracking susceptibility of austenitic stainless steel welds

The solidification behaviour of dilute aluminium–scandium alloys

Microstructures developed in commercial 17-4 PH precipitation-hardened stainless steel after different heat treatments have been studied. The martensite formed in this alloy has been found to be of a lath morphology having a dislocated substructure. Transmission electron microscopy studies have revealed the formation of a copper-rich phase in the samples aged at temperatures below 550°C. However, at higher temperatures, in addition to the formation of these precipitates, austenite phase reversion has been noticed, primarily at the lath boundaries. The reversion process has been found to be accompanied by a sharp decrease in the hardness of the alloy. The morphologies of the transformation products and the crystallography of the transformation have been discussed.

Effects of aging on the microstructure of 17-4 PH stainless steel

fractionation temperatures, and magmatic fractionation paths of Experiments in the Fe–Ni–Cu–S system were performed to identify these deposits. the role of the metal/S atomic ratio on monosulphide–melt partition coefficients and closed-system fractionation paths. In accord with previous work, DCu is >0·2 at all temperatures and all metal/S ratios. DNi is highly sensitive to temperature and metal/S, and

G. A. Chadwick

Papers

Metallography of phase transformations