Effect of ageing temperature on reverse austenite content in AISI 630 stainless steel

• Published in: Materialwissenschaft und Werkstofftechnik Vol. 50; no. 4; pp. 405 - 411
• Main Authors: Burja, J., Šuler, B., Nagode, A.
• Format: Journal Article
• Language: English
• Published: 01-04-2019
• Subjects: Ausscheidungshärtender Stahl; copper precipitates; Kupfer-Ausscheidungen; phase transformations; Phasenumwandlung; Precipitation hardening steel; Restaustenit; reverse austenite; rostfreier Stahl; stainless steel
• ISSN: 0933-5137; 1521-4052
• DOI: 10.1002/mawe.201800045

The alloy AISI 630 (ASTM A564‐89 17‐4 PH) is a precipitation hardening stainless steel with good mechanical and corrosion properties. Mechanical properties strongly depend on the microstructure. Namely, the formation of the reversed austenite and coarsening of copper rich precipitates cause a substantial drop of hardness. Thus, the evolution of the microstructure during ageing was thoroughly investigated in order to explain the processes that have effect on formation of the reversed autenite. The reaustenitization was analyzed with a dilatometer, while the coarsening of copper rich precipitates was observed by transmission electron microscope. The amount of austenite was measured with x‐ray diffraction and the impact of austenite on the fracture appearance transition temperature was observed. It was found that the amount of the so called reverse austenite does not only depend on the amount of transformed austenite but also on its chemistry, as it dictates its ability to transform into martensite during cooling.