X-ray diffraction (XRD) and Mossbauer spectroscopy (MS) measurements were used to evaluate the content of alpha' ferromagnetic phase in AISI 304 steel cold rolled and then heat treated for increasing times (up to 7.2 x 10(4) s) at 673 K. Both analytical techniques show the same trend of alpha' content versus annealing time, characterized by two maxima. The first maximum has been attributed to the growth of preexisting martensitic zones due a different microstress relaxation in the two phases, which induces a stress gradient through the alpha'/gamma interface forcing it to move. The second maximum was explained assuming that local composition variations were induced by carbide precipitation and that a new martensitic phase may form during cooling to room temperature. MS data, i.e. the increase of average hyperfine field of magnetic fraction and the constancy of austenite isomer shift, and the analysis of precision XRD peak profiles support this assumption. Furthermore, MS measurements evidenced in cold rolled samples the presence of layers with decreasing martensite content towards the inside. (C) 1999 Elsevier Science S.A. All rights reserved.
Gauzzi, F., Montanari, R., Principi, G., Perin, A., Tata, M.e. (1999). Martensite formation during heat treatments of AISI 304 steel with biphasic structure. In Materials Science and Engineering A (pp.443-447). LAUSANNE : ELSEVIER SCIENCE SA.
Martensite formation during heat treatments of AISI 304 steel with biphasic structure
GAUZZI, FRANCO;MONTANARI, ROBERTO;TATA, MARIA ELISA
1999-01-01
Abstract
X-ray diffraction (XRD) and Mossbauer spectroscopy (MS) measurements were used to evaluate the content of alpha' ferromagnetic phase in AISI 304 steel cold rolled and then heat treated for increasing times (up to 7.2 x 10(4) s) at 673 K. Both analytical techniques show the same trend of alpha' content versus annealing time, characterized by two maxima. The first maximum has been attributed to the growth of preexisting martensitic zones due a different microstress relaxation in the two phases, which induces a stress gradient through the alpha'/gamma interface forcing it to move. The second maximum was explained assuming that local composition variations were induced by carbide precipitation and that a new martensitic phase may form during cooling to room temperature. MS data, i.e. the increase of average hyperfine field of magnetic fraction and the constancy of austenite isomer shift, and the analysis of precision XRD peak profiles support this assumption. Furthermore, MS measurements evidenced in cold rolled samples the presence of layers with decreasing martensite content towards the inside. (C) 1999 Elsevier Science S.A. All rights reserved.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
