TY - JOUR
T1 - Laser-pulse heat treatment
T2 - Application to reaustenitisation from ferrite/cementite mixtures
AU - Reed, R. C.
AU - Shen, Z.
AU - Akbay, T.
AU - Robinson, J. M.
N1 - Funding Information:
One of the authors (ZS) would like to thank the Chinese Government and the British Council for finan- cial support. Two of the authors (TA and RCR) are grateful to the EPSRC for financial support under grant reference GR/J 36938 “Theory for the Reausteni-tisation Kinetics in Low-Alloy Steels” and to Professor M. McLean for the provision of laboratory facilities at Imperial College. The authors are grateful to Dr Man-abu Takahashi of Nippon Steel Corporation for supplying the steel ingot which was used for this work.
PY - 1997/7/31
Y1 - 1997/7/31
N2 - A technique capable of monitoring microstructural changes under conditions of rapid heating and cooling is presented. It involves the application of a high-powered 1 kW CO2 laser beam to thin-foil specimens. The thermal cycle at the reverse face of the specimens is recorded during irradiation using thermocouples and a purpose-built data acquisition system. The method has been used to study the formation of austenite from a mixture of ferrite and cementite in a high purity Fe-0.4C (wt%) steel, in the heavily spheroidised condition. For foils of 3 mm diameter, it is found that the heating rates observed are between 104 and 105°C/s for laser beam radii between 2.9 and 0.9 mm. Pulse lengths necessary to reach austenitisation temperatures are then between 100 and 10 ms. These numerical results are consistent with the predictions of a very simple numerical model which assumes one-dimensional heat conduction. Consistent with the literature, it is found that nucleation of austenite occurs preferentially at ferrite/cementite interfaces; however, the incubation period appears to be undetectable, even on the timescale of the present experiment.
AB - A technique capable of monitoring microstructural changes under conditions of rapid heating and cooling is presented. It involves the application of a high-powered 1 kW CO2 laser beam to thin-foil specimens. The thermal cycle at the reverse face of the specimens is recorded during irradiation using thermocouples and a purpose-built data acquisition system. The method has been used to study the formation of austenite from a mixture of ferrite and cementite in a high purity Fe-0.4C (wt%) steel, in the heavily spheroidised condition. For foils of 3 mm diameter, it is found that the heating rates observed are between 104 and 105°C/s for laser beam radii between 2.9 and 0.9 mm. Pulse lengths necessary to reach austenitisation temperatures are then between 100 and 10 ms. These numerical results are consistent with the predictions of a very simple numerical model which assumes one-dimensional heat conduction. Consistent with the literature, it is found that nucleation of austenite occurs preferentially at ferrite/cementite interfaces; however, the incubation period appears to be undetectable, even on the timescale of the present experiment.
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U2 - 10.1016/s0921-5093(97)00113-5
DO - 10.1016/s0921-5093(97)00113-5
M3 - Article
AN - SCOPUS:0012832716
SN - 0921-5093
VL - 232
SP - 140
EP - 149
JO - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
JF - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing
IS - 1-2
ER -