Sensitivity of Conventional and Non-destructive Characterization Techniques to Recovery and Recrystallization

Abstract

The sensitivity and limitations of magnetic coercive field, hardness, metallographic measurements and electron back scattered diffraction analysis are studied and discussed in terms of monitoring recovery and the onset and evolution of recrystallization in a cold rolled low carbon steel. The magnetic coercive field shows much higher resolution than hardness measurements when measuring recovery. Hardness is almost insensitive to the microstructural changes taking place in the material during annealing treatments performed at low temperatures. The conditions under which the magnetic coercive field measurements can also be used to monitor recrystallized fraction are also discussed.

Sensitiveness of Magnetic Inductive Parameters for the Characterization of Recovery and Recrystallization in Cold-Rolled Low-Carbon Steel

“…According to the results of the microstructural characterization shown in Figures 6 and 7 and described in more detail elsewhere, [21] clear microstructural indications of incipient recrystallization are observed after the annealing treatment for 10,000 seconds at 773 K (500°C). Recrystallization is evident at 848 K (575°C) for annealing times longer than about 100 seconds.…”

“…[21] Figure 6 shows the evolution of the recrystallized fraction at 848 K (575°C) as a function of the annealing time. The EBSD images in Figure 7 illustrate the evolution of the microstructure as a function of annealing conditions.…”

“…The obtained specimens were isothermally annealed at laboratory at low temperatures, 573, 673, and 773 K (300, 400, and 500°C), in order to promote recovery and avoid interaction with recrystallization, and at a higher temperature, 848 K (575°C), in order to produce samples with various degrees of recrystallization. [21] The samples were heated in an argon atmosphere, at a rate of 20 K/s (20°C/s), to the holding temperatures kept at this temperature for annealing times in the range of 1 to 10,000 seconds and quenched in helium to room temperature at a rate close to À60 K/s (60°C/s).…”

“…[17] Earlier studies on cold-rolled low carbon steels showed that some parameters derived from magnetic hysteresis loops can be useful to characterize recovery and to detect the onset of recrystallization. [18][19][20][21][22][23] Additionally, it was found that the coercive field could also be employed to characterize the progress of recrystallization when the variation of the effective size of microstructure during recrystallization was very small. [21,22] Following that study, this article researches into the use of other magnetic inductive parameters derived from magnetic hysteresis loop measurements for the nondestructive characterization of recovery and recrystallization during the annealing of a cold-rolled steel.…”

“…[18][19][20][21][22][23] Additionally, it was found that the coercive field could also be employed to characterize the progress of recrystallization when the variation of the effective size of microstructure during recrystallization was very small. [21,22] Following that study, this article researches into the use of other magnetic inductive parameters derived from magnetic hysteresis loop measurements for the nondestructive characterization of recovery and recrystallization during the annealing of a cold-rolled steel. In particular, this article focuses on the analysis of the effect of the textural changes occurring during recrystallization on the magnetic response, in order to distinguish between contributions from crystal orientation and from microstructure.…”