Papers by Author: X. Zhao

Abstract: A 12-Tesla magnetic field was applied during the transformation from austenite to ferrite and then pearlite in a medium plain carbon steel at two different cooling rates. Results show that when cooling is slow, the magnetic field shows an effect of promoting proeutectoid ferrite grains to grow along the field direction that results in an elongated grain microstructure. However, when cooling is fast, the magnetic field mainly shows an effect of reducing the amount of low angle misorientations and increasing the amount of CSL boundaries. In addition, the magnetic field exhibits a slight enhancement of the <001> texture component in the direction that is perpendicular to the field direction (TFD).

Abstract: High magnetic fields were applied to the austenite to proeutectoid transformation and tempering process in a 42CrMo steel. The thermodynamic and kinetic effects of the high magnetic field on the austenite decomposition show that it can obviously increase the amount of the product ferrite and accelerate the transformation by enhancing the Gibbs free energy difference between the parent and product phases. Moreover, the magnetic field can considerably lower the amount of low angle misorientations of ferrite in pearlite colonies and obviously increase the frequency of S3-29 coincidence boundaries, especially S3 boundaries, of the ferrite. But it has no obvious effect on crystallographic orientation distribution. When the field is applied to the high temperature tempering process, it can effectively prevent the directional growth of cementite along martensite plate boundaries and twin boundaries by increasing both the cementite/ferrite interfacial energy and the magnetostrictive strain energy. Finally, particle-like cementite is obtained. The magnetic field also obviously retards the formation and growth of the ‘distortion-free’ regions of the matrix.

Abstract: Fe-3.10%Si thin strips were prepared by symmetric and asymmetric cold rolling from commercial grain oriented silicon steel sheets, then annealed with and without a magnetic field. Magnetic field of 12T was applied along the rolling direction. Magnetic annealing does not essentially change the texture development that recrystallization texture consists mainly of η fiber (RD//<001>), and the strongest component tends to transform from Goss ({110}<001>) to {210}<001> with the increase in speed ratio and annealing temperature. But magnetic annealing promotes Goss component in the strips rolled with small speed ratios, while decreases {210 <001> component in those rolled with large speed ratios. Possible effect mechanism of magnetic annealing was discussed.

Abstract: High magnetic field is applied with the field direction parallel to the rolling direction during annealing of a cold rolled IF steel sheet. Results of X-ray ODF analysis show that, magnetic field annealing retards the normal recrystallization texture evolution for the IF steel sheet. It is worth noting that an abnormal increase of orientation intensity at {100}<110> is found after magnetic annealing for 25min at 650°C. When the magnetic field strength is increased from 10 Tesla to 14 Tesla, the a-fiber is further strengthened, especially the {100}<110> component. Combined with EBSD analysis results, it is considered that the magnetic field does not change the mechanism of recrystallization texture evolution for the IF steel sheet in the present case.

Abstract: The Weiss model is extended by substituting the molecular field coefficient lwith a short-range-ordering coefficient g valid around and above Tc. The temperature variations of susceptibility of fcc Fe are calculated with a band model. Based on the above models, the phase equilibrium diagram of Fe-C binary system under a magnetic field is calculated.

Abstract: The cold-rolled 3104 aluminum alloy sheets were annealed without and with an electric field. Results show that the electric field can greatly postpone the recovery and recrystallization processes, enhance the Cube texture component. The effect of the electric field lies in that it decreases the concentration of the electronegative vacancies by attracting them to the electropositive sample surface, thus reducing the stored energy for recovery and recrystallization.