By identifying the relationship between the time required to obtain bainite and parameters such as the transformation temperature and carbon concentration, it has been possible to institute a design procedure that led to the desired mechanical properties and transformation characteristics. The work has also identified difficulties in the calculation of tensile elongation on the basis of a percolation model, which suggests that fracture occurs when the fraction of austenite drops below the percolation threshold in the microstructure.

No abstract

Well-designed cementite-free bainitic steels are important in contributing to unique combinations of strength, toughness and cost. We examine here the relative effects of molybdenum and boron on the kinetics of transformation of austenite particularly into allotriomorphic ferrite and bainite. There are some surprising results on the role of boron, which is found in some circumstances to accelerate the transformation to allotriomorphic ferrite. This, and other features of transformation behaviour are assessed in the context of phase transformation mechanisms.

We report the observation of radio frequency-superconducting quantum interference device (rf-SQUID) effect due to natural grain boundary weak links in a bulk sample of a YNi2B2C superconductor at 4.2 K, confirming that the superconducting grains are coupled at the grain boundaries through Josephson effect. Periodic oscillations in voltage-flux characteristic due to rf-SQUID effect have been clearly observed at 4.2 K when the driving rf frequency was kept slightly away from the resonance frequency of the tank circuit. Phase reversal in the voltage-flux characteristics on changing the rf frequency has been observed. Noise spectrum of the YNi2B2C bulk rf-SQUID is also reported.

The harmonic generation effect in superconducting Bi(Pb) - Sr - Ca - Cu - O screen printed thick film is reported. When an ac field of frequency 10 kHz is applied to the film, odd harmonics corresponding to frequencies 30, 50 and 70 kHz are observed. The addition of a dc field , induces the generation of even harmonics at frequencies 20, 40, 60, 80 kHz. The amplitudes of these harmonics are studied as a function of and . In the low-field region the amplitude of the even harmonics has been found to vary linearly with with the maximum amplitude change found for the second harmonic. The development of a high- thick film magnetometer based on the measurement of the amplitude of the second harmonic is described. The sensitivity of this magnetometer has been found to depend on and on the frequency of the ac field. The lowest field noise was found to be T.