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A novel selective-area texturing process using a pulsed laser to produce a new form of texture in only the landing zone is discussed. By rotating the media under the focused pulsed-laser beam, a row of crater shaped dimples are created in the landing zone only. The rest of the disk remains smooth and untextured. Contact start-stop (CSS) test results from a lubricated C/CoCrTa/Cr media on the laser-textured substrate exhibited a constant static friction coefficient of 0.17 even after 12-K CSS cycles, with no apparent friction buildup. This unique behavior is attributed to the rounded and smooth surface topography of the laser-textured media.

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The Navier-Stokes equation and the species continuity equation have been solved numerically in a boundary fitted coordinate system comprising the geometry of a single strand bare tundish. The solution of the species continuity equation predicts the time evolution of the concentration of a tracer at the outlet of the tundish. The numerical prediction of the tracer concentration has been made with nine different turbulence models and has been compared with the experimental observation for the tundish. It has been found that the prediction from the standard k-1 model, the k-1 Chen-Kim (ck) and the standard k-1 with Yap correction (k-1 Yap), matches well with that of the experiment compared to the other turbulence models as far as gross quantities like the mean residence time and the ratio of mixed to dead volume are concerned. It has been found that the initial transient development of the tracer concentration is best predicted by the low Reynolds number Lam-Bremhorst model (LB model) and then by the k-1 RNG model, while these two models under predict the mean residence time as well as the ratio of mixed to dead volume. The Chen-Kim low Reynolds number (CK low Re) model (with and without Yap correction) as well as the constant effective viscosity model over predict the mixing parameters, i.e. the mean residence time and the ratio of mixed to dead volume. Taking the solution of the k-1 model as a starting guess for the large eddy simulation (LES), a solution for the LES could be arrived after adopting a local refinement of the cells twice so that the near wall y + could be set lower than 1. Such a refined grid gave a time-independent solution for the LES which was used to solve the species continuity equation. The LES solution slightly over predicted the mean residence time but could predict fairly well the mixed volume. However, the LES could not predict both the peaks in the tracer concentration like the k-1, RNG and the Lam-Bremhorst model. An analysis of the tracer concentration on the bottom plane of the tundish could help to understand the presence of plug and mixed flow in it.

Stacking faults ͑SFs͒ and fcc-phased grains are studied by electron diffraction in perpendicular media. Co-alloy compositions, such as CoCrPt, CoCrPtB, are compared on different underlayers and deposition conditions. It is found that CoCrPtB alloys tend to have greater amount of SFs and fcc grains than the CoCrPt alloy. Underlayers as well as low deposition rate and base pressure help to reduce the amount of SFs and fcc phase.

Results on annealed nickel show that the total number of counts of both magnetic and acoustic Barkhausen signals vary inversely with grain size. In decarburized steels the total number of counts and the amplitude of both Barkhausen signals increase in proportion to grain size. The paper addresses these results in context of grain size, grain-boundary segregation, and precipitate effect. Results on annealed nickel show that the total number of counts of both magnetic and acoustic Barkhausen signals vary inversely with grain size. In decarburized steels the total number of counts and the amplitude of both Barkhausen signals increase in proportion to grain size. The paper addresses these results in context of grain size, grain~boundary segregation, and precipitate effect.

Dislocations affect the magnetic properties of ferromagnetic materials by pinning the domain walls. The primary mechanism is interaction between the stress fields of dislocation and domain walls. Using magnetic nondestructive methods, namely the acoustic Barkhausen noise (AB), magnetic Barkhausen noise (MB), and the hysteresis curves, we have studied these interactions. The three measurements give different types of information. AB provides information about non-180° type domain wall interaction, MB primarily provides information about 180° domain wall interaction, and the hysteresis curve about both these interactions as well as about rotation of domain walls. The paper presents results obtained on polycrystalline nickel which was first deformed and then annealed at different temperatures in order to achieve different dislocation densities. The results show that AB and hysteresis loss follow the same trend as hardness. MB results, however, change in a more complex fashion which is sensitive to grain recrystallization as well as dislocation structure. Interesting features of these results will be discussed in detail. Dislocations affect the magnetic properties of ferromagnetic materials by pinning the domain walls. The primary mechanism is interaction between the stress fields of dislocation and domain walls. Using magnetic nondestructive methods, namely the acoustic Barkhausen noise (AB), magnetic Barkhausen noise (MB), and the hysteresis curves, we have studied these interactions. The three measurements give different types of information. AB provides information about non-180· type domain wall interaction, MB primarily provides information about 180· domain wall interaction, and the hysteresis curve about both these interactions as well as about rotation of domain walls. The paper presents results obtained on polycrystalline nickel which was first deformed and then annealed at different temperatures in order to achieve different dislocation densitieso The results show that AB and hysteresis loss follow the same trend as hardness. MB results, however, change in a more complex fashion which is sensitive to grain recrystallization as well as dislocation structure. Interesting features of these results will be discussed in detail. INTRODUCTION EXPERIMENTAL DETAILS AND RESULTS