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Microstructural attributes such as grain size d and dislocation density [[zeta].sub.d] affect the hysteretic magnetic properties of steels because they affect domain wall movement and pinning. In an earlier paper, a model was proposed for computing hysteresis loops based on the effect of grain size and dislocation density. In that paper, hysteresis loops were compared that all had the same maximum field [H.sub.max]. The result was that coercivity departed from linear relationships with inverse grain size (viz. 1/d) and [[zeta].sup.1/2.sub.d] for large values of 1/d and [[zeta].sup.1/2.sub.d].The same was true of hysteresis loss [W.sub.H], except that hysteresis loss even showed a peak, first increasing and then decreasing with increasing 1/d and [[zeta].sup.1/2.sub.d]. This kind of behavior had not been seen by experimenters, particularly core-loss people. It was learned that the core-loss experimenters compared hysteresis loops of the same maximum flux density [B.sub.max], instead of the same [H.sub.max]. In this paper, we use the model previously formulated to produce hysteresis loops with the same [B.sub.max]. Indeed, the appropriate linear relationships are found. The paper also addresses effects of uniaxial anisotropy on these microstructural magnetic effects and why two hysteresis parameters are affected by microstructural variation. Index Terms--Hysteresis modeling, magnetic materials, microstructural effects, uniaxial anisotropy effects.

This paper describes experiments with 2Cr-1Mo-grade steel at various stages of creep damage. Properties of magnetoacoustic emission (MAE) were tested and compared to other magnetic properties such as hysteresis loop B(H), Barkhausen effect (HBN), and magnetostriction [lambda]. The creep-damage stage was evaluated from microstructural analysis and mechanical properties tests. It was revealed that incipient creep damage leads to decrease of MAE and magnetostriction as well to slight decrease of coereivity Hc and to nonmonotonic behavior of HBN intensity. These features are discussed qualitatively using models of magnetic hysteresis and of MAE. Index Terms--Barkhausen effect, creep damage, magnetoacoustic emission, nondestructive evaluation.

Creep damage in steel causes a reduction of magnetic properties. A mathematical model, previously formulated, accounts for this. Recently, this model was used in finite element modeling (FEM) of a magnetic C-core signal due to creep damage at a seam weld in Cr-Mo steam pipe. The FEM assumed unrealistically that in the absence of creep damage, the weld material and heat-affected zone (HAZ) and base metal all had the same magnetic properties. In this paper, new finite element simulations are presented for worst case relative permeabilities of 1271, 784 and 571 for base metal, HAZ, and weld material. Reduced permeability at the weld results in a considerably reduced emf at low probe magnetic fields. However, creep damage does produce an additional emf reduction that is large enough to be detected, even when the creep damage does not extend to the pipe wall surface. A method is suggested for calibrating the magnetic signal for weld, HAZ, and base metal effects. Index terms - creep damage, magnetic NDE, seam weld, finite element modeling

This paper presents a way to relate two standard models for magnetomechanical hysteresis - the Sablik-Jiles-Atherton model and the Schneider-Cannell-Watts model - while at the same time presenting physical models for the asymmetry in magnetic property behavior under tensile and compressive stress in steel, including, for oH processes, the presence of an extremum in the dependence of magnetic properties on tensile stress, an effect which is sometimes known as the Villari effect.

[Co.sub.90][Fe.sub.10](2.5 nm)/Cu(2 nm, 3 nm, or 4 nm) multilayers (MLs) were DC magnetron-sputtered in the presence of a trace [N.sub.2] sputtering gas constituent during CoFe layer growth. A reduction in saturation magnetization and easy axis coercivity coupled with an increase in resistivity was observed for the nitrided MLs compared to metallic MLs with identical Cu layer thickness.

Using appropriately modified magnetization curves for each element of creep-damaged material, a finite element calculation has been carried out to simulate magnetic detection of non.uniform creep damage around a seam weld in a 2.25 Cr 1 Mo steam pipe. The magnetization curves for the creep-damaged elements were obtained from an earlier model for the magnetic effect of a uniformly creep-damaged material as given by Chen, et al. In the finite element calculation, a magnetic C-core with primary and secondary coils was placed with its pole pieces flush against the specimen in the vicinity of the weld. The secondary emf was shown to be reduced when creep damage was present inside the pipe wall at the cusp of weld and In the vicinity of the cusp. The C-core detected the creep damage best if it completely spanned the weld seam width. Also, the current in the primary needed to be such that the C-core was not magnetically saturated.