An EBSD study of the deformation of service-aged 316 austenitic steel

Electron backscatter diffraction (EBSD) has been used to examine the plastic deformation of an ex-service 316 austenitic stainless steel at 297K and 823K (24 °C and 550 °C)at strain rates 3.5x10-3 to 4 x 10-7 s-1. The distribution of local misorientations was found to depend on the imposed plastic strain following a lognormal distribution at true strains 0.1. At 823 K (550 °C), the distribution of misorientations depended on the applied strain rate. The evolution of lattice misorientations with increasing plastic strain up to 0.23 was quantified using the metrics kernel average misorientation, average intragrain misorientation, and low angle misorientation fraction. For strain rate down to 10-5 s-1 all metrics were insensitive to deformation temperature, mode (tension vs. compression) and orientation of the measurement plane. The strain sensitivity of the different metrics was found to depend on the misorientation ranges considered in their calculation. A simple new metric, proportion of undeformed grains, is proposed for assessing strain in both aged and unaged material. Lattice misorientations build up with strain faster in aged steel than in un-aged material and most of the metrics were sensitive to the effects of thermal aging. Ignoring aging effects leads to significant overestimation of the strains around welds. The EBSD results were compared with nanohardness measurements and good agreement established between the two techniques of assessing plastic strain in aged 316 steel

Characterization of (1-x)[Bi12In0.5O18.75 + *g-Bi2O3]:(x)PbTiO3 ceramics

The ceramic system with composition (1-x)[Bi12In0.5O18.75 + *g-Bi2O3]:(x)PbTiO3 with x = 0.0, 0.3, 0.5 and 0.8 was synthesized and subsequently characterized for its crystal structure and dielectric properties. X-ray diffraction showed that the ceramic with nominal composition Bi12In0.5O18.75 + *g-Bi2O3 has sillenite structure, which is an uncommon metastable mineral phase with composition Bi12In0.5O18.75. The dielectric constants and loss tangents were measured at different frequencies and temperatures. The dielectric properties of the sample with x = 0.0, Bi12In0.5O18.75+*g-Bi2O3, showed strong frequency and temperature dependence of dielectric constant and loss tangent. The high value of both the dielectric constant and loss tangent showed a conductivity value similar to a typical semiconductor. The addition of PbTiO3 significantly reduced the temperature and frequency dependence at the low frequency range. For the sample x = 0.8 (80% PbTiO3) the dielectric properties are similar to a typical dielectric material and the conductivity was not revealed in the loss tangent. The results indicate that the electrical properties of (1-x)[Bi12In0.5O18.75 + *g-Bi2O3]:(x)PbTiO3 ceramics can be tuned from a conducting oxide to an insulator and to dielectric, depending on the amount of PbTiO3