Dynamic Young’s moduli of tungsten and tantalum at high temperature and stress

Recently reported results of the long lifetime of the tungsten samples under high temperature and high stress conditions expected in the Neutrino Factory target have strengthened the case for a solid target option for the Neutrino Factory. In order to study in more detail the behaviour of the material properties of tungsten, a dynamic method has been used for measurement of Young's modulus at high stress, high-strain-rates (>1000 s(-1)) and very high temperatures (up to 2650 degrees C). The method is based on measurements of the surface vibration of thin wires, stressed by a pulsed current, using a Laser Doppler Vibrometer. The measured characteristic frequencies under the thermal excitation have been used to obtain Young's modulus as a function of applied stress and temperature. The same procedure has been used to measure Young's modulus of tantalum up to 2500 degrees C. (C) 2010 Elsevier B.V. All rights reserved

Microstructural evolution of submicron sized ferrite in bimodal structural ultrafine grained ferrite/cementite steels by annealing below austenized temperature

The microstructural evolution of submicron sized ferrite in bimodal structural ultrafine grained ferrite/cementite steels with 0.15 pct carbon content and 0.45 pct carbon content upon annealing below the austenized temperature was investigated. The average grain sizes of the ferrites with a normal density and with a high density of cementite particles were plotted, respectively, as a function of the annealed temperature and time, and exhibited different coarsening behaviors. The average grain sizes of the ferrites with a normal density of cementite particles gradually coarsened by increasing the annealing temperature or time, while those with a high density of cementite particles hardly changed at first, and then coarsened after reaching a certain annealing condition. The coarsening of the ferrite grain size in the steel with 0.15 pet carbon content occurred much more readily than that in the steel with 0.45 pet carbon content upon annealing. The spacing and the critical spacing of cementite particle were measured and hypothetically calculated, respectively. The size and the distribution of cementite particles was one of the critical factors affecting the microstructural evolution in this type of cementite particle spherodized steels. Most of the coarsening of the ferrite grain size occurred after the cementite particle spacing reached the required critical value