Dislocation relaxation and alloy softening of bcc alloys

Recently, low-frequency internal friction measurements on a series of Fe–Cr alloys by Konstantinovi? and Terentyev [M.J. Konstantinovi? and D. Terentyev, Mater. Sci. Eng. A 521–522 (2009) p.106] have demonstrated that increasing Cr concentrations lead to an increase in the strength of the β-relaxation at the cost of the γ-relaxation (Chambers’ notation). In the same concentration and temperature regime, the alloys show alloy softening. It is argued that both phenomena are due to the same process, namely the influence of foreign atoms on the transformation of the cores of a ₀?1 1 1?/2 screw dislocations from their low-temperature configuration, capable of forming kink pairs on {1 1 0} planes, to their high-temperature configuration with kink-pair generation on {2 1 1} planes.     

Electrodeposition,assisted by abrasive polishing,of crack-free hard chromium with compressive stress

Crack networks and residual tensile stresses are general characteristics of electrodeposited hard chromium coatings. In this paper, crack-free hard chromium coatings with compressive stresses have been obtained by an electrodeposition process assisted by abrasive polishing. The deposited coatings had mirror-like smooth surfaces, values of hardness in the range 800–1000 HV and compressive stresses between 1000 and 1600 MPa. A model involving hydrogen disentanglement from the lattice is proposed to explain the effects of abrasive polishing on the complete elimination of cracks and the generation of a compressive stress. This explanation is discussed in terms of the variations in properties of the coating with the rotation speed of the cathode.     

Expediency and human health: The regulation of environmental chromium

The complexity of chromium chemistry makes it an ideal example of how the Principle of Expediency, first articulated by sanitary pioneer Earle Phelps, can be used in a standard setting. Expediency, defined by Phelps as “the attempt to reduce the numerical measure of probable harm, or the logical measure of existing hazard, to the lowest level that is practicable and feasible within the limitations of financial resources and engineering skill”, can take on negative connotations unless subject to ethical guidance. In this paper we argue that without ethical principles as a rubric for negotiating environmental regulations, communities run the risk of slipping from the Principle of Expediency as defined by Phelps to the alternative usage of expediency meaning that which does not reflect ethical consideration or concern beyond self-serving interest. Three ethical ideals—justice, mercy and humility—are suggested as values to be considered while resolving regulatory issues related to environmental protection. The Principle of Expediency serves as a working principle, but not as a rigid algorithm, for setting regulatory limits for environmental concentrations of waste products like chromium. This paper is based on a dissertation submitted in partial fulfillment of the PhD degree by Lauren Bartlett, Duke University, 1997. An earlier version of this paper was presented at a mini-conference, Practicing and Teaching Ethics in Engineering and Computing, held during the Sixth Annual Meeting of the Association for Practical and Professional Ethics, Washington, D.C., March 8–9, 1997. This paper is one of a series edited by Michael C. Loui. See Volume 3, No. 4, 1997 for other papers in this series.