Communication

Occurrence of plastic instabilities in dynamic microhardness testing
G. Bérces, N.Q. Chinh, A. Juhász, J. Lendvai
(Eötvös University)

Plastic instabilities were observed to appear during dynamic ultra microhardness testing of a solid solution Al-3.3 wt.%Mg alloy. The tests were carried out at room temperature with a Vickers hardness indenter in a computer controlled dynamic ultra microhardness testing machine. During the tests the applied load was increased from 0 to 2000 mN at constant loading rate. The instabilities appear as characteristic steps in the continuously recorded load-indentation depth curves. The physical basis for the occurrence of the instabilities is the interaction between moving dislocations and solute atoms, a phenomenon termed in the literature as serrated yielding, jerky flow or Portevin-Le Châtelier effect. The instabilities start at a critical load, F_c in the depth-load curve. Varying the loading rate, <>m, by two orders of magnitude F_c was found to increase linearly with the loading rate.
Keywords: alloys, intermetallic; mechanical properties; hardness testing
Order No.: JA806-001 © 1998 MRS

Go to June 1998 Table of Contents

Home •  News • Society Information •  Site Map • Comments • Search  • Contacts Meetings • Membership • Publications • Marketing Opportunities • Materials Connections Search the Site ©1995-2005 Materials Research Society 506 Keystone Drive Warrendale PA 15086-7573 USA Phone: 724.779.3003, Fax: 724.779.8313 General Information: Web site comments/questions: