SEDL / STP / STP942-EB / STP24475S

Effects of Testing Method on Cyclic Hardening Behavior in Face-Centered-Cubic Alloys

Pickard, AC
Rolls-Royce plc., Derby,

Knott, JF
University of Cambridge,

Pages: 19    Published: Jan 1988

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Abstract

Several types of test methods are employed to evaluate the cyclic hardening behavior of engineering alloys. Three such tests are the plastic-strain limit (PSL) test, the multiple-step test (MST), and the incremental-step test (IST). In each type of test, the material experiences a different plastic-strain history prior to measurement of the saturation stress. The present paper examines effects of these different histories on cyclic hardening behavior in a number of face-centered-cubic (fcc) alloys, using all three types of test. For 316 stainless steel and a weldable Al-4.5Zn-2.5Mg alloy, behavior in the IST is similar to that in the MST. In a series of experiments carried out on Cu and Cu-Al alloys, significant differences between the different tests are observed; these are explained in terms of the dislocation substructures generated by the strain histories. Differences in behavior are also observed for Al-4.5Zn-2.5Mg in under-aged, peak-aged, and over-aged conditions; these are most pronounced for the under-aged alloy, where slip is planar.