Creep and fracture of engineering materials and structures PDF

ABSTRACT

Examination of creep data alone cannot always provide clear evidence for the identification of the operative deformation mechanism. Such uncertainty has led to a prolonged debate on the role of diffusional flow processes during deformation under low stress at elevated temperatures. More definitive information can be obtained from associated microstructural observations since clear distinctions can then be drawn between the different effects arising from different modes of deformation. On this basis low stress creep tests have been carried out on OFHC copper and on a precipitate strengthened magnesium alloy (ZR55). Evidence is presented here involving the displacement of surface marker lines, changes in grain boundary profiles and redistribution of precipitates with respect to the orientation of the applied stress. Observation of these microstructural features has assisted in defining situations where creep occurs by directional diffusion in these materials. The critical characteristics of these features, produced during the accumulation of strain, such that they may be interpreted as evidence for diffusional flow, rather than for any alternative deformation mechanism, are indicated.

Edited by: J.D. Parker