Dislocations in α-Brass single crystals fatigued at low stress amplitude

Abstract

Dislocation substructures of push-pull low-stress-fatigued a-brasses of different zinc contents were studied by transmission electron microscopy of thin foils parallel and perpendicular to tJhe slip plane. The general tendency of dislocations in pure copper is to form band structures. This tendency decreases with increasing zinc content. In Cu-30% Zn the dislocation structures consist of pile-ups plus a limited number of stacking faults which are observed on (111) planes. Both short-range and long-range stress fields are responsible for fatigue-hardening. The contribution of long-range stress fields to the total hardening decreases with increasing zinc content. All dislocation structures and mechanical properties confirm the strong influence of the stacking fault energy in the course of fatigue-hardening. Versetzungs-Subst.rukturen von a-Messing mit verschiedencm Zinkgehalt wurden nach schwacher Gegentakt-Ermudungsbelastung mittels Transmissions-Elektronenmikroskopie an diinnen Schichten parallel und senkrecht zur Gleitebene nntersucht. Jm allgemeinon bilden die Versetznngen in reinem Kupfer Randerstrukturen. Diese Tendznz nimmt mit steigendem Zinkgehalt ab. In einer Cu-301', Zn-Legierung bestehen die Versetzungsstrukturen aus Anfstapelungen und eincr begrenzten Zahl von Stapelfehlern, die auf (111)-Ebenen beobachtet wurden. Sowohl kurzreichweitige als auch langrzichweitige Spannungsfefder sind fur die Ermudungsverfestigung vcrantwortlich. ner Beitrag der fangreichweitigen Spannungsfelder auf die Gesamtverfestigung nimmt mit steigendem Zinkgehalt ab. Alle Versetzungstrukturen und mechanischrn Eigenscha€ten bestiitigen den groOen EinfluO der Stapelfehlerenergie im Verlauf der Ermudungsverfestigung.

Orientation dependence of dislocation structures in cyclically deformed Cu-16 At. Pct Al alloy single crystals

“…For example, the early work of Youssel [12] and Lukas and Klesnil [13,14] demonstrated that the ladder structures of PSBs, IN the past three decades, much development in underwhich can be seen often in cycled Cu single crystals, were standing the cyclic deformation mechanism of fcc single not found in Cu-30 at. pct Zn alloy single crystals fatigued crystals has occurred, and research was devoted mainly to under a stress-controlled condition, and that the dislocation wavy-slip pure metals.…”

“…They reported that primary behavior to become different from that of pure metals. [8,[10][11][12][13][14] edge dislocations dominate the structure at all stages of deformation, forming dipolar and multipolar arrays. With increasing stress level, the main change of dislocation struc- the strain burst occurred, the enlarged plastic-strain range can be recovered automatically into the controlled value by using a self-designed computer program.…”