Slip Line Pattern and Active Slip Systems of Tungsten and Molybdenum Single Crystals Weakly Deformed in Tension at Room Temperature

Abstract

Electron zone-refined tungsten and molybdenum single crystals are deformed in tension a t room temperature. The slip systems on the cylinder-shaped tensile specimens are determined using the light as well as the electron microscope. The slip line pattern depends sensitively on the orientation of the stress axis. Single slip on the crystals investigated is not observed. The slip occurs preferentially on planes of type { 110}, but usually further slip planes of the <111> zone are also active. The slip band structure is discussed in terms of elementary slip processes.Elektronenzonengeschmolzene Wolfram-und Molybdln-Einkristalle wurden bei Raumtemperatur im Zugversuch verformt. Mittels licht-und elektronenmikroskopischer Methoden wurden die Gleitsysteme an den zylinderformigen Zugproben bestimmt. Das Gleitlinienbild war stark abhiingig von der Achsenorientierung. An den untersuchten Kristallen konnte keine Einfachgleitung beobachtet werden. Die Abgleitung erfolgte auf Ebenen vom Typ { 1103, aber meistens waren auch noch andere Gleitebenen der (111)-Zone wirksam. Die Gleitlinienstruktur wird in Verbindung mit elementaren Gleitprozessen diskutiert.

A detailed investigation of slip line pattern and subsurface dislocation structure of molybdenum single crystals

“…The slip line pattern was systematically examined by optical microscopy round the whole circumference of crystals. Electron micrographs of pre-selected surface areas were produced by a special C-Pt replica technique to obtain informations on the fine structure of slip and the active slip directions (for details see [12,19,201). For TEM observation of the crystal surface, thin foils were prepared from the flat tensile specimens by jet-electro-polishing from only one side up to perforation.…”

Dislocation junctions as indicators of elementary slip planes in body-centered cubic metals

“…At medium and high-temperatures, effective slip on f112g planes has been observed experimentally in all bcc metals (W [8], Mo [9], Ta [10], and Nb [11]). Slip on f123g planes has also been reported in W and Mo [7] and in a-Fe [12].…”

“…Such an uniaxial deformation experiment in which f112g or f123g slip systems are expected to be active should be conducted in an orientation close to one of the corners of the [001]-[011]-½ " 111 stereographic triangle since the Schmid factors of the f112g and f123g slip systems are higher there than the Schmid factor of the most favorable f110g slip system. The experiment should furthermore be conducted at medium or high temperatures because in this regime macroscopic f112g [5,17] and f123g slip [7,12,37] have been observed in several bcc metals. It must be emphasized that demonstrating the occurrence of even a single b ¼ ah100i junction along another direction than the h100i or h111i directions (Fig.…”

“…[7]). An underlying feature of macroscopic slip traces in all bcc metals is that up to the so-called athermal temperature T K , they are temperature dependent and vary from coarse crystallographic on welldefined planes f110g planes at low temperatures to non-planar or wavy at higher temperatures.…”

The Influence of Temperature on Slip Behaviour of Molybdenum Single Crystals Deformed in Tension in the Range from 293 to 573 °K .II. Slip Geometry and Structure of Slip Bands

“…Electron micrographs of preselected surface areas were made t o obtain informations on active slip directions, elementary slip processes, and fine structure of slip bands (for details see [3,10,111). Additionally, Laue X-ray back reflection measurements were carried out before and after tensile tests t o determine the paths of tensile axes.…”