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Recovery in cold-worked tungsten

Authors
Journal
Journal of the Less Common Metals
0022-5088
Publisher
Elsevier
Publication Date
Volume
3
Issue
5
Identifiers
DOI: 10.1016/0022-5088(61)90016-9

Abstract

Abstract Recovery in cold-worked powder metallurgy tungsten of two different purity levels was investigated by means of dislocation etch-pitting, accompanied by tensile measurements at 600°C, hardness measurements at room temperature, and X-ray back reflection. It was found that polygonization and subgrain coarsening in high-purity tungsten occurred readily at relatively low annealing temperatures. Above 1100°C strain-induced grain boundary migration occurred extensively in addition to subgrain coarsening. The presence of 25–63 weight p.p.m. of aluminum had a large effect in retarding polygonization and subgrain growth and raised the recrystallization temperature from 1400°C to 1800°C. However, strain-induced grain boundary migration was insensitive to the presence of aluminum at this concentration. Tensile measurements at 600°C showed that the subgrain size played a dominant role in the recovery of yield stress. Furthermore, the variation of the lower yield stress with subgrain diameter in annealed but unrecrystallized specimens obeyed the Petch equation σ Ly = σ 0 + k Yd − 1 2 , giving a value of 3.3·10 7 dynes/cm 3 2 for k Y . This suggests that the subgrain boundaries behave much in the same way as the grain boundaries in acting as barriers for dislocations.

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