Crack Propagation and Crack Branching of High Strength Steels in Liquid Zinc Embrittlement

Abstract

The constant tensile speed tests were carried out in liquid zinc and in air on the precracked specimens of alloyed tool steel (JIS: SKD6) quenched and tempered at 923K, in order to investigate the crack propagation and crack branching behaviors in a liquid zinc embrittlement. The unstable fracture occurred at smaller load in liquid zinc than in air in all the testing temperatures. Grain boundary fracture occurred in liquid zinc, and fine zinc particles were observed on the fracture surface, which suggested that the adsorption of zinc vapor to a crack tip was the reason for such an unstable crack propagation. The crack propagation velocity in liquid zinc took a minimum at a certain temperature. The crack branching was often observed during the crack propagation in liquid zinc. Well-developed crack branching occurred when the temperature was low and the crack propagation velocity was high. © 1988, The Society of Materials Science, Japan. All rights reserved.