Effects of grain size and test temperature on ductility and fracture behavior of A B-doped Ni3Al alloy

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)22_Publication in policy or professional journal

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Original languageEnglish
Pages (from-to)1241-1249
Journal / PublicationActa Metallurgica
Volume36
Issue number5
Publication statusPublished - May 1988
Externally publishedYes

Abstract

Effect of grain size on ductility and fracture behavior of boron-doped Ni3Al (Ni-23A1-0.5Hf, at.%) was studied by tensile tests using a strain rate of 3.3 × 10-3 S-1 at temperatures to 1000°C under a high vacuum of <1 × 10-4 Pa. At temperatures below 700°C, the alloy showed essentially ductile transgranular fracture with more than 30% elongation whereas it exhibited ductile grain-boundary fracture in the temperature range from 700 to 800°C. In both cases, the ductility was insensitive to grain size. On the other hand, at temperatures above 800°C, the ductility decreased from about 17 to 0% with increasing grain size. The corresponding fracture mode changed from grain-boundary fracture with dynamic recrystallization to brittle grain-boundary fracture. The ductile transgranular fracture at lower temperatures is explained by stress concentration at the intersection of slip bands. The grain-size dependence of ductility is interpreted in terms of stress concentration at the grain boundaries. Finally, it is suggested that the temperature dependence of ductility in this alloy might be related to the thermal behavior of boron segregated to the grain boundaries. © 1988.