Effect of temperature and strain rate on serrated flow behaviour of Hastelloy X

Serrated flow behaviour of Hastelloy X has been examined over a wide range of temperature (300–1023 K) and strain rate (3 × 10−3s−1 to 3 × 10−5s−1). The alloy exhibited different types of tensile serrated flow in the intermediate temperature range of 473–923 K. Normal portevin-Le Chatelier effect (PLE) exhibiting type A and B serrations were observed at temperatures less than 823 K and inverse PLE exhibiting type C serrations was noticed at temperatures above 823 K. The average activation energy value of 106 kJ mol−1 for the A and B types of serrated flow has been evaluated. The evaluated activation energy value revealed that the migration of molybdenum in the nickel matrix has been found to be responsible for the occurrence of serrated flow in the alloy.

► Tensile serrated flow behaviour of Hastelloy X was examined.
► A, A + B, B and C types of serrated flow behaviour have been observed.
► Molybdenum solute has been found to be responsible for serrated flow behaviour.
► M6C, M23C6 and σ-phase were observed at higher temperatures.