On the temperature dependent strengthening of nickel by transition metal solutes

Fundamental insights are presented into the factors influencing the temperature-dependent strengthening of nickel by transition metal solutes. Strain rate jump tests are used using the alloying elements Ta, W and Re which lie beside one another in the d-block. At 800 °C, the hardening induced by Ta is significantly greater than that by W and Re. At T ≥ 1000 °C, Re becomes more potent than Ta at slow strain rates; at 1200 °C it is the most effective at all the strain rates employed. The results are interpreted using theory for temperature-dependent strengthening that emphasises solute-dislocation interaction. It is confirmed that at low temperatures the solute strengthening is controlled by paraelastic interaction - the solute with the largest size difference with the host Ni is the most potent. At higher temperatures, the evidence indicates that solutes collect on dislocations such that the slowest diffusing solutes confer maximal resistance to dislocation glide and climb; thus Re is particularly potent. The findings elucidate the role of transition metal solutes in strengthening. Moreover, they provide the necessary quantitative data for ongoing alloy design efforts.

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