Effect of Grain Size on Mechanical Properties of Single Phase Co-Ni-Cr-Mo Based Superalloy

Abstract:

A recrystallized Co-Ni-Cr-Mo based superalloy was produced by cold working of 72% and subsequent recrystallization heat treatment. Microstructural observation revealed that a full recrystallization of the cold-worked alloy occured when heat treatment was performed at and above 1273K for 1h. So that, recrystallization heat treatment was carried out in a temperature range from 1273K to 1473K for 1h~24h, by which the average grain size was controlled to 28µm～238µm. Tensile tests were carried out from room temperature (RT) to 1073K in order to understand the effect of grain size on the mechanical properties of the Co-Ni-Cr-Mo based superalloy. At RT and 943K, yield strength, tensile strength and elongation of the recrystallized alloy were improved with decreasing grain size. The alloy having a grain size less than 42µm exhibited a steady-state flow behavior in the true stress-true strain curve at 943K. However, the alloy having a grain size of 28µm showed lower yield strength than that of 42µm at 1073K. It was found that the steady state flow is closely related to the occurrence of {111}<112> deformation twinning in the Co-Ni-Cr-Mo based superalloy.

• Periodical: Materials Science Forum (Volumes 475-479)
• Pages: 631-634
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.475-479.631
• Online since: January 2005
• Authors: Jun Kyung Sung, Mok Soon Kim, Won Yong Kim, Akihiko Chiba
• Keywords: Cobalt Based Alloy, Cold Working, Deformation Twinning, Mechanical Property, Recrystallization, Serrated Flow, Superalloy

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