Microstructure and strengthening mechanism of Ni sub(3)Al intermetallic compound

• Published in: Metals and materials international 2013-09, Vol.19 (5), p.941-948
• Main Authors: Oh, Chang-Sup, Han, Chang-Suk
• Format: Article
• Language: English
• Subjects: Cross slip; Dislocations; Intermetallic compounds; Intermetallics; Nickel aluminides; Precipitates; Precipitation; Precipitation hardening; Strength
• ISSN: 1598-9623; 2005-4149
• DOI: 10.1007/s12540-013-5006-2

Structural studies have been performed on precipitation hardening found in Ni sub(3)Al-base ordered alloys using transmission electron microscopy. The gamma ' phase hardens appreciably by the fine precipitation of disordered gamma . The strength of gamma ' increases over the temperature range of experiment by the precipitation of fine gamma particles. The peak temperature where a maximum strength was obtained shifted to higher temperature. Superlattice dislocations dissociate into fourfold Shockley partial dislocations in a uniform supersaturated solid solution of the gamma ' phase. Dislocations are attracted into the disordered gamma phase and dissociate further in the particles. At any stage of aging, dislocations cut through the particles and the Orowan bypassing process does not occur even in the overaged stage of this alloy system. When the applied stress is removed, the dislocations make cross slip into (010) plane, while those in gamma precipitates remain on the (111) primary slip plane. The increase of high temperature strength in gamma ' containing gamma precipitates is due to the restraint of cross slip of dislocations from (111) to (010) by the dispersion of disordered gamma particles. The orientation dependence of strength is decreased by the fine precipitation of a disordered gamma phase.