The critical resolved shear stress of peak-aged aluminium–lithium single crystals

• Published in: Acta materialia 1999-04, Vol.47 (6), p.1953-1964
• Main Authors: Kalogeridis, A., Pesicka, J., Nembach, E.
• Format: Article
• Language: English
• Subjects: Aluminum alloys; Applied sciences; Condensed matter: structure, mechanical and thermal properties; Dislocations, mobility; Exact sciences and technology; Fatigue, brittleness, fracture, and cracks; Mechanical and acoustical properties of condensed matter; Mechanical properties of solids; Mechanical properties, plastic; Metals. Metallurgy; Phase transformation, growth; Physics; Transmission electron microscopy (TEM)
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/S1359-6454(99)00018-X

The critical resolved shear stress (CRSS) of single crystals of aluminium-rich aluminium–lithium alloys has been measured at 283 K. These alloys are strengthened by coherent precipitates of the metastable L1 2 long-range-ordered δ′ phase. The specimens had been subjected to long aging treatments such that they were in the peak-aged state. This contrasts with the earlier investigation (Schlesier and Nembach, Acta metall. mater., 1995, 43, 3983) in which underaged Al–Li single crystals have been studied. The contribution τ p of the δ′ precipitates to the present peak-aged specimens' total CRSS has been found to be a function only of the δ′ volume fraction f, i.e. τ p was independent of the radius of the δ′ precipitates. The experimental data τ p( f) are well represented by a relation which had been developed for the description of peak-aged γ′-strengthened nickel-base superalloys. These latter materials are isomorphous to δ′-strengthened Al-rich Al–Li alloys: coherent L1 2 long-range-ordered particles are embedded in a disordered f.c.c. matrix.