Metastable Precipitates and their Misfit Strains in a Cu-0.9wt%Be Single Crystal
The precipitation processes from G.P. zones to γ’ in a Cu−0.9wt%Be alloy single crystal containing only the G.P. zones parallel to the matrix (001)α plane are investigated by high-resolution electron microscopy. The precipitate phases follow a G.P. zone → γ” → γI + γ’ sequence. The G.P. zone to γI phase transformation occurs successively via γ” during aging, while the γ’ phase heterogeneously precipitates on the γI phase. From length-change measurements during aging, the misfit strains of γ’ precipitates in directions perpendicular and parallel to α are estimated as ε11 =ε22 = −0.03 and ε33 = −0.09, respectively. The observation that the estimated absolute value of ε33 is much smaller than that of ε33 = −0.25 calculated using lattice parameters of the γ’ phase and Cu matrix is understood in terms of the relaxation of ε33 by interfacial misfit dislocations.
Young Won Chang, Nack J. Kim and Chong Soo Lee
R. Monzen et al., "Metastable Precipitates and their Misfit Strains in a Cu-0.9wt%Be Single Crystal", Materials Science Forum, Vols. 561-565, pp. 2297-2300, 2007