Crystallographic aspects of the cellular precipitation reaction in copper-3 percent titanium

The interlamellar and growth interfaces in the cellular precipitation reaction in Cu-3wt%Ti were examined to determine the role of crystallography in this reaction. The (111){dollar}sb{lcub}rm Cu{rcub}Vert{dollar}(010){dollar}sb{lcub}rm Cu{lcub}sb4{rcub}Ti{rcub}{dollar} interlamellar habit plane was observed by high resolution TEM to be atomically flat. Both this habit plane and the habit plane of an observed growth interface were examined with the Theory of Ideal Interfacial Configurations.; Analysis of the interlamellar interfaces reveals misfit dislocations, structural ledges, direction steps, and intruder dislocations. These interfacial defects were mapped onto a projected O-lattice to determine their role in the relief of interfacial strain. This interfacial strain relief was accomplished by a different arrangement of these interfacial defects on each analyzed interface.; At small undercoolings, the cellular reaction front exhibits parallel faceting of the precipitate growth interfaces, which is inconsistent with the conventional view of the cellular reaction front as a disordered boundary. These facets often deviate from the orientation of the grain boundary, indicating a low energy interface between the Cu{dollar}sb4{dollar}Ti precipitate and the supersaturated matrix, and thus a deference to crystallography at the cellular growth front. Curvature of the reaction front usually results in the adoption of a different habit plane which is better aligned with the local grain boundary direction. A mechanism is proposed to explain the nucleation and observed morphologies of cellular precipitation at these small undercoolings.; Increased undercoolings result in a rapid decrease in crystallographic influence at the growth front. A 10{dollar}spcirc{dollar}C undercooling produces a high concentration of growth ledges at the growth interface, which indicate that growth of the cellular colony occurs by a cooperative mechanism. Curvature of the precipitate growth interface increases with increasing undercooling. The precipitate growth interfaces formed at undercoolings of 10{dollar}spcirc{dollar}C and 20{dollar}spcirc{dollar}C still tend to align themselves in a parallel direction, indicating a crystallographic orientation of even the curved interfaces. At undercoolings of 55{dollar}spcirc{dollar}C, the influence of crystallography is no longer observed. Growth interfaces produced at undercoolings of 100{dollar}spcirc{dollar}C and more are obscured by the presence of matrix {dollar}betaspprime{dollar} precipitates.