Mechanism of steady-state grain growth in aluminum

Abstract

Grain growth, defined as the increase in volume of the average grain, is found, in its steadystate, to be directly proportional to the time of isothermal annealing. During steady-state grain growth the grain corners are found all to be quadruple points, the grain edges all triple lines and the ratio of corners to faces to edges to be 6:7:12. The rate constant for steady-state grain growth is shown to be calculable from first principles and from properties that can be measured independently of the growth observation. It is the product of four individual constants, namely: 1) a dimensionless topological constant ⊝ that is characteristic of steady-state grain growth in any material, 2) the mobility ώ of the average grain boundary in the specific material, 3) the surface tension y of the average grain boundary in the specific material and 4) a dimensionless structural constant σ which expresses the curvature of surface of the grain boundary in the array of grain forms obtaining in the specific specimen of the material and which can be determined metallographically. The topological changes that constitute steady-state growth are shown to exist as a logical sequence of simple events.