Synopses & Reviews
The laser is an ideal tool for surface treatment. Radiant energy is absorbed in the top few layers of an opaque material, where it can heat the surface or excite the surface atoms, leading to pyrolytic or photolytic processes. Laser irradiation is also chemically clean. The principal industrial advantages of laser surface treatment are: the thermally affected region is easily controlled in terms of depth, extent and time due to the ease with which the energy can be shaped and switched; the process is chemically clean; there is no need to touch the workpiece; automation is usually possible due to the absence of environmental disturbance while the radiant energy is delivered to the process: in-process sensing and control is therefore facilitated. With these significant advantages it is surprising to discover that the industrial use of the laser for surface treatment has been slow to take off. Possibly this may be simply due to the lack of engineers sufficiently fluent in laser applications. What one needs is a critical mass of such people, which is something to look forward to. Laser Processing: Surface Treatment and Film Deposition makes a major contribution to the recruitment of such talented persons.
Synopsis
Synthesis of nonequilibrium metallic phases has been an area of great interest to the materials processing community since early 1960. Inherent rapid cooling rates in laser processing are being used to engineer non-equilibrium microstructures which cannot be rivaled by other processes. This lecture will discuss the phenomena involved and its application in designing materials with tailored properties. What is non-equilibrium Synthesis? This is a synthesis method to produce binary or higher order materials where kinetics of the pro- cess affects the transport of the constituent elements during phase transformation resulting in a composition or crystallographic configuration which is different from what is observed when the elements arranges themselves with the lowest possible Gibbs Free energy, which is the equilibrium condition. Figure 1 illustrates the phenomena. Phase diagram under equilibrium condition is illustrated by the solid line whereas the no-equilibrium phase diagram is represented by the dotted line. One can observe the shrinkage of the phase field under non-equilibrium condition. Any alloy composition between the solidus lines of the equilibrium and non-equilibrium phase diagram will be a non- equilibrium alloys with extended solid solution.