| Sputter-deposition was used to process nonequilibrium Cu-W alloys. A fundamental understanding of the microstructural transformations was investigated by studying the effects of annealing, alloying, and ion bombardment on crystal structure, phase formation, particle size and distribution, and grain size. Cu-W alloys were analyzed using energy dispersive x-ray analysis (EDX), electron probe microanalysis (EPMA), x-ray diffraction (XRD), transmission electron microscopy (TEM), and nanoindentation hardness testing.; Although the nearly total immiscibility of Cu and W in the liquid and solid states prevents the formation of Cu1-xWx alloys by conventional solidification processing by using the ultra-rapid equivalent quench rates (∼1014°C/s) characteristic of physical vapor-deposition processes, non-equilibrium Cu-W alloy films 15–20 microns thick were synthesized by do magnetron sputter-deposition from elemental Cu and W targets.; XRD lattice parameter measurements confirmed that these films were indeed “alloys” since nearly all W was in solution. XRD analysis shows that the as-deposited alloys exists as a FCC solid solution. Annealing treatments at 300°C and 600°C for up to 10 hours produced no detectable micro structural changes, but annealing for 35 minutes at 900°C caused the formation of the equilibrium BCC W phase and a decrease of W in solid solution. TEM of the annealed materials revealed a high density of discrete, nanoscale BCC W particles dispersed internally and along the boundaries of the Cu grains. Annealing for times up to 100 hours caused the W particles to coarsen while the Cu matrix grains remained refined below 300 nm. An orientation relationship consistent with the Kurdjumov-Sachs (K-S) and the related Nishiyama-Wasserman (N-W) relationship was observed in samples annealed at 900°C for 1 hour.; TEM of the annealed W content in Cu87W3, and Cu 79W21 alloys revealed that increased W content causes an increase in W particle size due to increased W solute. Increasing ion bombardment by applying a substrate bias voltage in Cu97W3 and Cu 79W21 films accelerated the formation of the equilibrium BCC W phase in the as-deposited alloys and decreased the amount of W in solid solution. |
