Metals cooling rates

Using rapid solidification technology molten metal is quench cast at a cooling rate up to 10 °C/s as a continuous ribbon. This ribbon is subsequently pulverized to an amorphous powder. RST powders include aluminum alloys, nickel-based superalloys, and nanoscale powders. RST conditions can also exist in powder atomization. 

To make martensite in pure iron it has to be cooled very fast at about 10 °C s h Metals can only be cooled at such large rates if they are in the form of thin foils. How, then, can martensite be made in sizeable pieces of 0.8% carbon steel As we saw in the "Teaching Yourself Phase Diagrams" course, a 0.8% carbon steel is a "eutectoid" steel when it is cooled relatively slowly it transforms by diffusion into pearlite (the eutectoid mixture of a + FejC). The eutectoid reaction can only start when the steel has been cooled below 723°C. The nose of the C-curve occurs at = 525°C (Fig. 8.11), about 175°C lower than the nose temperature of perhaps 700°C for pure iron (Fig. 8.5). Diffusion is much slower at 525°C than it is at 700°C. As a result, a cooling rate of 200°C s misses the nose of the 1% curve and produces martensite. 

Borides Metal solvent, Atomic ratio Max. and corresponding time Cooling rate ... 

Method Droplet Size ( im) Metal/AUoy Cooling Rate (°C/s) Throughput (kg/mm) Capacity (Metric Tons) Advantage Limitation... 

This process, originally designated as RSR (rapid solidification rate), was developed by Pratt and Whitney Aircraft Group and first operated in the late 1975 for the production of rapidly solidified nickel-base superalloy powders.[185][186] The major objective of the process is to achieve extremely high cooling rates in the atomized droplets via convective cooling in helium gas jets (dynamic helium quenching effects). Over the past decade, this technique has also been applied to the production of specialty aluminum alloy, steel, copper alloy, beryllium alloy, molybdenum, titanium alloy and sili-cide powders. The reactive metals (molybdenum and titanium) and... 

---