Rapid cooling process

Y. Xue-hua, L. Rang-su, T. Ze-an, H. Zhao-yang, L. Xiao-yang, Z. Qun-yi. Formation and evolution properties of clusters in liquid metal copper during rapid cooling processes. Trans. Nonferrous Met. Soc. China, N18, pp. 33-39 (2008). 

Traditionally, production of metallic glasses requites rapid heat removal from the material (Fig. 2) which normally involves a combination of a cooling process that has a high heat-transfer coefficient at the interface of the Hquid and quenching medium, and a thin cross section in at least one-dimension. Besides rapid cooling, a variety of techniques are available to produce metallic glasses. Processes not dependent on rapid solidification include plastic deformation (38), mechanical alloying (7,8), and diffusional transformations (10). 

Because this reaction is highly exothermic, the equiUbrium flame temperature for the adiabatic reaction with stoichiometric proportions of hydrogen and chlorine can reach temperatures up to 2490°C where the equiUbrium mixture contains 4.2% free chlorine by volume. This free hydrogen and chlorine is completely converted by rapidly cooling the reaction mixture to 200°C. Thus, by properly controlling the feed gas mixture, a burner gas containing over 99% HCl can be produced. The gas formed in the combustion chamber then flows through an absorber/cooler to produce 30—32% acid. The HCl produced by this process is known as burner acid. 

Is the component subject to a rapid cooling rate from a high temperature and/or sustained high temperature during processing (e.g. >0.57m) (5)... 

Rapid cooling can cause residual stresses (leading to accelerated corrosion), distortion and quench cracks. The orientation of the component during processing is important in this respect. Sustained high temperatures can cause warping and softening. 

The properties of the nylons are considerably affected by the amount of crystallisation. Whereas in some polymers, e.g. the polyacetals and PCTFE, processing conditions have only a minor influence on crystallinity, in the case of the nylons the crystallinity of a given polymer may vary by as much as 40%. Thus a moulding of nylon 6, slowly cooled and subsequently annealed, may be 50-60% crystalline, while rapidly cooled thin-wall mouldings may be only 10% crystalline. 

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