Explain three three types of plate boundary
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11.2.5 Effect of boron
The ability of B to interact with diffusing atoms on grain boundary planes such that grain boundary diffusion is curtailed is one of the attractive features of this element. Abe (2006) has shown that grain boundary diffusion rates in an Fe–9Cr–3Co–3 W alloy with small amounts of nitrogen are reduced, with the effect being manifested in a reduced M23X6 precipitation rate, and a corresponding increase in creep life is obtained. Boron additionally assists in retarding the formation of fine grain size regions in welds (Abe, 2006). These are responsible for type IV cracking and when B is added to the above steel, the occurrence of type IV cracking can be eliminated. This effect is presumably connected with the influence of boron on the dynamic recrystallisation in the boundary neighbourhood mentioned in the previous section. To complete the boron story, the intragranular precipitation may be stabilised against coarsening by limitation of diffusion between coarsening particles (Golpayegani et al., 2003).