The microstructures of the different types of steel comprise a variety of grain sizes, and grain size impacts an alloy's mechanical properties. For example, the schematic in Fig. 1 portrays the grains found in a dual-phase (DP) advanced high-strength steel (AHSS). The grains making up the ferrite phase have two important, controlling features - the boundaries and cores of the grain. The grain boundaries are stronger than the cores, so to increase the strength of the steel, smaller grains are formed to reduce the size of the weaker cores. This increases the volume of the stronger grain boundaries. Grain size depends on the available heat.
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