Well-aligned in situ composites in directionally solidified Fe–Ni peritectic system

Well-aligned in situ composites obtained in directionally solidified Fe–Ni peritectic system are formed by nonisothermal cellular coupled growth instead of isothermal coupled growth because of morphological instabilities. Peritectic coupled growth, with a plane interface like eutectic coupled growth, is always unstable due to the influence of peritectic reaction around the liquid/δ∕γ trijunctions. However, cellular nonisothermal peritectic coupled growth, in which one of the two solid phases bulges towards the liquid ahead of the other one, can reach a steady state and produce well-aligned in situ composites under proper growth conditions and sample composition.