Influence of Elastic Energies on the Changes in Precipitation Structures in Fe-Base Ordering Alloys.

(1)在弱约束体系中，如Fe-Al-Ge中的D0_3，粒子作为时效时间t的立方根而粗化，即所谓的t^1/3定律成立，并且粒度分布根据平均粒度进行标度。(2)在Fe-Al-V中的D0_3、Fe-Si-V中的D03和Fe-Al-Co中的B2等强约束体系中，颗粒粗化的速度慢于LSW理论的预测，标度律不成立。此外，有时还观察到单个粒子分裂成二重态或八重态。(3)在强约束系统中，这种异常的粗化行为只能用新的粗化理论--分叉理论来解释。在分叉理论中，粗化的驱动力不仅是表面能，而且是弹性能。(4)铁基合金中共格沉淀的粗化行为与镍基合金中的伽马‘相非常相似。无论晶体结构如何，弹性约束系统所特有的反常行为很可能是普遍存在的。(5)通过控制弹性约束，即晶格失配与表面能之比，很有可能获得结构高度稳定的两相合金。

(1) In weakly constrained systems such as D0_3 in Fe-Al-Ge, particles coarsen as the cube root of the ageing time t, i.e. the so-called 't^<1/3>-law' holds, and the size distribution is scaled with respect to the mean particle size. The coarsening obeys the conventional coarsening theory such as the LSW theory of Ostwald ripening.(2) In strongly constrained systems such as D0_3 in Fe-Al-V, D0_3 in Fe-Si-V and B2 in Fe-Al-Co, the particle coarsening proceeds more slowly than the prediction of the LSW theory, and the scaling rule does not hold. Furthermore, the splitting of single particle into a doublet or to the octet is sometimes observed.(3) Such unusual coarsening behavior in strongly constrained systems can only be explained by the new coarsening theory named Bifurcation theory in which not only the surface energy but also the elastic energies are considered as the driving force for coarsening.(4) Coarsening behavior of coherent precipitates in Fe-base alloys is quite similar to that of gamma'-precipitates in Ni-base alloys. It is very likely that unusual behavior peculiar to the elastically constrained systems should be universal regardless of crystal structure.(5) It is very likely that the two-phase alloys having highly stable structure can be obtained with controlling the elastic constraint, i.e. the ratio of lattice misfit to surface energy.