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首页> 外文期刊>Materials Science and Engineering >Mechanical properties of ground state structures in substitutional ordered alloys: High strength, high ductility and high thermal stability
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Mechanical properties of ground state structures in substitutional ordered alloys: High strength, high ductility and high thermal stability

机译：替代有序合金中基态结构的机械性能：高强度，高延展性和高热稳定性

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摘要

We have studied the effect of atom arrangements in the ground state structures of substitutional ordered alloys on their mechanical properties using nickel-molybdenum-based alloys as model systems. Three alloys with nominal compositions of Ni-19.43 at% Mo, Ni-18.53 at% Mo-15.21 at% Cr and Ni-18.72 at% Mo-6.14 at% Nb are included in the study. In agreement with theoretical predictions, the closely related Pt_2Mo-type, DO_(22) and D1_a superlattices with similar energies are identified by electron diffraction of ground state structures, which can directly be derived from the parent disordered fcc structure by minor atom rearrangements on {420}_(fcc) planes. The three superlattices are observed to coexist during the disorder-order transformation at 700 ℃ with the most stable superlattice being determined by the exact chemical composition. Although most of the slip systems in the parent disordered fcc structure are suppressed, many of the twinning systems remain operative in the superlattices favoring deformation by twinning, which leads to considerable strengthening while maintaining high ductility levels. Both the Pt_2Mo-type and DO_(22) superlattices are distinguished by high strength and high ductility due to their nanoscale microstructures, which have high thermal stability. However, the D1_a superlattice is found to exhibit poor thermal stability leading to considerable loss of ductility, which has been correlated with self-induced recrvstallization by migration of grain boundaries.
机译：我们已经使用镍钼基合金作为模型系统研究了有序有序合金基态结构中原子排列对其机械性能的影响。研究中包括三种标称成分为Ni-19.43 at％Mo，Ni-18.53 at％Mo-15.21 at％Cr和Ni-18.72 at％Mo-6.14 at％Nb的合金。与理论预测一致，通过基态结构的电子衍射确定了具有相似能量的密切相关的Pt_2Mo型，DO_（22）和D1_a超晶格，这些基态可以通过{ 420} _（fcc）平面。观察到三个超晶格在700℃的无序转变过程中共存，最稳定的超晶格由确切的化学组成决定。尽管母体无序fcc结构中的大多数滑移系统都受到抑制，但许多孪生系统仍在超晶格中起作用，有利于通过孪生变形，从而在保持较高延展性的同时提高了强度。 Pt_2Mo型和DO_（22）超晶格均具有高强度和高延展性，这归因于它们的纳米级微观结构，具有很高的热稳定性。然而，发现D1_a超晶格表现出较差的热稳定性，导致相当大的延展性损失，这已与晶界迁移引起的自诱导结晶化有关。

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