However, X-ray-based measurements provide relatively low analytical capabilities, restricting the experimental observation of CSROs in the individual grains of the materials, as they are averaged over a comparatively large volume of material 16. Meanwhile, increasing the degree and spatial extent of the CSROs can strengthen fcc solid solutions by activating the planarity of dislocation slip and by modifying the strain hardening capacity 16, 23, 27.Įxtensive efforts to monitor the ordering transition in MPEAs have provided insights into the thermally induced CSROs via simulations 14, 15, 26 and X-ray absorption 30. This effect drives the non-random system towards ideal random, referred to as the ‘deformation-derived CSRO-to-disorder transition’. It has been widely conjectured that localised planar slip and leading dislocations would destroy the pre-existing CSRO domains in a face-centred-cubic (fcc) phase upon loading, which corresponds to the so-called glide plane softening 31, 32. Such ordering influences the dynamics of structural defects (primarily, dislocations) as well as the macroscopic mechanical, thermal, and functional properties of concentrated solid solutions including most MPEAs 24, 25, 26, 27, 28, 29, 30. The formation of diffusion-mediated CSRO domains in fully disordered alloys belongs to the category of thermally activated isostructural disorder-to-order transition at short ranges. short-range order (SRO), often called chemical SRO (CSRO) 22, 23. When compositionally homogeneous structures have specific low-coordination-number clusters, the preferential local ordering of principal elements generally dominates over the spatial order of a few nearest-neighbour spacings, i.e. However, several studies have indicated that the large-enthalpy interactions among the constituent species can drive a few MPEA systems towards inherent chemical ordering at nanometric scales, as suggested by the results obtained using the computational simulations 14, 15 and experimental methods 16, 17, 18, 19, 20, 21. Unlike traditional metallic alloys, MPEAs are concentrated solid solutions comprising mixtures of elements in which the atoms of principal elements tend to be distributed randomly. At the core of the interest lies their potential for achieving the requirements, for example, near-infinite alloy compositions at elevated temperatures 4, 5, 6, 7, 8, 9, 10, 11, 12, 13. Multi-principal-element alloys (MPEAs), the so-called medium- or high-entropy alloys (MEAs or HEAs, respectively), have received considerable interest. Here, we show that underpinned by molecular dynamics, MSRO in the alloys with low stacking-fault energies forms when loaded at 77 K, and these systems that offer different perspectives on the process of strain-induced ordering transition are driven by crystalline lattice defects (dislocations and stacking faults).įuture industrial development requires sustainable metallic alloys with an outstanding synergy between strength and ductility 1, 2, 3, particularly under extreme conditions. Scanning and high-resolution transmission electron microscopy and the anlaysis of electron diffraction patterns revealed the microstructural features responsible for MSRO and the dependence of the ordering degree/extent on the applied strain rates. The mechanical response and multi-length-scale characterisation pointed to the minor contribution of MSRO formation to yield strength, mechanical twinning, and deformation-induced displacive transformation. Unlike thermally activated ordering, mechanically derived short-range order (MSRO) in a multi-principal-element Fe 40Mn 40Cr 10Co 10 (at%) alloy originates from tensile deformation at 77 K, and its degree/extent can be tailored by adjusting the loading rates under quasistatic conditions. Chemical short-range order in disordered solid solutions often emerges with specific heat treatments.
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