Lattice Distortion of High-entropy Alloys
Presented by NETL at World Congress on High Entropy Alloys (HEA 2019), 11/19
Gao, Michael C↗
Engineering topics
Liaw, Peter K
Publications and source records attributed to Liaw, Peter K.
Experiments and Model for Serration Statistics in Low-Entropy, Medium-Entropy, and High-Entropy Alloys
High-entropy alloys (HEAs) are new alloys that contain five or more elements in roughly equal proportion. We present new experiments and theory on the deformation behavior of HEAs under slow stretching (straining), and observe differences, compared to conventional alloys with fewer elements. For a specific range of temperatures and strain-rates, HEAs deform in a jerky way, with sudden slips that make it difficult to precisely control the deformation. An analytic model explains these slips as avalanches of slipping weak spots and predicts the observed slip statistics, stress-strain curves, and their dependence on temperature, strain-rate, and material composition. The ratio of the weak spots’ healing rate to the strain-rate is the main tuning parameter, reminiscent of the Portevin-LeChatellier effect and time-temperature superposition in polymers. Our model predictions agree with the experimental results. The proposed widely-applicable deformation mechanism is useful for deformation control and alloys design.
36 MATERIALS SCIENCE↗
Deformation mechanisms in a precipitation-strengthened ferritic super alloy revealed by in situ neutron dffraction studies at elevated temperatures
The ferritic superalloy Fe–10Ni–6.5Al–10Cr–3.4Mo strengthened by ordered (Ni,Fe)AlB2-type precipitates is a candidate material for ultra-supercritical steam turbine applications above 923 K. Despite earlier success in improving its room-temperature ductility, the creep resistance of this material at high temperatures needs to be further improved, which requires a fundamental understanding of the high-temperature deformation mechanisms at the scales of individual phases and grains. In situ neutron diffraction has been utilized to investigate the lattice strain evolution and the microscopic load-sharing mechanisms during tensile deformation of this ferritic superalloy at elevated temperatures. Finite-element simulations based on the crystal plasticity theory are employed and compared with the experimental results, both qualitatively and quantitatively. Based on these interphase and intergranular load-partitioning studies, it is found that the deformation mechanisms change from dislocation slip to those related to dislocation climb, diffusional flow and possibly grain boundary sliding, below and above 873 K, respectively. Insights into microstructural design for enhancing creep resistance are also discussed.
nuclear (including radiation effects), defects, me↗
Microstructures and properties of high-entropy alloys
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Zhang, Yong↗
Foreword Neutron and X-Ray Diffraction Studies of Advanced Materials VI - Centennial and Beyond
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Barabash, Rozaliya↗