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Gradient Enhanced Strain Hardening and Tensile Deformability in a Gradient-Nanostructured Ni Alloy
Xinlai An1, Weikang Bao1, Zuhe Zhang1
1Herbert Gleiter Institute of Nanoscience, School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, China.
Nanomaterials (Basel, Switzerland)
|September 28, 2021
Summary
Gradient nanostructured materials exhibit unique properties. This study reveals that strain gradients within gradient nanostructures (GNS) cause extra strain hardening, enhancing uniform elongation in Ni alloys.
Area of Science:
- Materials Science
- Mechanical Engineering
- Nanotechnology
Background:
- Gradient nanostructured materials (GNS) feature spatial gradients in microstructure.
- The mechanical interplay between GNS surfaces and coarse-grained (CG) cores is understood.
- Mechanisms within GNS layers remain unclear.
Purpose of the Study:
- Investigate interactions between nanostructured layers within GNS.
- Determine the source of enhanced mechanical properties in GNS.
- Clarify the role of strain gradients in GNS behavior.
Main Methods:
- Microtension tests on a Ni alloy processed by surface mechanical rolling treatment.
- Testing of the whole GNS sample and three subdivided nanostructured layers at different depths.
- Analysis of depth-dependent mechanical performance and strain hardening.
Main Results:
- The topmost nanograined layer showed high strength but brittleness.
- Deeper nanostructured layers exhibited lower strength with increased tensile plasticity.
- The GNS sample's behavior aligned with the softer, inner nanostructured layers.
- An extra strain hardening effect was observed in the GNS sample, increasing uniform elongation.
Conclusions:
- Incompatibility between depth-dependent mechanical properties of nanostructured layers creates strain gradients.
- These strain gradients are responsible for the extra strain hardening and enhanced uniform elongation in GNS.
- Understanding these internal GNS mechanisms is crucial for designing advanced materials.
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