Surface Nanostructuring of a CuAlBe Shape Memory Alloy Produces a 10.3 ± 0.6 GPa Nanohardness Martensite Microstructure

Severe plastic deformation (SPD) has led to the discovery of ever stronger materials, either by bulk modification or by surface deformation under sliding contact. These processes increase the strength of an alloy through the transformation of the deformation substructure into submicrometric grains o...

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Bibliographic Details
Published in:Materials 2020-12, Vol.13 (24), p.5702
Main Authors: Figueroa, Carlos Gabriel, Jacobo, Víctor Hugo, Cortés-Pérez, Jacinto, Schouwenaars, Rafael
Format: Article
Language:English
Subjects:
Adhesive wear
Alloys
Austenite
Coefficient of friction
Crack initiation
Ferrous alloys
Hot rolling
Martensite
Martensitic transformations
Metal fatigue
Microscopy
Microstructure
Nanohardness
Nonferrous alloys
Plastic deformation
Recrystallization
Shape memory alloys
Sliding contact
Strain hardening
Substructures
Surface hardness
Topography
Ultrafines
Wear resistance
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Summary:Severe plastic deformation (SPD) has led to the discovery of ever stronger materials, either by bulk modification or by surface deformation under sliding contact. These processes increase the strength of an alloy through the transformation of the deformation substructure into submicrometric grains or twins. Here, surface SPD was induced by plastic deformation under frictional contact with a spherical tool in a hot rolled CuAlBe-shape memory alloy. This created a microstructure consisting of a few course martensite variants and ultrafine intersecting bands of secondary martensite and/or austenite, increasing the nanohardness of hot-rolled material from 2.6 to 10.3 GPa. In as-cast material the increase was from 2.4 to 5 GPa. The friction coefficient and surface damage were significantly higher in the hot rolled condition. Metallographic evidence showed that hot rolling was not followed by recrystallisation. This means that a remaining dislocation substructure can lock the martensite and impedes back-transformation to austenite. In the as-cast material, a very fine but softer austenite microstructure was found. The observed difference in properties provides an opportunity to fine-tune the process either for optimal wear resistance or for maximum surface hardness. The modified hot-rolled material possesses the highest hardness obtained to date in nanostructured non-ferrous alloys.
ISSN:1996-1944
1996-1944
DOI:10.3390/ma13245702