Mechanical properties of ultrafine-grain zirconium in the temperature range 4.2–300K

Abstract

The mechanical properties under uniaxial compression of cylindrical samples of ultrafine-grain (UFG) zirconium (grain size ∼0.4μm) obtained by intense plastic strain (IPS)—a combination of extrusion, annealing, and drawing—have been studied in the temperature range 4.2–300K. The mechanical characteristics of UFG zirconium have been studied in two structural states and the results are compared with each other as well as with the characteristics of coarse-grain polycrystals of this material (state 1—samples after IPS, state 2—samples after IPS and annealing). It has been established that grain-size reduction under IPS substantially increases the yield stress of polycrystals (by a factor of 6 at 300K and by a factor of 4 at 77K) while maintaining a large reserve of plasticity up to 15%. Two stages of strain hardening and a decrease of the plastic-flow activation volume with increasing strain has been recorded in the strain diagrams of UFG zirconium. It is concluded that the main mechanisms determining the yield stress and strain hardening are the same for ultrafine- and coarse-grain zirconium: intragrain dislocation slip and twinning occur in parallel and interact with one another.

Microstructure and Properties of Nanostructured Zirconium Processed by High Pressure Torsion

“…In last years several methods of severe plastic deformation (SPD) were developed and used to produce nanomaterial with unique physical properties [2]. New ultrafine grained and nanostructured states of Zr were achieved recently by various SPD methods, such as a combination of extrusion, annealing and wire drawing [3], ECAP [4], and HPT [5,6]. It was shown that nanograined Zr has an improved strength characteristics, which sometimes is even accompanied by appropriate plasticity [3,6].…”

In-situ TEM mechanical testing of nanocrystalline zirconium thin films

“…The Young's modulus value was measured to be about 87.6 MPa, which validates the satisfactory calibration of the procedure since the accepted value in the literature is about 90 GPa. The experimental results for the o10 nm grain size specimens show remarkable size effect when compared to the literature [3], especially in terms of plastic strain. For about 300 nm grain size [3], the observed plastic strain of 15% overshadows our observation of only 1.5% strain for 410 nm grain size.…”

“…The experimental results for the o10 nm grain size specimens show remarkable size effect when compared to the literature [3], especially in terms of plastic strain. For about 300 nm grain size [3], the observed plastic strain of 15% overshadows our observation of only 1.5% strain for 410 nm grain size. Such size effect could also emanate from the specimen (bulk nanocrystal vs thin film nanocrystal), since thin films have orders of magnitude higher surface area compared to the bulk.…”

“…Its strength, resistance to corrosion and irradiation, high melting point and biocompatibility are attractive features for important applications in nuclear, aviation and surgical implant industries. Even though nanocrystalline materials exhibit higher yield strength and resistance to fatigue [1,2], more comprehensive studies in the relevant literature are limited to ultra-fine (around 100 nm or larger) grain sizes [3,4]. These studies addressed the challenges in the nanocrystalline materials preparation through severe plastic deformation, surface mechanical attrition treatment or cryo-rolling [5,6].…”

Low-Temperatures Physical-Mechanical Properties of the Medium-Entropy Alloy Co$_{17.5}$Cr$_{12.5}$Fe$_{55}$Ni$_{10}$Mo$_5$

“…Як було відзначено, на деформаційних кривих за температур, близьких до 4,2 К, спостерігається зміна виду пластичного плину від плавного до стрибкоподібного. Відзначимо, що низькотемпературна стрибкоподібна деформація характерна для багатьох ГЦКстопів (як грубозернистих, так і наноструктурних [27,29]).…”