Strain Rate Contribution due to Dynamic Recovery of Ultrafine-Grained Cu–Zr as Evidenced by Load Reductions during Quasi-Stationary Deformation at 0.5 <i>T</i><sub>m</sub>
oleh: Wolfgang Blum, Jiři Dvořák, Petr Král, Philip Eisenlohr, Vaclav Sklenička
| Format: | Article |
|---|---|
| Diterbitkan: | MDPI AG 2019-10-01 |
Deskripsi
During quasi-stationary tensile deformation of ultrafine-grained Cu-0.2 mass%Zr at 673 <inline-formula> <math display="inline"> <semantics> <mi mathvariant="normal">K</mi> </semantics> </math> </inline-formula> and a deformation rate of about 10<sup>−4</sup> s<sup>−1</sup> load changes were performed. Reductions of relative load by more than about 25% initiate anelastic back flow. Subsequently, the creep rate turns positive again and goes through a relative maximum. This is interpreted by a strain rate component <inline-formula> <math display="inline"> <semantics> <msup> <mover accent="true"> <mi>ϵ</mi> <mo>˙</mo> </mover> <mo>−</mo> </msup> </semantics> </math> </inline-formula> associated with dynamic recovery of dislocations. Back extrapolation indicates that <inline-formula> <math display="inline"> <semantics> <msup> <mover accent="true"> <mi>ϵ</mi> <mo>˙</mo> </mover> <mo>−</mo> </msup> </semantics> </math> </inline-formula> contributes the same fraction of <inline-formula> <math display="inline"> <semantics> <mrow> <mo>(</mo> <mn>20</mn> <mo>±</mo> <mn>10</mn> <mo>)</mo> <mo>%</mo> </mrow> </semantics> </math> </inline-formula> to the quasi-stationary strain rate that has been reported for coarse-grained materials with high fraction of low-angle boundaries; this suggests that dynamic recovery of dislocations is generally mediated by boundaries. The influence of anelastic back flow on <inline-formula> <math display="inline"> <semantics> <msup> <mover accent="true"> <mi>ϵ</mi> <mo>˙</mo> </mover> <mo>−</mo> </msup> </semantics> </math> </inline-formula> is discussed. Comparison of <inline-formula> <math display="inline"> <semantics> <msup> <mover accent="true"> <mi>ϵ</mi> <mo>˙</mo> </mover> <mo>−</mo> </msup> </semantics> </math> </inline-formula> to the quasi-stationary rate points to enhancement of dynamic recovery by internal stresses. Subtraction of <inline-formula> <math display="inline"> <semantics> <msup> <mover accent="true"> <mi>ϵ</mi> <mo>˙</mo> </mover> <mo>−</mo> </msup> </semantics> </math> </inline-formula> from the total rate yields the rate component <inline-formula> <math display="inline"> <semantics> <msup> <mover accent="true"> <mi>ϵ</mi> <mo>˙</mo> </mover> <mo>+</mo> </msup> </semantics> </math> </inline-formula> related with generation and storage of dislocations; its activation volume is in the order expected from the classical theory of thermal glide.