Stacking-fault strengthening of biomedical Co–Cr–Mo alloy via multipass thermomechanical processing

Abstract

The strengthening of metallic biomaterials, such as Co–Cr–Mo and titanium alloys, is of crucial importance to the improvement of the durability of orthopedic implants. In the present study, we successfully developed a face-centered cubic (fcc) Co–Cr–Mo alloy with an extremely high yield strength (1400 MPa) and good ductility (12%) by multipass hot-rolling, which is suitable for industrial production, and examined the relevant strengthening mechanisms. Using an X-ray diffraction line-profile analysis, we revealed that a substantial increase in the number of stacking faults (SFs) in the fcc γ-matrix occurred at a greater height reduction (r), while physical modeling demonstrated that the contribution of the accumulated SFs (i.e., the reduction in SF spacing) with an increase in r successfully explains the entire strengthening behavior of the hot-rolled alloy. The present study sheds light on the importance of the SF strengthening mechanism, and will help to guide the design and manufacturing strategy for the high-strength Co–Cr–Mo alloys used in highly durable medical devices.

Effect of multiple laser shock processing on nano-scale microstructure of an aluminum alloy

“…Thus, the increase in stacking fault probability in 6061-T6 alloy will decreased the SFE after high strain rate deformation [55][56] . There are five main strengthening mechanism in the metallic materials: (i) solid-solution hardening, (ii) precipitation hardening, (iii) transformation hardening, (iv) dislocation hardening and (v) grain refinement [57][58] .…”

“…These inferences are in good agreement also with TEM observations. The XRD line-profile analysis is a capable technique the determining SF, crystallite size, lattice strain and dislocation density [5,57,60] . The SF strengthening, nanostructure and ultrafine grained microstructure were obtained after severe plastic deformation (SPD), equal channel angular pressing (ECAP), high-pressure torsion (HPT) and [61][62][63][64] .…”

Correlating work hardening with co-activation of stacking fault strengthening and transformation in a high entropy alloy using in-situ neutron diffraction

“…The activation of SF strengthening and transformation induced plasticity (TRIP) clearly provided real-time evidence of their cooperative behavior and contributions to simultaneous enhancement of strength and ductility. While the relationship between SF strengthening and SF interspacing was previously established [13][14][15] , we use in-situ neutron diffraction to capture this phenomenon in real time for the first time and demonstrate the combined importance of activating multiple deformation mechanisms to overcoming the strength-ductility tradeoff.…”

“…Beside the SF width, other characteristic structural dimensions such as the interspacing between two SFs, i.e. SF interspacing (L SF ), have been measured using X-ray diffraction (XRD) 13 . Importantly, the spacing between SFs has been correlated with increases in strength enhancement in various alloy systems.…”

“…Importantly, the spacing between SFs has been correlated with increases in strength enhancement in various alloy systems. Stacking fault strengthening (σ SF ) was studied in hexagonal close-packed (HCP) Mg 14, 15 alloys, FCC Cu-Al alloys 16 and FCC Co alloys 13 using TEM and XRD. These studies showed that the decrease in L SF corresponded to an increase in yield strength due to SF-dislocation interactions.…”