Impact tension behavior of heavy-drawn nanocrystalline CoCrNi medium entropy alloy wire

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Structural materials : properties, microstructure and processing, 2022-10, Vol.856, p.144041, Article 144041
• Main Authors: Qiao, Yu, Cao, Fu-Hua, Chen, Yan, Wang, Hai-Ying, Dai, Lan-Hong
• Format: Article
• Language: English
• Subjects: Alloys; Cryogenic temperature; Ductility; Entropy; Fixtures; High entropy alloy; High entropy alloys; High strain rate; High strength alloys; Impact loads; Low temperature; Mechanical properties; Medium entropy alloys; Molecular dynamics; Plastic deformation; Split hopkinson tension bar; Strain rate; Temperature; Tensile strength; Wire; Wire drawing
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2022.144041

High-strength metallic wire is a vital bearing structure used in many industrial fields. Impact loads often challenge the service safety of metal wire in engineering applications. However, few studies have been made on the dynamic mechanical behavior of metallic wires, especially for newly developed high-entropy alloy wires. By equipping split Hopkinson tension bar (SHTB) with specially designed test fixtures, we have carried out a systematic study on the dynamic deformation behavior of the heavily-drawn CoCrNi medium-entropy alloy (MEA) wire in impact tension at both room and cryogenic temperatures. We show that these millimeter-diameter MEA wires with nano-scale grains can achieve an excellent combination of impact tensile strength and ductility at 293 K and 77 K. More interestingly, we find that the strength and ductility of the MEA wire were enhanced simultaneously with decreasing temperature and increasing strain rate. Detailed microstructure characterizations and molecular dynamics simulations reveal that the increased strength and ductility at coupled high strain and low temperature resulted from the multiplication and thinning of nanoscale twins, which further caused additional strengthening and toughening mechanisms such as stack faulting net and secondary twin. This study highlights the advantage of CrCoNi MEA wire for cryogenic temperature and impact applications and provides an experimental reference for the design and evaluation of high-strength metal wires under such extreme conditions. •Two types of Hopkinson tie bar clamps are designed to obtain accurate wire dynamic stress-strain curves.•The cold-drawn wire exhibits an ultrahigh strength at cryogenic temperature and dynamic tension.•The CoCrNi wires can achieve a good combination of high strength and large engineering elongation via heat treatment.