Toward High Strength and Large Strain Hardening Zn Alloys Via a Novel Multiscale-Heterostructure Strategy

Abstract

Zn-based alloys are regarded as one of the most promising biodegradable implants owing to their moderate degradation rate and acceptable biocompatibility. Despite some progress in addressing the strain-softening behavior of biomedical Zn-based alloys, the quest for degradable Zn-based alloys with high strength and strong strain hardening capacity remains a formidable challenge.In this work, a systematic investigation of the microstructure, phase composition, mechanical properties, and strain hardening behavior of a multiscale structured Zn-2.3Cu-0.8Mn (wt. %) alloy processed through the well-designed mechanical heat treatment processing was conducted. By manipulating the microstructure, the most promising results were obtained in the sample annealed at 330 ℃ for 1 h, which had ultimate tensile strength of ~321.4 MPa, uniform elongation of ~14.2%, and fracture elongation of ~21.1%. The high strength was primarily attributed to the coordination of hetero-deformation induced strengthening in fine/coarse grains and twins, secondary phase strengthening, and solid solution strengthening. The large strain hardening capacity was due to the bimodal structure, twinning, as well as the suppression of grain boundary sliding and phase boundary sliding. This study provides a feasible strategy for the design of Zn-based alloys with an excellent combination of high strength and large strain hardening capacity.

Keywords: Zn-based alloys, Multiscale-heterogeneous structure, Strength-ductility, Strain hardening capacity, Heterogeneous deformation-induced strengthening.