Application of harmonic structure design to biomedical cocrmo alloy for improved mechanical properties

Abstract

Harmonic structure is a recently introduced concept for material microstructure design. It is essentially a bimodal microstructure in which deliberately introduced structural heterogeneity has a specific order: interconnected network of ultra-fine grained (UFG) regions, called shell area, and coarse-grained regions called core area. Such microstructural features dictate a unique set of properties to the Harmonic-structured materials. The present paper deals with the application of harmonic structure design to biomedical CoCrMo alloys for improved mechanical properties. In the present work, it has been demonstrated that full density CoCrMo alloy compacts with harmonic structure can be successfully prepared by controlled mechanical milling followed by spark plasma sintering of the pre-alloyed powders at 1323K for 3.6 ks. Sintered compacts exhibited an excellent combination of strength and ductility. Moreover, it has been also shown that the mechanical properties depend strongly on the volume fraction of the inter-connected three-dimensional network of fine-grained regions, i.e., shell volume fraction. In addition, the plastic deformation of harmonic structure CoCrMo alloy also led to -FCC to 3/4-HCP allotropic transformation. Therefore, the application of harmonic structure design leads to the new generation microstructure of biomedical CoCrMo alloys, which demonstrates outstanding mechanical properties compared to conventional materials. © 2013 The Japan Institute of Metals and Materials.