Topic: Comparison of Microstructures and Mechanical Properties for Solid and Mesh Cobalt-Base Alloy Prototypes Fabricated by Electron Beam Melting

Speaker: Prof. Dr. Lawrence. E. Murr

　　　Materials Research & Technology Institute
　　　　　The University of Texas at Elpaso, USA

Time: 14:00-15:30, (Fri.) 11,June, 2010

Venue: Room 403, R&D building, IMR CAS

Welcome to attend!

Abstract

The microstructures and mechanical behavior of simple, as-fabricated, solid geometries (with a density of 8.4 g/cm3), as-fabricated and fabricated and annealed femoral (knee) prototypes, and reticulated mesh components (with a density of 1.5 g/cm3) all produced by additive manufacturing (AM) using electron beam melting (EBM) of Co-26Cr-6Mo-0.2C powder are examined and compared in this study. Microstructures and microstructural issues are examined by optical metallography, SEM, TEM, EDS, and XRD while mechanical properties included selective specimen tensile testing and Vickers microindentation (HV) and Rockwell C-scale (HRC) hardness measurements. Orthogonal (X-Y) melt scanning of the electron beam during AM produced unique, orthogonal and related Cr23C6 carbide (precipitate) arrays with dimensions of ~2 mm in the build plane perpendicular to the build direction, while connected carbide columns were formed in the vertical plane, parallel to the build direction, with microindentation hardnesses ranging from 4.4 GPa to 5.9 GPa; corresponding to a yield stress and UTS of 0.51 GPa and 1.45 GPa with elongations ranging from 1.9% to 5.3%. Annealing produced an equiaxed fcc grain structure with some grain boundary carbides, frequent annealing twins, and often a high density of intrinsic {111} stacking faults within the grains. The reticulated mesh strut microstructure consisted of dense carbide arrays producing a microindentation hardness of 7.7 GPa or roughly 70% higher than the fully dense components.