Mechanical Phase Identification at an SiC/Ti-6Al-4V Active-Braze Interface by k-Medoids Clustering of Nanoindentation Arrays

Author(s):

Brady G. Butler, Efraín Hernández-Rivera, S. Gary Hirsch, Daniel O. Lewis, Trevor R. Hastings, and Michael T. Hurst

Abstract:

Spatially resolving mechanical properties across dissimilar-material interfaces remains challenging because microstructural features can approach the characteristic sampling volume of local mechanical measurements. Here, high-density nanoindentation was combined with microstructural characterization and spatial registration to examine a SiC/Ti-6Al-4V joint produced using an Ag-Cu-In-Ti active braze. Reference indentation measurements established the mechanical response of the SiC and Ti-6Al-4V end members, while 10- and 20-mN NanoBlitz arrays mapped mechanical variations across the interface. K-medoids clustering of hardness, modulus, and surface-height data was used to identify mechanically similar populations without incorporating lateral position; k-means provided an independent comparison. The mechanical maps reproduced the coarse architecture of the joint and identified distinct responses within the approximately 100-μm braze interlayer. However, narrow reaction layers, submicrometer constituents, and pore-affected measurements could not be interpreted as independent phases reliably. K-medoids provided experimentally traceable cluster representatives and reduced sensitivity to extreme measurements, although both algorithms produced similar results for well-separated populations. These results demonstrate that spatial resolution, sampling density, and correlative characterization ultimately govern mechanically based phase identification more strongly than the choice of clustering algorithm.