Temperature-assisted microstructure development for TiB2 reinforced Cu matrix composite

Abstract

The current research demonstrates the fabrication and characterization of TiB2-reinforced (10%) Cu matrix composite through a powder metallurgy route. The composites have been prepared by hot compaction (200 °C and 500 °C) of Cu and TiB2 powders subsequent to mechanical milling in a high-energy planetary mill. The influence of temperature on the microstructure, hardness, and mechanical properties of the composites was investigated. The development of clean and well-connected interfaces between matrix and reinforcement is revealed by scanning electron microscopy (SEM). X-ray diffraction (XRD) revealed the absence of intermetallic compounds during the entire tenure of the ball milling and consolidation process. Differential scanning calorimetry (DSC) analysis displayed the possibility of oxide formation with the gases trapped inside the pores of the compacts that could not be ignored. The kinetics of the formation of Cu2O phases with associated activation energies at various temperatures were calculated using Johnson-Mehl-Avramani (JMA) equation. The values of activation energy (Q) were 405.14, 573.74, and 705.69 (KJ mol−1) for sintering at 500 °C, 200 °C, and RT, respectively. This indicates the formation of endothermic peaks at a lower temperature for samples with higher consolidation temperatures. A uniform distribution of hardness on the cross-section ensured proper load spread and an accurate selection of the H (height)/D (diameter) ratio during compaction. Increasing hardness with higher consolidation temperature might sound aberrated from the traditional understanding of softening with temperature through grain growth. A hardness value of 158.5 Hv at a higher consolidation temperature (500 °C) achieved through a reduction of porosity by removing entrapped gases with temperature outweighs the softening effect.