The effect of copper granules on interfacial bonding and properties of the copper-graphite composite prepared by flake powder metallurgy

Microstructure and Strengthening Effect of Coated Diamond Particles on the Porous Aluminum Composites

In this work, porous Al alloy-based composites with varying Ti-coated diamond contents (0, 4, 6, 12 and 15 wt.%) were prepared, employing the powder metallurgy route and using a fixed amount (25 wt.%) of polymethylmethacrylate (PMMA) as a space holder. The effects of the varying wt.% of diamond particles on the microstructure, porosities, densities and compressive behaviors were systematically evaluated. The microstructure study revealed that the porous composites exhibited a well-defined and uniform porous structure with good interfacial bonding between the Al alloy matrix and diamond particles. The porosities ranged from 18% to 35%, with an increase in the diamond content. The maximum value of plateau stress of 31.51 MPa and an energy absorption capacity of 7.46 MJ/m³ were acquired for a composite with 12 wt.% of Ti-coated diamond content; beyond this wt.%, the properties declined. Thus, the presence of diamond particles, especially in the cell walls of porous composites, strengthened their cell walls and improved their compressive properties.

Synthesis and Workability Behavior of Cu-X wt.% TiC (x = 0, 4, 8, and 12) Powder Metallurgy Composites

In this work, copper (Cu) matrix composite reinforced with titanium carbide (TiC) was fabricated by powder metallurgy (PM) method with the varying TiC content from 0% to 12% by weight in the step of 4%. The required weight percentage of powders was milled in an indigenously developed ball milling setup. Green compacts were made using a computer-controlled hydraulic press (400 kN) and sintered in a muffle furnace at a temperature of 950°C. Scanning electron microscope (SEM) was used to analyze the distribution of TiC particles in Cu matrix in as-sintered conditions. X-ray diffraction (XRD) analysis resulted in the existence of respective phases in the produced composites. The structural characteristics such as stress, strain, dislocation density, and grain size of the milled composites were evaluated. Cold upsetting was conducted for the sintered composites at room temperature to evaluate the axial (σ z ), hoop (σ ө ), hydrostatic (σ m ), and effective (σ eff ) true stresses. These stresses were analyzed against true axial strain (ε z ). Results showed that the increase in the inclusion of weight percentage of TiC into the Cu matrix increases density, hardness, (σ z ), (σ ө ), (σ m ), (σ eff ), and stress ratio parameters such as (σ z /σ eff ), (σ θ /σ eff ), (σ m /σ eff ), and (σ z /σ θ ) of the composites.

Microstructure and Properties of Copper–Graphite Composites Fabricated by Spark Plasma Sintering Based on Two-Step Mixing

The microstructure and properties of Copper-Graphite Composites (CGC) prepared by spark plasma sintering (SPS) based on two-step mixing and wet milling were investigated. The results showed that Cu powders were rolled into Cu flakes during milling, and their size significantly decreased from 23.2 to 10.9 μm when the graphite content increased from 1.0 wt.% to 2.5 wt.%. The oxidation of Cu powder was avoided during two-step mixing and wet milling. After spark plasma sintering, the graphite powders of the composites were mainly distributed at Cu grain boundaries in granular and flake shapes. The mean size of Cu grains was 9.4 um for 1.0 wt.% graphite content and reduced slightly with the increasing of graphite content. Compared with other conventional methods, the composite prepared by two-step mixing and SPS achieved higher relative density, electrical conductivity, and micro-hardness, which, respectively, reduced from 98.78%, 89.7% IACS (International annealed copper standard), and 64 HV (Vickers-hardness) to 96.56%, 81.3% IACS, and 55 HV when the graphite content increased from 1.0 wt.% to 2.5 wt.%. As the graphite content increases, the friction coefficient and wear rate of the composite decreases. When the graphite content of CGC is 1.0 wt.%, the main wear mechanism was plastic deformation, delamination, adhesive, and fatigue wear. The adhesive and fatigue wear disappeared gradually with the increasing of graphite content.