Effects of Chromium Carbide Coatings on Microstructure and Thermal Conductivity of Mg/Diamond Composites Prepared by Squeeze Casting

Abstract

Magnesium matrix composites are considered a desired solution for lightweight applications. As an attractive thermal management material, diamond particle-reinforced Mg matrix (Mg/diamond) composites generally exhibit thermal conductivities lower than expected. To exploit the potential of heat conduction, a combination of Cr coating on diamond particles and squeeze casting was used to prepare Mg/diamond (Cr) composites. The thickness of the Cr coating under different coating processes (950 °C/30 min, 950 °C/60 min, 950 °C/90 min, 1000 °C/30 min, and 1050 °C/30 min) was measured by FIB-SEM to be 1.09–2.95 μm. The thermal conductivity (TC) of the Mg/diamond composites firstly increased and then decreased, while the coefficient of thermal expansion (CTE) of Mg/diamond (Cr) composite firstly decreased and then increased with the increase in Cr coating thickness. The composite exhibited the maximum TC of 202.42 W/(m·K) with a 1.20 μm Cr coating layer, while a minimum CTE of 5.82 × 10−6/K was recorded with a coating thickness of 2.50 μm. The results clearly manifest the effect of Cr layer thickness on the TC and CTE of Mg/diamond composites.

Semi-Solid Casting of AlN Reinforced Mg-Matrix Composites and their Thermophysical Properties

“…Adding 20wt.%AlN decreases the TC at room temperature by 3.5%, from 129.7 W/(m•K) to 125.1 W/(m•K) in this study. Li et al [9] have reported a similar phenomena of TC reduction in Dia/Mg composites. Even diamond with a TC of up to 2000W/(m•K) cannot improve the TC of magnesium alloys in the absence of surface treatment.…”

“…By combining these components with magnesium-based materials, composites with excellent TC and minimal CTE may be produced. Li et al [9] combined Cr-coated diamond and pure magnesium utilizing the pressure infiltration approach to produce magnesium-based composites with improved thermal properties. This Dia/Mg composite achieved TC of 202.42 W/(m•K) at room temperature with CTE of 5.82×10 -6 K -1 .…”

Tribological, mechanical and thermal response of diamond micro-particles reinforced copper matrix composites fabricated by powder metallurgy

“…Figure 1 shows a poor interfacial connection between the copper and the diamonds is indicated by the presence of large cracks at the boundaries and the majority of the diamond particles being exposed on the fracture surfaces. The literature survey implies that the use of Cr-coating can efficiently enhance the interfacial bonding between the particles and the matrix, which in turn makes it easier to densify composite materials as a whole [13]. However, the addition of higher content of diamond particles and reinforcement can make the densification more complicated because there is no suitable matrix that can fill in the spaces created by the adjacent diamond particles, there is a very low relative density when the particle concentration is exceeded.…”

Surface Coatings of Reinforcement Phases in Magnesium Matrix Composites: A Review

“…In addition to the research above, several carbon materials have also been studied. By coating TiC or Cr on diamond, the thermal conductivity of diamond/Mg composites is significantly improved [106,107]. Olszówka-Myalska et al [108] applied amorphous carbon with an irregular shape as the reinforcement and coated it with SiO 2 by the sol-gel method.…”