Effect of powder microstructure on the thermal and mechanical properties of hot extruded Al-CNT composite

Abstract

To understand the effects of microstructure of powders on resultant thermal and mechanical properties of Al-CNT composite, spherical and flake Al-CNT powders are fabricated by chemical vapor deposition and ball milling. Results showed that the spherical composite powder and its extruded sample feature with coarse grains and integrated CNTs, which imparts excellent thermal conductivity, the maximum of 246.6 W m−1 K−1 (400 ℃) are obtained. However, CNTs are found agglomerating in the grain boundaries of the Al matrix, leading to poor interfacial bonding and deteriorated mechanical properties. Compared to the spherical powders, the ball-milled flake Al-CNT powders have much finer grain structures, as well as more uniformly distributed CNTs which bond better with the Al matrix. After extrusion, their ultimate strengths are significantly improved and CTEs are further reduced, the maximum ultimate strengths of 186.2 MPa and minimum CTEs of 25 × 10−6 K−1 (400 ℃) are achieved. Nevertheless, the CNTs tend to be broken in the ball milling which unfortunately damages the thermal conductivity.