Elevated temperature tensile properties and thermal expansion of CNT/2009Al composites

1.5 vol.% and 4.5 vol.% carbon nanotubes reinforced 2009Al (CNT/2009Al) composites with homogeneously dispersed CNTs and refined matrix grains, were fabricated using powder metallurgy (PM) followed by 4-pass friction stir processing (FSP). Tensile properties of the composites between 293 and 573 K and the coefficient of thermal expansion (CTE) from 293 to 473 K were tested. It was indicated that load transfer mechanism still takes effect at temperatures elevated up to 573 K, thus the yield strength of the 1.5 vol.% CNT/2009Al composite at 423-573 K, was enhanced compared with the 2009Al matrix. However, for the 4.5 vol.% CNT/2009Al composite, the yield strength at 573 K was even lower than that for the matrix, due to the quicker softening of ultrafine-grained matrix. Compared with the 2009Al matrix, the CTEs of the composites were greatly reduced for the zero thermal expansion and high modulus of the CNTs and could be well predicted by the Schapery's model.