Tensile Properties and Fracture Behavior of a Powder-Thixoformed 2024Al/SiCp Composite at Elevated Temperatures

Abstract

Abstract:In the present work, the tensile properties and fracture behavior of a 2024Al composite reinforced with 10 vol % SiC p and fabricated via powder thixoforming (PT) were studied at temperatures ranging from 25 • C to 300 • C with a strain rate of 0.05 s −1 , as well as the PT 2024 alloy. The results indicated that the tensile strengths of both the PT materials were all decreased with increasing the temperature, but the decrease rate of the composite was smaller than that of the 2024 alloy, and the composite exhibited higher tensile strength than that of the 2024 alloy at all of the employed testing temperatures due to the strengthening role of SiC p . Increasing temperature was beneficial for enhancing the ductility of materials, and the maximum elongation was reached at 250 • C. The elongation decrease over 250 • C was attributed to the cavity formation due to the debonding of the SiC p /Al interface and the fracturing of the matrix between SiC p . The fracture of the composite at room temperature initiated from the fracture of SiC p and the debonding of the SiC p /Al interface, but that at high temperatures was dominated by void nucleation and growth in the matrix besides the interface debonding.

Effects of T6 Treatment, Tensile Temperature, and Mass Fraction of SiC on the Mechanical Properties of SiCp/6061Al Composites

“…Atrian et al pointed out that the properties of SiC particles did not change significantly during the temperature increase, while the 6061 aluminum alloy matrix softened and the dislocations mobility increased with the increasing temperature to reduce the tensile strength of composites [21]. The phenomenon was also similar to that obtained by Li et al with SiC p /2024Al composites [22]. For direct strengthening, external stress is generally transmitted from the matrix to the reinforcement through the interface.…”

“…For direct strengthening, external stress is generally transmitted from the matrix to the reinforcement through the interface. Li et al reached this conclusion through a calculation that showed that high temperature degraded the load-transfer strengthening [22]. For indirect strengthening, dislocation strengthening is significantly dependent on the density of dislocations.…”

“…The fracture morphology is characterized by large pits and heaves when the temperature is 200 °C, as shown in Figure 13c, which indicates a brittle fracture feature and a reduced elongation. Li et al pointed out that the void nucleation in the matrix will be more extensive when the temperature increases, and cracks will initiate in, and propagate along with, the matrix [22]. Excessive softening of the matrix dominates the fracture and most particles simply separate from the matrix along with the interface.…”