The Evolution of Interfacial Microstructure and Fracture Behavior of Short Carbon Fiber Reinforced 2024 Al Composites at High Temperature

Abstract

The short carbon fiber reinforced 2024 Al composites were fabricated through powder metallurgy. The effect of short carbon fiber content on the interfacial microstructure and fracture behavior of the composites at different temperatures were investigated. The results showed that the dislocation accumulation was formed in the aluminum matrix due to the thermal expansion mismatch between carbon fiber and aluminum matrix. With the testing temperature increasing, the size of interfacial product Al4C3 and precipitates Al2Cu became larger, and the segregation of Al2Cu was found coarsening around Al4C3. The addition of short carbon fiber improved the hardness and modulus of the aluminum matrix in the vicinity of the interface between carbon fiber and aluminum matrix. Compared to the matrix 2024 Al, the yield strength and ultimate tensile strength of the composites first increased and then decreased with increasing short carbon fiber content at room temperature 423 Kand 523 K. The fracture surface of the composites at room temperature was characterized by shear failure of fiber, while the interface debonding and fiber pulled-out became predominant fracture morphologies for the fracture surface at increased temperatures.

The Role of Al4C3 Morphology in Tensile Properties of Carbon Fiber Reinforced 2024 Aluminum Alloy during Thermal Exposure

“…As shown in Figure 2, SCFs are dispersed uniformly in the 2024 Al matrix with no obvious clustering being observed. Similar results were obtained in our previous research in SCFs/2024 Al and SCFs/7075 Al [20,25]. In the transverse section, the shape of carbon fiber is mostly round.…”

“…increased the hardness from HV 92 to HV 113, enhanced by 21.5%. Because the inde tion would cover SCF in SCFs/2024 Al SCF can enhance the hardness and modulus of nearby matrix [20]. Whatever the 2024 Al and SCFs/2024 Al, HV is in a decreasing dency.…”

“…The addition of SCFs increased the hardness from HV 120 to HV 140, enhanced by 16.7%, when the thermal exposure time is 0 h. When the thermal exposure time was more than 100 h, the addition of SCFs increased the hardness from HV 92 to HV 113, enhanced by 21.5%. Because the indentation would cover SCF in SCFs/2024 Al SCF can enhance the hardness and modulus of the nearby matrix [20]. Whatever the 2024 Al and SCFs/2024 Al, HV is in a decreasing tendency.…”

“…Compared with the matrix strength of 300 MPa, it increased by 40%. Zhang et al [20] found that the highest tensile strength is obtained when the volume fraction of carbon fiber in the matrix is 4 vol.%, which is 4.6% higher than that of 2024 Al. The addition of MPCF carbon fiber was beneficial to improve the tensile strength of the as-sintered 2024 Al composites, which increased from 293 MPa to 406 MPa [21].…”

“…The addition of carbon fiber can not only improve the performance of aluminum alloy materials at room temperature but also at high temperatures. The addition of 4 vol.% carbon fiber increases the tensile strength of 2024 Al by 13.7% and 18.3% when the test temperature is 423 K and 523 K, respectively [20]. For 7075 Al, the addition of 12 vol.% carbon fiber increases the tensile strength by 15.6% and 16.5% at 150 and 200 • C, respectively [25].…”