A new measure to enhance the heat-resistant (4TiC + 5AlN)/Al composite by multi-scale Fe/Mn enrichment effect

Developing high-strength Al-based alloys that can operate at 250 degrees C and above remains a challenge. In this study, a heat-resistant and high-strength (4TiC + 5AlN)/Al-Fe-Mn composite is designed using the li-quid-solid reaction and hot extrusion. The strengthening phases, including sub-micron TiC, micron Al3(Fe, Mn), nano-sized AlN, and nano-sized Al3(Fe, Mn), in which the in-situ AlN particles are distributed in the matrix as networks, exhibit an attractive strengthening effect. Based on the results of electron backscatter diffraction, the extruded (4TiC + 5AlN)/Al-Fe-Mn composite prefers to form fiber texture in the longitudinal and cross-section: < 111 >Al//ED. And the average grain size of (4TiC + 5AlN)/Al-0.3Fe-0.1Mn composite is 0.69 mu m. The ultimate tensile strength of the (4TiC + 5AlN)/Al-Fe-Mn composite is as high as 215 MPa at 350 degrees C. And the high-temperature elongation of the (4TiC + 5AlN)/Al-Fe-Mn composite is maintained while increasing the high-temperature strength. The improved performance of the (4TiC + 5AlN)/All-Fe-Mn is attributed to the synergistic effect of the multi-scale Al3(Fe, Mn) phases and particles. Furthermore, the formed micrometer Al3(Fe, Mn) phases are used to regulate the distribution of the TiC and AlN particles. The nano-Al3(Fe, Mn) dispersoids that precipitated during the homogenization can enhance the high-tem-perature deformation resistance of the matrix. In particular, the Fe and Mn atoms tend to aggregate at the TiC/Al interface, effectively modifying the interfaces between ex-situ TiC particles and the Al matrix. The modified interfaces of TiC/Al are beneficial to load transfer strengthening. The strengthening mechanisms of the (4TiC + 5AlN)/Al-Fe-Mn composite have been analyzed in detail, and the main strength-increasing mechanisms are calculated from the microstructural data. This work may provide an important approach to preparing heat-resistant Al matrix composites with strength-ductility matching. (c) 2023 Elsevier B.V. All rights reserved.