Preparation And Properties Of Ultra-fine TiC_0.5 Particles Reinforced Ultra-fine Grain Cu-Al Matrix Composites

Based on analysis of the limitation on ductility of copper matrix composites, the scientific and technical problems about preparation of nonstoichiometric TiCo.s reinforced copper matrix composite were studied, which was in situ formed by the decomposition of Ti2AlC in Cu-Ti2AlC system. Firstly, the reaction mechanism between Ti2AlC and Cu was studied by DSC, XRD and SEM. The formation mechanism of TiC0.5and effects on the morphology, size and distribution of TiC0.5particles were also illustrated; the optimize preparation process of the TiC0.5/Cu-Al composites was confirmed by comparing the microstructure of the composites; the phase composition of the composites and the chemical composition of the matrix were analyzed, and the microstructure of TiC0.5, matrix and interface between TiC0.5and matrix were also observed; the density, Vickers hardness, compressive properties, tensile properties and ductility of the fabricated composites were tested; the grain refinement mechanism of the matrix and the strengthening mechanism were analyzed; the hot workability of the TiC0.5/Cu-Al composites was preliminarily studied.The study results showed that:(1) A new ultra-fine TiC0.5particles reinforced ultra-fine grain Cu-Al matrix composites was fabricated by a general pathway of sintering a mixture of coarse Cu and Ti2AlC particles.(2) The initial reaction temperature between Ti2AlC and Cu is far below the melting temperature of Cu. The reaction process shows that the Al atoms of Ti2AlC diffuses into Cu matrix, and some of Cu atoms also diffuses into Ti2AlC along the diffusion path of Al atoms; with increasing sintering temperature, the diffusion of Al atoms and Cu atoms is intensified, and some TiC0.5microcrystal begins to form within the Ti2AlC particles. The TiC0.5microcrystal rapidly grows and the diffusion process finishes, when the temperature increases to the melting point of Cu.(3) The micron size Ti2AlC particles can decompose into submicron and nano size TiCo.s particles. The distribution of TiC0.5particles become more uniform with increasing Ti2AlC content, but the particle size also becomes larger. The nano size TiCo.s particles can serve as nucleuses to refine the matrix grain. The interfacial bond between TiC0.5and matrix is good, and the interface thickness is about1nm. The Al4CU9intermetallic compound will be formed, if the volume fraction of Ti2AlC in starting material exceeds52.92%.(4) The particle size of all generated TiC0.5can be reduced down to nano size by decreasing the particle size of origin Ti2AlC particles in starting materials(5) The fabricated composites are both high strength and high ductility. The average tensile strength of20Ti2AlC/Cu composite is498MPa with an elongation of10.5%. The average compressive fracture strength of40Ti2AlC/Cu sample reaches1126MPa and the average fracture strain still keep12.8%. The20Ti2AlC/Cu and30Ti2AlC/Cu samples keep undamaged even after the strain of26.7%. The improved strength of the TiC0.5/Cu-Al composites is derived from multiple strengthening effects, including fine-grain strengthening, dispersion strengthening, solid-solution strengthening and load transfer strengthening. The fine-grain strengthening makes the largest contribution to the improvement.(6) The TiCo.s/Cu-Al composites with low TiC0.5content possess a good hot workability.(7) The increase of electrical resistivity of TiC0.5/Cu-Al composites with low TiC0.5content mainly depends on the content of Al solute atoms, while the increase of electrical resistivity of TiC0.5/Cu-Al composites with higher TiC0.5content caused by both the content of Al solute atoms and the TiC0.5content.The innovations of this work:(1) The problem of interfacial bond between ceramic particle and copper matrix has been solved using TiC0.5as reinforcement.(2) The ultra-fine nonstoichiometric TiC0.5was formed by insitu reaction between larger Ti2AlC and Cu particles, which solved the problem of difficulty to obtain the nonstoichiometric TiC0.5and fine particle agglomeration caused by adding ceramic particle directly.(3) The ultra-fine microstructure Cu-Al alloy matrix was obtained by effects of TiC0.5on crystallization and the alloying effects between Al atoms and Cu matrix.