原位自生TiB 2 /Al-4.5Cu复合材料微观组织和力学性能

Various contents (0%, 2%, 5% and 8%,mass fraction,the same below) of TiB₂/Al-4.5Cu composites were prepared by mixed salt reaction method. After T6 heat treatment, XRD, ICP, OM, SEM, EDS and tensile test at room temperature were adopted to observe microstructure and assess mechanical properties of the composites. XRD and ICP tests confirm that the alloys contained only α-Al, Al₂Cu and TiB₂,Al₃Ti and Al₂B phases are not found.OM and SEM observations show that the average grain size of α-Al in the matrix material is 167.5 μm, while is 110.4,87.2,75.2 μm in 2%, 5%, and 8% TiB₂/Al-4.5Cu, respectively. TEM observation indicates that the TiB₂ particles are quadrate and hexagonal structure dispersed in the grain boundary chiefly. Room-temperature tensile experiments show that with the increasing of TiB₂ content, the mechanical properties of TiB₂/Al-4.5Cu composites are improved gradually. Especially,for the composite with TiB₂ mass fraction of 8%, the yield strength(YS), ultimate tensile strength(UTS),elastic modulus and microhardness are 356 MPa, 416 MPa, 92.5 GPa and 96.5HV, separately. However,the elongation(δ) decreases from 10.3% to 4.3%. Analysis suggests the enhancement of load transfer, fine crystal and dislocation proliferation are all the factors that greatly improve the mechanical properties of TiB₂/Al-4.5Cu composites, in especial, the dislocation cell and loop distributed around TiB₂ particles play a decisive role in enhancing the strength.