Microstructure and mechanical properties of <i>in-situ</i> synthesized TiB₂/Al-4.5Cu composites

Abstract

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.

Keywords

• aluminum matrix composite
• heat treatment
• microstructure
• mechanical property
• dislo-cation