Development of Al- TIB_2 Nanostructured Composite Using Mechanical Alloying, Spark Plasma Sintering and Hot Extrusion

摘要

Production of in situ Al- 20 wt. % TiB_2 nanocomposite powder was studied by using mechanical alloying (MA) of pure Ti, B and Al powder mixture in a planetary ball mill. A double step process was proposed to prevent the formation of undesirable phases such as AI3Ti intermetallic compound. The prepared Al- 20 wt. % TiB_2 powder was consolidated by spark plasma sintering (SPS) followed by hot extrusion with a preheating temperature of 400 °C. The structural characteristics of powder particles and consolidated samples were studied by X-ray diffractometry (XRD), scanning electron microscopy (SEM), and conventional and high resolution transmission electron microscopy (TEM). Differential scanning calorimetery (DSC) was used to study the stability of powders at high temperatures. Hardness and tensile behavior of extruded samples was also evaluated. The results showed that the prepared Al-20wt. %TiB_2 nanocomposite has good thermal stability against grain growth and particle coarsening. Extruded AI-20wt. %TiB_2 showed a hardness value of 180 VHN and yield and tensile strength of 480 and 540 MPa, respectively which are much higher than those reported for similar composites made by other processes.