Microstructure and Plastic Instability of (ZrB2 + Al3Zr)/AA6016 Composites Prepared by Melt Reaction Method

The particle-reinforced (ZrB2 + Al3Zr)/AA6016 composites with different contents were prepared by in-situ chemical reaction of the Al-KBF4-K2ZrF6 system. With the (ZrB2 + Al3Zr) particles introduced, the composites exhibit enhanced mechanical properties and plastic instability. The ultimate tensile strength (UTS), yield strength (YS) and elongation of as-cast 6wt.% (ZrB2 + Al3Zr)/AA6016 composites reach 259 MPa, 102 MPa and 21.6%, respectively, which is significantly higher than the matrix with UTS-172 MPa, YS-70 MPa and EL -15.2%. The strain hardening rate curve shows that the presence of particles hinders the dislocation propagation process. According to the dynamical strain aging (DSA), the blocking effect of particles on dislocation motion is further strengthened with the increase of particle density, a larger span of upper and lower yield points appears. The moving range of active dislocations is reduced, which makes the time for fixed dislocations shorter. The existence of reinforcing particles indirectly affects the diffusion of solute atoms and the process of pinning dislocations during heat treatment. After T6 treatment, the type of serration was converted from (A + B) type to type B, and the serration frequency decreased with the increase in stretching rate.