We　investigated　the　microstructure　evolution　of　a　6　wt%　TiB2-reinforced　Al-Zn-Mg-Cu-Zr　composite　subjected　to　hot　compression　at　temperatures　within　the　range　370　degrees　C-490　degrees　C,　at　strain　rates　between　0.001　s-1　and　10　s-1.　The　microstructure　evolution　was　characterized　by　electron　backscatter　diffraction　and　transmission　electron　microscopy.　Dynamic　recovery　and　dynamic　recrystallization　mechanisms　were　analyzed,　with　a　focus　on　nucleation　at　original　grain　boundaries　and　TiB2　particles.　The　results　show　that　recovery　is　the　main　dynamic　softening　mechanism　due　to　the　high　dislocation　mobility　in　the　Al　matrix.　However,　low　temperature　and　high　strain　rate　results　in　a　large　number　of　small　recrystallized　grains,　whereas　high　temperature　and　low　strain　rate　results　in　a　few　large　recrystallized　grains.　Dynamic　recrystallization　is　mainly　attributed　to　particle-stimulated　nucleation　occurring　near　TiB2　particles/clusters,　especially　TiB2　particles/clusters　at　grain　boundaries.　Relations　between　the　observed　dynamic　recrystallization　and　the　Zener-Hollomon　parameter　are　discussed.