中文摘要：

The high strength 7xxx series aluminium alloys are usually difficult to be prepared as semi-solid feedstock,because some dispersoid particles(soluble only in liquid) could pin at grain and subgrain boundary to make the alloy difficultly recrystallise.In this work,a novel multistep reheating regime is developed for recrystallisation and partial melting(RAP) route to prepare fine spheroidal microstructure of semi-solid AleZne MgeCu alloy.After reheating to 665℃,holding for 4 min and subsequent isothermally holding at 620℃ with total heating time of 15 min,fine spheroidal microstructures with grain size of w40 mm were prepared without remained unrecrystallised grains and directionality,which are much finer than the conventionally obtained microstructures(w100 mm).

英文摘要：

The high strength 7xxx series aluminium alloys are usually difficult to be prepared as semi-solid feedstock, because some dispersoid particles （soluble only in liquid） could pin at grain and subgrain boundary to make the alloy difficultly recrystallise. In this work, a novel multistep reheating regime is developed for recrystallisation and partial melting （RAP） route to prepare fine spheroidal microstructure of semi-solid AI-Zn- Mg-Cu alloy. After reheating to 665 ℃, holding for 4 min and subsequent isothermally holding at 620 ℃ with total heating time of 15 min, fine spheroidal microstructures with grain size of-40 μm were prepared without remained unrecrystallised grains and directionality, which are much finer than the conventionally obtained microstructures （-100 μm）.