Semi-solid 2024 aluminum alloy billets were prepared by conventional RAP route（recrystallization and remelting）

and a cap parts were produced with the semisolid billets by thixoforging.The inhomogeneity of microstructure and composition as well as processing parameters of billet prepared were analyzed.The results show that the microstructure solidified from liquid phase is relatively minor at the center of billet

and liquid phase deposition at the flange region is major

resulting in shrinkage defects and micro-cracks.The composition segregation exhibits serious increasingly near to the flange region

and the segregation can be reduced with in the crostructure with fine grains.