Abstract:

Al-5Ti-1B （wt.%） master alloy refiner and Al-10Ce （wt.%） master alloy modifier were used to composite refine and modify ADC12 Al alloy. The phase structures， microstructures， distribution characteristics of the second phases， and interfacial bonding characteristics of the Al alloy were analyzed by X-ray diffraction （XRD）， optical microscopy （OM）， scanning electron microscopy （SEM）， and transmission electron microscopy （TEM）. The tensile properties and Brinell hardness of the Al alloy were also tested， and the correlation between microstructures and mechanical properties was established. The results showed that the refinement effect of α-Al matrix of ADC12 Al alloy after composite refinement and modification was remarkable， and the eutectic Si transformed from rough long needles to fine round short rods. After adding 0.75%AlTiB-0.75%Ce， the secondary dendrite arm spacing was reduced to11.4 μm， CeCu_0.5Si_1.5 phase was dispersed in the matrix and CeCu_0.5Si_1.5 rare earth phase was well boned with Mn_4.6Fe_0.4Si₃ Si-rich phase at the interface. The tensile strength， elongation， and Brinell hardness of the Al alloy are 272.7 MPa， 3.1%， and 87.7 HB， respectively， which were increased by 79.2%， 287.5%， and 11.2% compared with as-received Al alloy. The comprehensive mechanical properties are applicable for die-casting requirements that need high-strength， heat treatment-free cast aluminum alloys， such as for manufacturing automotive engine parts， transmission casings， and similar components.

Key words: metallic materials, ADC12 Al alloy, composite refinement and modification, microstructure, mechanical property