Double compound modification was carried out for hypereutectic Al-24Si alloy. The experiment showed that double modification with phosphorus and rare earth can fine the microstructure of alloy. The complex modifications of phosphorus and rare earth make the coarse block primary silicon obviously refined and the large needle eutectic silicon modified to the fine fibrous or lamella ones. The alloys with the additions of 0.10% P(phosphorus) and 0.90% RE(rare earth) have the optimal microstructure and the highest mechanical properties. Compared with the unmodified alloy, the primary silicon of alloys can be refined from 93.5μm to 24.1μm. The tensile strength is improved from 248MPa to 305MPa and the elongation is improved from 0.31% to 0.47%. Mechanism of double compound modification with phosphorus and rare earth is discussed as well.
Double compound modification was carried out for hypereutectic Al-24Si alloy. The experiment showed that double modification with phosphorus and rare earth can fine the structure of alloy. The complex modifications of phosphorus and rare earth make the coarse block primary silicon obviously refined and the large needle eutectic silicon modified to the fine fibrous or lamella ones. Phosphorus mainly refines the primary silicon. Rare earth can well refine the primary and eutectic silicon, but its modification effect on the eutectic silicon is more obvious. The alloys with the additions of 0.10% phosphorus and 0.9% rare earth have the optimal microstructure. Compared with the unmodified alloy, the primary silicon of alloys can be refined from 93.5 μm to 24.1 μm and the eutectic silicon can be refined from 8.5 μm to 5.3 μm. Mechanism of double compound modification with phosphorus and rare earth is discussed as well.
Two kinds of ZL108 alloys containing titanium are produced with electrolytic low-titanium aluminum alloy (named as ZL108D) and pure aluminum as well as Al-Ti master alloy (named as ZL108R) respectively. The influence of different titanium alloying methods on the microstructure and wear behavior is investigated. The result shows that it is an effective for grain refining of ZL108 alloy by adding titanium to the melt before casting. Addition of titanium can improve the wear resistance of ZL108 alloy, while ZL108D is superior to ZL108R. It is attributed to the addition with electrolytic low-titanium aluminum alloy results in better grain refinement.
Adopting quartz plate filter of 20 mesh to filter the ZL102 alloy compounded by Al-30Si coarse alloy produced by electric warming, the Fe content in the alloy is reduced to 0.43% from 1.14%, the big massive and petaloid Fe phase becomes fine block-like. The tensile strength and elongation of the alloy arrive at 182MPa and 4.3% respectively, which increased by 38% and 290% separately compared with the alloy without filtration. The mechanical property of this alloy has been close to the alloy compounded by pure Al and it can fully meet the demand of commercial production.
The influences of RE and P complex modification on microstructure and impact toughness of hypereutectic Al-24Si alloy are investigated. The result shows that the coarse block primary silicon is refined obviously and its edges and angles are blunted under the influences of the complex modification of RE and P. The large needle eutectic silicon is modified to the short-rod or particle ones also. The alloys have the finest microstructure and highest impact toughness when adding about 0.10% P and 0.9% RE into alloys. Compared with the unmodified alloy, the average size of primary silicon in the modified alloys refined from 93.5μm to 24.1μm and the impact toughness of alloys increases to 11.0062J/cm2 from 7.3572J/cm2. The excellent impact toughness of alloys can be attributed to the increase of initiation energy and expand energy of the cracks caused by the refinement of primary silicon and eutectic silicon after complex modified with P and RE.
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