The increasing demand for reducing vehicle weight in the automotive and aerospace industries has raised the need to develop improved structural aluminum-based alloys. Thus, horizontal solidification experiment with th...The increasing demand for reducing vehicle weight in the automotive and aerospace industries has raised the need to develop improved structural aluminum-based alloys. Thus, horizontal solidification experiment with the Al-7%Si-0.3%Mg（mass fraction） alloy was carried out. A water-cooled horizontal directional solidification device was developed and used. Microstructural characterization was carried out using traditional techniques of metallography, optical microscopy and SEM microscopy. The Thermo-Calc software was used to generate the solidification path of the investigated alloy with addition of 0.17% Fe（mass fraction）. The effects of the thermal parameters such as the growth rate（VL）, cooling rate（TC） and solidification local time（tSL） on the formation of the macrostructure and on the dendritic microstructure evolution were evaluated. A columnar to equiaxed transition（CET） was found for VL and TC values from 0.82 to 0.98 mm/s and from 1.71 to 2.55 ℃/s, respectively. The microstructure was characterized by the measurement of the primary and secondary dendrite arm spacings（λ1 and λ2, respectively）. Experimental laws of λ1 =f（VL, TC） and λ2 =f（tSL） were proposed. It is observed that the interdendritic region is composed of the following eutectic mixture： a（Al）＋Si＋p-Al8 Mg3 Fe Si6＋q-Mg2 Si.展开更多
As-cast samples of the Al-3wt.%Ni-lwt.%Bi alloy resulting from the horizontal directional solidification process were subjected to the micro-abrasive wear test.The effects of the solidification thermal and microstruct...As-cast samples of the Al-3wt.%Ni-lwt.%Bi alloy resulting from the horizontal directional solidification process were subjected to the micro-abrasive wear test.The effects of the solidification thermal and microstructural parameters,such as the growth and cooling rates and the cellular and primary dendritic spacings(VL and TR;λ1 and λc;respectively),were evaluated in the wear resistance of the investigated alloy.The tribological parameters analyzed were the wear volume and rate(Vw and Rw).The solidification experiments and the wear tests were carried out by means of a water-cooled horizontal directional solidification device and a rotary-fixed ball wear machine,respectively.The results show lower Vw and Rw values correspond to finer microstructures and the Vw dependence on λ1 is characterized by an experimental mathematical equation.A better distribution of Bi soft droplets and Al3Ni hard intermetallic particles is observed within the finer interdendritic region and,in consequence,the better wear resistance is achieved in as-cast samples with dendritic morphology rather than cellular morphology.A transition of wear mechanism from adhesive to abrasive is observed.展开更多
基金financial support provided by IFPA-Federal Institute of Education, Science and Technology of Pará, UFPA-Federal University of Pará, and CNPq-The Brazilian Research Council (Grants 472745/2013-1, 308784/2014-6 and 302846/2017-4)FAPESPA-Amazon Foundation of Support to Study and Research (Grants ICAAF 064/2016)CAPES-Coordination of Superior Level Staff Improvement, Brazil
文摘The increasing demand for reducing vehicle weight in the automotive and aerospace industries has raised the need to develop improved structural aluminum-based alloys. Thus, horizontal solidification experiment with the Al-7%Si-0.3%Mg（mass fraction） alloy was carried out. A water-cooled horizontal directional solidification device was developed and used. Microstructural characterization was carried out using traditional techniques of metallography, optical microscopy and SEM microscopy. The Thermo-Calc software was used to generate the solidification path of the investigated alloy with addition of 0.17% Fe（mass fraction）. The effects of the thermal parameters such as the growth rate（VL）, cooling rate（TC） and solidification local time（tSL） on the formation of the macrostructure and on the dendritic microstructure evolution were evaluated. A columnar to equiaxed transition（CET） was found for VL and TC values from 0.82 to 0.98 mm/s and from 1.71 to 2.55 ℃/s, respectively. The microstructure was characterized by the measurement of the primary and secondary dendrite arm spacings（λ1 and λ2, respectively）. Experimental laws of λ1 =f（VL, TC） and λ2 =f（tSL） were proposed. It is observed that the interdendritic region is composed of the following eutectic mixture： a（Al）＋Si＋p-Al8 Mg3 Fe Si6＋q-Mg2 Si.
基金financial support provided by IFPA-Federal Institute of Education, Science and Technology of Pará, UFPA-Federal University of Pará, and CNPq-The Brazilian Research Council (grants 302846/2017-4 and 400634/2016-3)CAPES-Coordenacao de Aperfeicoamento de Pessoal de Nível SuperiorBrasil-Finance Code 001
文摘As-cast samples of the Al-3wt.%Ni-lwt.%Bi alloy resulting from the horizontal directional solidification process were subjected to the micro-abrasive wear test.The effects of the solidification thermal and microstructural parameters,such as the growth and cooling rates and the cellular and primary dendritic spacings(VL and TR;λ1 and λc;respectively),were evaluated in the wear resistance of the investigated alloy.The tribological parameters analyzed were the wear volume and rate(Vw and Rw).The solidification experiments and the wear tests were carried out by means of a water-cooled horizontal directional solidification device and a rotary-fixed ball wear machine,respectively.The results show lower Vw and Rw values correspond to finer microstructures and the Vw dependence on λ1 is characterized by an experimental mathematical equation.A better distribution of Bi soft droplets and Al3Ni hard intermetallic particles is observed within the finer interdendritic region and,in consequence,the better wear resistance is achieved in as-cast samples with dendritic morphology rather than cellular morphology.A transition of wear mechanism from adhesive to abrasive is observed.
