The precipitation behaviour during quenching of cast Al-7Si-0.3Mg aluminium alloy was investigated by DSC in the cooling rate range of 0.01 K/s to 3 K/s and by quenching dilatometry for higher rates. Two main precipit...The precipitation behaviour during quenching of cast Al-7Si-0.3Mg aluminium alloy was investigated by DSC in the cooling rate range of 0.01 K/s to 3 K/s and by quenching dilatometry for higher rates. Two main precipitation reactions were observed during cooling, a high temperature reaction starting almost directly with quenching from 540℃ and a low temperature reaction starting at about 400℃. Quenching with 3 K/s already significantly suppresses precipitation during quenching. Hardness after T6 ageing increases with increasing quenching rate, due to the increasing content of supersaturated solid solution. By dilatometry and hardness results the critical cooling rate can be estimated as about 60 K/s. Quenched Al-7Si-0.3Mg microstructures have been investigated by light microscopy. The microstructures consist of an aluminium-silicon eutectic structure, aluminium solid solution dendrites and precipitates inside the aluminium dendrites, depending on quenching rate.展开更多
This research work investigated the corrosion characteristics of aluminium bronze alloy in four selected aggressive media which are H2SO4, HCl, NaOH, and NaCl. Aluminium bronze alloy was produced locally via sand cast...This research work investigated the corrosion characteristics of aluminium bronze alloy in four selected aggressive media which are H2SO4, HCl, NaOH, and NaCl. Aluminium bronze alloy was produced locally via sand casting method. Copper coils and aluminium materials which constitute waste to the environment were used in producing the alloy. Test specimens were produced from the as cast alloy and immersed in H2SO4, HCl, NaOH, and NaCl environment. The concentrations of the environment were varied as 0.1 M, 0.3 M and 0.5 M. The aluminium bronze produced from sand casting has mechanical properties that are closer to the standards proposed by CDA [1]. The corrosion rate was determined by weight loss method at an interval of 3 days. It was observed that the corrosion behaviour exhibited by aluminium bronze in acidic media followed similar trends in 0.1 M, 0.3 M and 0.5 M respectively. However, the corrosion rates increases with increase in the concentration of H2SO4 and NaCl media, but the attack was more aggressive in HCl medium. The aluminium bronze samples in NaOH and H2SO4 media show gradual decolouration from its as-cast yellow golden colour to brown and dark colour respectively. NaCl environment shows high resistance to corrosion and slight decolouration effect even at increased concentration.展开更多
Virtual manufacturing based on through-process modelling becomes an evolving research area which aims at integrating diverse simulation tools to realize computer-aided design, analysis, prototyping and manufacturing. ...Virtual manufacturing based on through-process modelling becomes an evolving research area which aims at integrating diverse simulation tools to realize computer-aided design, analysis, prototyping and manufacturing. Numerical prediction of the as-cast microstructure is an initial and critical step in the whole through- process modelling chain for engineering components. A commercial software package with the capability of calculating important microstructure features for aluminium alloys is used to simulate a G-AISi7MgCu0.5 laboratory casting. The simulated microstructure, namely grain size, secondary dendrite arm spacing and diverse phase fractions are verified experimentally. Correspondence and discrepancies are reported and discussed.展开更多
The effects of various amount of Y and La on the cast structure.the fluidity,the wearability and corrosion resistance of the high manganese aluminium bronze have been investigated.The results have shown that a proper ...The effects of various amount of Y and La on the cast structure.the fluidity,the wearability and corrosion resistance of the high manganese aluminium bronze have been investigated.The results have shown that a proper content of rare earth elements is able to refine the cast structure of the alloy,and furthermore to enhance its wearability and corrosion resistance.The reasons for these phenomena have also been discussed.展开更多
The coarse blocky compounds in the as-cast 7075 aluminium alloys containing rare earth elements, neodymium, cerium or mischmetal were investigated by means of transmission electron microscope with EDX and scanning ele...The coarse blocky compounds in the as-cast 7075 aluminium alloys containing rare earth elements, neodymium, cerium or mischmetal were investigated by means of transmission electron microscope with EDX and scanning electron microscope. The blocky compounds in these alloys were identified as rare earth compounds, (Cr, Ti)2 RE (Al, X)20 (X is magnesium, copper and zinc),body-centred cubic, with 184 atoms to the unit cell , lattice parameter 1.453￣1. 458 nm, Vickers hardness 4000￣5600 MPa and calculated density 3400 kg/m3. The results show that the amount of blocky compounds in the alloys decreases with decreasing of Ti and Cr content or with increasing of cooling rate during solidification.展开更多
文摘The precipitation behaviour during quenching of cast Al-7Si-0.3Mg aluminium alloy was investigated by DSC in the cooling rate range of 0.01 K/s to 3 K/s and by quenching dilatometry for higher rates. Two main precipitation reactions were observed during cooling, a high temperature reaction starting almost directly with quenching from 540℃ and a low temperature reaction starting at about 400℃. Quenching with 3 K/s already significantly suppresses precipitation during quenching. Hardness after T6 ageing increases with increasing quenching rate, due to the increasing content of supersaturated solid solution. By dilatometry and hardness results the critical cooling rate can be estimated as about 60 K/s. Quenched Al-7Si-0.3Mg microstructures have been investigated by light microscopy. The microstructures consist of an aluminium-silicon eutectic structure, aluminium solid solution dendrites and precipitates inside the aluminium dendrites, depending on quenching rate.
文摘This research work investigated the corrosion characteristics of aluminium bronze alloy in four selected aggressive media which are H2SO4, HCl, NaOH, and NaCl. Aluminium bronze alloy was produced locally via sand casting method. Copper coils and aluminium materials which constitute waste to the environment were used in producing the alloy. Test specimens were produced from the as cast alloy and immersed in H2SO4, HCl, NaOH, and NaCl environment. The concentrations of the environment were varied as 0.1 M, 0.3 M and 0.5 M. The aluminium bronze produced from sand casting has mechanical properties that are closer to the standards proposed by CDA [1]. The corrosion rate was determined by weight loss method at an interval of 3 days. It was observed that the corrosion behaviour exhibited by aluminium bronze in acidic media followed similar trends in 0.1 M, 0.3 M and 0.5 M respectively. However, the corrosion rates increases with increase in the concentration of H2SO4 and NaCl media, but the attack was more aggressive in HCl medium. The aluminium bronze samples in NaOH and H2SO4 media show gradual decolouration from its as-cast yellow golden colour to brown and dark colour respectively. NaCl environment shows high resistance to corrosion and slight decolouration effect even at increased concentration.
基金financially supported by the Austrian Federal Government(in particular from the Bundesministerium für Verkehr,Innovation und Technologie and the Bundesministerium für Wirtschaft,Familie und Jugend)the Styrian Provincial Government,represented by sterreichische Forschungsfrderungsgesellschaft mbH+1 种基金by Steirische Wirts chaftsfrderungsgesellschaft mbH,within the research activities of the K2Competence Centre on"Integrated Research in Materials,Processing and Product Engineering"operated by the Materials Center Leoben Forschung GmbH in the framework of the Austrian COMET Competence Centre Programme
文摘Virtual manufacturing based on through-process modelling becomes an evolving research area which aims at integrating diverse simulation tools to realize computer-aided design, analysis, prototyping and manufacturing. Numerical prediction of the as-cast microstructure is an initial and critical step in the whole through- process modelling chain for engineering components. A commercial software package with the capability of calculating important microstructure features for aluminium alloys is used to simulate a G-AISi7MgCu0.5 laboratory casting. The simulated microstructure, namely grain size, secondary dendrite arm spacing and diverse phase fractions are verified experimentally. Correspondence and discrepancies are reported and discussed.
文摘The effects of various amount of Y and La on the cast structure.the fluidity,the wearability and corrosion resistance of the high manganese aluminium bronze have been investigated.The results have shown that a proper content of rare earth elements is able to refine the cast structure of the alloy,and furthermore to enhance its wearability and corrosion resistance.The reasons for these phenomena have also been discussed.
文摘The coarse blocky compounds in the as-cast 7075 aluminium alloys containing rare earth elements, neodymium, cerium or mischmetal were investigated by means of transmission electron microscope with EDX and scanning electron microscope. The blocky compounds in these alloys were identified as rare earth compounds, (Cr, Ti)2 RE (Al, X)20 (X is magnesium, copper and zinc),body-centred cubic, with 184 atoms to the unit cell , lattice parameter 1.453￣1. 458 nm, Vickers hardness 4000￣5600 MPa and calculated density 3400 kg/m3. The results show that the amount of blocky compounds in the alloys decreases with decreasing of Ti and Cr content or with increasing of cooling rate during solidification.
