Livarski vestnik 58 / 2011 Nr. 3
Ajay Likhite, D.R. Peshwe, S.U. Pathak
MICROSTRUCTURAL CHARACTERIZATION OF AUSTEMPERED INOCULATED LOW CARBON EQUIVALENT CAST IRONS
Jožef MEDVED, Stanislav KORES, Maja VONČINA, Primož MRVAR
THERMODYNAMIC ANALYSES OF AL-SI-CE ALLOYS
Boris Čuk
IDENTIFICATION OF DEFECTS UNDER THE SURFACE OF THIN-WALLED CASTINGS OF GREY CAST IRON
Ajay Likhite, D.R. Peshwe, S.U. Pathak
Microstructural Characterization of Austempered Inoculated Low Carbon Equivalent Cast Irons
Abstract
In the present investigation, the response of inoculated low carbon equivalent irons (Carbon equivalents in the range of 2.6 – 3.21) to austempering heat treatment was investigated. The austempering was carried out at 250 0C and 350 0C for 1 hour, 2 hours and 3 hours. It was observed that the austempering treatment produces ausferritic microstructure similar to that present in ADI. An austempering treatment of 1 hour duration was found to be adequate to prevent the formation of martensite and austempering for 3 hours did not result into the disintegration of carbon stabilized austenite.
Jožef MEDVED, Stanislav KORES, Maja VONČINA, Primož MRVAR
Thermodynamic analyses of Al-Si-Ce alloys
Abstract
Paper presents the influence of Ce addition on the hypoeutectic AlSi10Mg alloy, eutectic AlSi12 alloy and hypereutectic AlSi17 alloy. Solidification was investigated using simple thermal analysis, differential scanning calorimetry, optical microscopy and scanning electron microscopy. The purpose is to study the variations that occur at the solidification and precipitation with different Ce additions and the influence on the primary silicon phase and eutectic silicon. At commercial AlSi10Mg alloy the Ce in range of 0.01, 0.02, 0.05 and 0.1 % Ce (mass fraction ) was added. At pure binary eutectic and hypereutectic Al-Si alloy the Ce in amount of 1 % was added. The commercial alloy AlSi17CuMg with different additions of Ce was also investigated.
The results show that Ce has different influence on different types of Al-Si alloys. Ce in hypoeutectic alloy decreases precipitation energy and shifts the temperature of precipitation to lower temperature. Temperature of eutectic solidification (αAl+Mg2Si) decreases with increasing Ce addition in AlSi10Mg alloy. With the optimal Ce addition the eutectic temperature increases and the eutectic recalescence decreases. The solidus temperature also decreases with the increasing Ce addition. At hypereutectic AlSi17 liquidus temperature of the alloy decreased with increased cerium content and at eutectic AlSi12 alloy liquidus temperature increased with Ce addition. Simultaneous refinement of both, the primary and the eutectic silicon, was achieved with cerium additions.
Key words: Al-Si alloys, cerium, silicon refinement, modification, thermodynamic, thermal analysis
The results show that Ce has different influence on different types of Al-Si alloys. Ce in hypoeutectic alloy decreases precipitation energy and shifts the temperature of precipitation to lower temperature. Temperature of eutectic solidification (αAl+Mg2Si) decreases with increasing Ce addition in AlSi10Mg alloy. With the optimal Ce addition the eutectic temperature increases and the eutectic recalescence decreases. The solidus temperature also decreases with the increasing Ce addition. At hypereutectic AlSi17 liquidus temperature of the alloy decreased with increased cerium content and at eutectic AlSi12 alloy liquidus temperature increased with Ce addition. Simultaneous refinement of both, the primary and the eutectic silicon, was achieved with cerium additions.
Key words: Al-Si alloys, cerium, silicon refinement, modification, thermodynamic, thermal analysis
Identification of defects under the surface of thin-walled castings of grey cast iron
Abstract
Non-metallic inclusions appear under the surface of castings that were cast into green-sand moulds. Defects could be of slag or sand origin. The performed research revealed reasons of formation of under-surface inclusions that did not become visible until the machining. Inclusions were examined with electron microscope and EDS analyzer. Silicon was the prevailing element in inclusions which indicated that origin of inclusions was quartz grains of moulding sand. Degree of mixing in mixer was checked and based on data from references it was confirmed that sand was well mixed. The under-surface defects had their origin mainly in moulding sand containing high fraction of <0.09 mm grains and of elutriated matter. Fraction of rejected castings can be reduced with suitable management of the sand conditioning system to keep amount of <0.09 mm grains and of elutriated matter at a suitably low level.
Key words: inclusions, rejection, elutriated matter, fine fractions
Key words: inclusions, rejection, elutriated matter, fine fractions