Papers by Keyword: Secondary Arm Spacing

Abstract: This study investigates the microstructure and the solidification behavior of titanium-alloyed gray irons. Thermal analysis technique was used to identify the Temperature of Liquidus Arrest (T_LA), the Temperature of Eutectic Undercooling (T_EU) and the Temperature of the Eutectic Recalescence (T_ER). It was found that the titanium addition promoted the formation of the primary austenite causing the larger difference in T_LA and T_EU. In addition, titanium encouraged the refining of eutectic mixture. The SEM showed the graphite particles were refined with increasing titanium. Fine particles of titanium-containing compound were readily observed throughout the microstructure. The hardness as high as 176 HB was achieved at 0.495%Ti addition.

Abstract: In the fragmentation theory of T. Campanella et al, the local remelting of dendrite arms is induced by the solute-rich fluid flow. Based on this theory, the effects of linear EMS intensity and solute content on CET of steel are investigated. The conclusions are as follows: The criterion for dendrite fragmentation under linear EMS is derived based on dendrite fragmentation theory by T. Campanella et al. And the criterion is verified with steel experiments. It is valid for steel under the Linear EMS. Investigation is carried out on relation between critical volume fraction of solid and solute content at the time of dendrite fragmentation (CET occurrence). It is concluded that critical volume fraction of solid is small with low EMS intensity and it decreases with the increase of solute content (C, Mn). The reason is that it causes that flow in the mushy zone becomes small which leads to CET occurrence difficult.

Abstract: The coarsening of secondary dendrite arms is discussed in terms of two different driving forces, which are the curvature effect and the temperature gradient zone melting (TGZM) effect. It is shown that the driving force due the TGZM effect can be higher than that due to the curvature effect at high temperature gradients and equal to each other at medium temperature gradients. For such high and medium temperature gradients, simple analytical models are proposed to predict the coarsening kinetics of secondary arms during solidification in a binary alloy. The prediction of the present analytical model agrees with experimental data obtained from the solidification of Fe – 1.6 wt. % Mn – 0.75 wt. % C steel.

Abstract: The scroll compressor with high cooling efficiency and lower oscillating noise can be a candidate material for a part of car air conditioner, household air conditioner and so on. When Al alloy with high strength is used for scroll compressor instead of cast iron, rotation speed can be increased by weight reduction. To design Al alloy which has enough mechanical properties to replace cast iron, the effect of alloying elements, such as Si(13-15%), Cu(4-5%), and Mg(0.5-1%) and cooling rates on the mechanical properties of squeeze cast Al alloy was studied. The influence of Sr and P modification treatment on Si morphology was also studied. Aluminum alloy over 400MPa of tensile strength and 2% elongation was developed. Al scroll samples was fabricated by squeeze casting machine(UBE 800ton) with using 2 cavity mold. Flow-3D which is a three dimensional melt flow analysis program was used to find most proper mold design and optimum process conditions for squeeze casting before making samples. Relationship between secondary dendrite arm spacing and cooling rate was simulated by Flow-3D and compared with experimental results.