علي خيرابي

The upcoming research has been carried out to better understand the mechanisms of the Ablation Casting in Al alloys. The following goals were intended in the current study: 1- Explaining the mechanism of air gap formation and its related point in T-t curves. 2- Introducing the DWS method as a new approach in Ablation casting with sodium silicate binder instead of Ablation water dissolvement binder makes it possible to spray water on the solidifying metal’s free surface directly. 3- Determining the effect of the freezing range in Al alloys solidification within the Ablation casting. The thermal analysis of A356 and measurement of the displacement between cast and mold reveals the beginning point of air-gap formation id after the Dendrites Coherence point (DCP). DWS method uses simple water spray instead of expensive water jet system and carries out without a water-soluble binder. The mentioned method is cheaper and has less water waste compared to Original Ablation casting (ABL). Two commercial alloys, A356 (hypoeutectic) and A413 (near eutectic), were cast by DWS and conventional CO2 sand casting. The result of the tensile test for A356 showed an increase in Ultimate tensile strength from 126 MPa to 193 MPa and the elongation percentage from 2.8% to 11.5%. For A413, the same varied from 139 MPa to 159 MPa and from 1.0% to 5%, respectively. This enhancement was because of higher cooling rates that refine the α-Al dendritic phase size, subsequent phases (eutectic), and Microshrinkage size and percentage. Due to the better results of the A356 alloy, the effect of the special binder was eva‎luated by comparison between ABL and DWS methods on this alloy. The ultimate tensile strength in ABL increased to 218 MPa, and the elongation increase shifted to 19%. The decrement in α-Al dendrites secondary arm spacing in ABL was 75% compared with CSC and 50% with DWS. The main reason for the better response of mushy solidifying alloys is the interdendritic Coalescence mechanism, which has created a better matrix of α-Al phase under effect of higher cooling rates. Due to the intense increase in the cooling rate within the ablation castings, the presence of the double-diffusive convection effect in a reduction in the SDAS size in mushy alloys was pointed out.

ريخته گري دوشابي , آلياژ آلومينيم , دامنه انجمادي , شبيه سازي , آناليز حرارتي , استحكام كششي , ريزساختار

Ablation Casting. , Al alloy , Freezing range , Simulation , Thermal Analysis , Tensile Strength , Microstructure

Ali Kheirabi

Seyed Mohammad Ali Boutorabi and Mehdi Divandari