Interfacial microstructures and properties of hyper-eutectic Al–21Si / hypo-eutectic Al–7.5Si bimetallic material fabricated by liquid–liquid casting route

Abstract

Abstract. The bimetal casting process using the liquid–liquid technique was developed to produce a high-quality hyper-eutectic Al–21Si / hypo-eutectic Al–7.5Si alloy bimetal material. Microstructure and microhardness were investigated as a function of the time interval between pouring hypo-eutectic and hyper-eutectic alloys. A bimetal material was successfully fabricated using a liquid–liquid casting technique with a 10 s time interval in a permanent mould casting. A unique structure comprised of hyper-eutectic Al–21Si, hypo-eutectic Al–7.5Si and a eutectic interface of 70 µm thickness was obtained. This structure totally differs from that obtained using a higher time interval above 10 s that showed an imperfect interface bond due to the shrinkage cavity and formation of oxides. The hardness variation from the upper zone of 117.5 HV to the lower zone of 76 HV corresponded to the variation in Si and the content of other alloying elements. The proposed total solidification time control method is a promising approach for the successful fabrication of liquid–liquid bimetal material.

Recent Trends in Casting Technology of Functionally Graded Metallic Alloys

“…Mohamed Ramadan et al [99] recently explored bimetal casting using the liquid-liquid method to create a bimetal of two hyper-and hypo-eutectic aluminum alloys: Al-21 wt% Si and Al-7.5 wt% Si, respectively. The results indicated that a bimetal material was effectively produced in a permanent mold casting utilizing a liquid-liquid casting process with a time interval of 10 s. A novel structure was created with a bimetal and a eutectic interface with a thickness of 70 µm.…”

A Novel Approach of Optimum Time Interval Estimation for Al-7.5Si/Al-18Si Liquid–Liquid Bimetal Casting in Sand and Metallic Moulds

“…The experimental time interval of 10 s is less than that obtained by theoretical TST, with about 2 s for the same cast modulus. Previous work [24] reported an optimum experimental time interval of 10 s for Al-21Si/Al-7.5Si bimetal composite in a metallic mould. The optimum time interval of Al/Al bimetal casting in metallic moulding was estimated by subtracting 1-5 s from the TST value of M1, considering theoretical and experiment errors.…”

“…On the other hand, liquid-liquid methods have seen very little research published due to the requirement for two melting furnaces and two gating systems. In addition, it is essential to cautiously control the time between pouring the first metal and the second metal [24].…”

Study on bimetallic composites interface of Al/SiCp-Al matrix composites prepared by liquid-liquid compound casting

“…Liquid–liquid compound casting is a method of direct-compounding two liquid alloys through a certain casting process without coating treatment. This technique offers an effective means to simplify the preparation process of bimetallic composites without introducing heterogeneous elements [ 11 , 12 ]. Because of the good fluidity of a liquid aluminium alloy, an oxide layer can be very easily formed on its surface.…”