Effect of Pouring Temperature and Melt Treatment on Microstructure of Lost Foam Casting of AL-Si LM6 Alloy

Abstract

This paper presents the experimental investigation conducted on Al-Si cast alloy (LM6) cast using lost foam process. The main objective of the research is to investigate the effect of pouring temperature, section thickness and melt treatment on the microstructure of the lost foam casting of Al-Si alloy. Step pattern with five different sections was prepared from 20 kg/m³ density foam and poured at five different temperatures; 700, 720, 740, 760, and 780 with and without the addition of AlTiB as grain refiner. Analysis on microstructure, eutectic silicon spacing and porosity percentage were conducted to determine the effect of both parameters. The results show that pouring temperature has significant influence on the quality as well as microstructure of the lost foam casting of LM6 Al-Si alloy. Lower pouring temperature was found to produce finer microstructure casting. However, the addition of AlTiB as grain refiner did not affect the produced castings significantly whether in terms casting quality or microstructure.

Effect of Lanthanum Addition on Microstructure and Hardness as Cooling Rate Function of ADC12 Eutectic Cast Alloy

“…A hardness measurement was conducted by using a Vickers hardness tester. [4]. With La addition showed the significant effect on Si with higher thickness (lower solidification rate) the Si particles decrease and showed very irregular, smaller, longitudinal, sharp-edged structures and a refined Si morphology comparing to base alloy.…”

“…Also, it modifies primary and eutectic silicon and decreases the size of them. Segregation between dendrites and grain boundaries decreases with increasing cooling rate [4,5]. In addition to heat treatment and alloying elements, higher cooling rates have strongly affected the mechanical properties and microstructure of near eutectic Al-Si [6].…”

“…For a long time, alterations in the growth of eutectic silicon by a large increase in twin density were used to explain eutectic modification, but more recent studies have shown that modification changes the nucleation frequency and dynamics of eutectic grains with associated effects on the growth rate [2,3]. Cooling rate is one of the most important variables which affects microstructure and mechanical properties of cast alloys [4]. High cooling rate decreases grain size, shrinkage porosity, and causes more uniform distribution of porosity.…”

Effect of Elements Cerium and Lanthanum on Eutectic Solidification of Al-Si-Cu near Eutectic Cast Alloy

“…Various additives are usually used to modify industrial alloys. Modified Al-Si alloys give better mechanical properties than unmodified alloys [5,6] Rare earth elements such as La (Lanthanum), Ce(Cerium), Y(Yttrium), and MM (Mish metal) were reported to act as an effective modifier. Rare earth will modify Si phase from acicular needles to fibrous one and is carried out to enhance the tensile properties.…”

Properties of Pressurized Lost Foam Casting of Al-11Si Alloy

“…Lost foam casting is a process used to produce complex metal parts. Although this technology has several advantages compared to conventional casting methods, it suffers from some inherent disadvantages, including coating penetration, surface roughness, defects and porosities [1][2][3]. In this method patterns usually made of expanded polystyrene, attached to a gating system and then a thin layer of refractory coating material is applied to the entire assembly.…”