Cooling slope casting and thixoforming of A356 and A380 aluminium alloys

In this study, the alloys (A356 & A380) were poured from the inclined copper tube with the angles of 60⁰ & 30⁰, length of 650mm and diameter of 50mm at a pouring temperatures of 635 ⁰C (A356) & 615 ⁰C (A380). The pouring was carried out on an inclined tube without vibration through cast iron die. Low superheat casting (LSC) technique was used for ingot fabrication in thixoforging process. LSC can be summarized; pouring of molten metal at a temperature very close to liquidus followed by rapid solidification. Low heat input combined with sudden cooling suppresses dendritic growth and conventional casting structure converts into more spherical structure. The billets that were produced by aforementioned procedure, were reheated between 20-80 min at 595 ⁰C (for A356) & 575 ⁰C (for A380) which 20 ⁰C below the melting temperature of the alloy. Reheated samples were formed with semi-solid forging at a rate of 50% deformation in an open die. The specimens formed by semi-solid forging were compared with as-cast and quenched specimens via optical microscope and Brinell hardness measurements in terms of microstructure and hardness properties, respectively.