Celal Cingi

Effect of Heat Treatment on Thermal Conductivity of Aluminum Die Casting Alloys

Thermal conductivity is an important property when high heat dissipation is a requirement during the use of the cast component. This study was carried out to study the effect of heat treatment on thermal conductivity of three common aluminum die casting alloys. Measurement of thermal conductivity was done by the Hot Disk method. A substantial increase in thermal conductivity was measured as a result of heat treatment. Microstructural changes due to heat treatment was examined by optical and scanning electron microscopy.

Cast Bonding of Cast Irons to Ferritic Stainless Steel

Composite metal products consisting of two different alloys can be prepared by a few methods. Cast bonding is one of these methods. The bond between the two materials forms primarily in the solid state by diffusion, after casting of a cladding alloy on to the preheated surface of a substrate. In this work, a ferritic stainless steel was used as the substrate, and, gray iron or nodular iron as the cast alloy. It was found that these two alloys can be successfully joined, and under specific casting parameters, a very strong bond develops between the two alloys. Bond strength was found to be greater than that of gray iron. Microstructural zones on both sides of the bond were studied. It was found that diffusion of chromium into iron and diffusion of carbon into steel is significant in bonding. Chemical composition changes due to diffusion was studied by EDS. Fe-Cr-Mn carbides were formed at the bond during the casting. These carbides were largely eliminated by a subsequent high temperature heat treatment.

Experimental studies on equivalent thermal properties of particle-reinforced flexible mould materials

The investment casting process uses wax patterns which may be produced using the soft tooling process where the common flexible (polymer) mould materials used are polyurethane rubber, silicone rubber, etc. of a typical kind. However, due to poor thermal conductivity of these materials, solidification time of (wax) patterns takes longer leading to reduced rapidity of the process to a great extent. This problem may be overcome by increasing thermal conductivity of mould material that can be achieved either by molecular orientation of polymer itself or by addition of conductive fillers into polymer. The method of controlled addition of thermal conductive (particulate) fillers into mould material may be adopted by realizing it as the simplest and easiest to implement technique in industry. In this article, an experimental study has been carried out to find the effects on equivalent thermal properties of flexible mould materials reinforced with conductive filler particles. Two different types of particles (aluminium and graphite) with different morphological characteristics are considered as fillers. The measurement of thermal properties is carried out by a transient plane heat source technique. As much as 10-fold increases in thermal conductivity and thermal diffusivity values of mould materials reinforced with conductive fillers are found. In explaining the experimental results by several empirical/semiempirical models, it is observed that the Lewis–Nielsen model provides a good estimation, while the Agari–Uno model (fitted with experimental data) shows better agreement than other models.