Kerem Altug Guler

Fabrication of Al/Mg Bimetal Compound Casting by Lost Foam Technique and Liquid-Solid Process

Abstract In the present experimental study, bimetal aluminium/magnesium macro composites which contain magnesium core were fabricated via compound casting by lost foam casting process. AM50 Mg alloy prismatic core was placed into a cubic EPS foam pattern. Conventional process steps of lost foam casting were followed and A319 casting aluminium alloy was melted and poured. Experimental studies have shown that determination of casting temperature is very important to avoid melting of Mg alloy core. Microstructures of sectioned cast specimens were observed by light microscope and scanning electron microscope (SEM). Energy dispersive X-ray spectroscopy (EDS) analysis and Brinell hardness tests were carried out. Especially, transition zone and Al/Mg interface were in the focus of research.

A novel method for Al/SiC composite fabrication: Lost foam casting

Abstract In this paper, an innovative manufacturing approach to cast metal-matrix composite is proposed. Aluminum matrix composite production by lost foam casting has been investigated. In order to produce metal-matrix composite by lost foam casting, expanded polystyrene boards were designed as sandwich shaped and three layered. SiC particulates with 60 lm average grain size were settled between the board layers, while A6063 and A413 aluminum alloys were used as matrix materials. The effect of the matrix materials on the mechanical properties of the composite specimens was investigated and fabricated specimens were characterized using image analysis, hardness tests, scanning electron microscope and X-ray diffraction analysis. The results show that in the lost foam casting method, the hardness of the A6063 and the A413 materials specimens increases with SiC reinforcement up to 70% and 80%, respectively.

Casting Quality of Gypsum Bonded Block Investment Casting Moulds

In this study surface finish and dimensional charactersitics of castings produced with gypsum bonded block investment moulds were investigated. Commercial and laboratory made gypsum bonded investment moulds were used for investment casting mould making. To compare the casting quality of the investment powders, wax patterns for surface roughness specimens and linear dimension measurement specimens were designed and produced with special geometry. Wax trees were assembled with these patterns, cylindrical stainless steel perforated flasks were settled around the trees and gypsum bonded investment slurries were filled into flasks. Conventional tin bronze was subsequently cast into these moulds by vacuum assisted casting process. Afterwards, surface roughnesses of specimens were measured and linear dimensions of wax patterns and cast specimens were compared to determine percantage of dimensional change.

Surface Quality and Dimensional Accuracy of Gypsum Bonded Investment Flask Casting Moulds

Abstract In this study surface finish and dimensional charactersitics of castings produced with gypsum bonded block investment moulds were investigated. Commercial and laboratory made gypsum bonded investment moulds were used for investment casting mould making. To compare the casting quality of the investment powders, wax patterns for surface roughness specimens and linear dimension measurement specimens were designed and produced with special geometry. Wax trees were assembled with these patterns, cylindrical stainless steel perforated flasks were settled around the trees and gypsum bonded investment slurries were filled into flasks. Conventional tin bronze and sterling silver were subsequently cast into these moulds by vacuum assisted and vacuum pressure casting processes, respectively. Afterwards, surface roughness of specimens were measured and linear dimensions of wax patterns and cast specimens were compared to determine percentage of dimensional change.

Effects of pattern coating and vacuum assistance on porosity of aluminium lost foam castings

Lost foam casting (LFC) process has several advantages when compared to conventional sand casting techniques however formation of large amount of gaseous products during foam pattern removal increases porosity fraction of castings, especially for low melting point A1 and Mg alloys. In this study pattern coating and vacuum assistance at the time of filling were investigated and their characterizations in constant casting conditions have been determined. Green sand moulding technique was carried out for all moulds because it is necessary to obtain sound castings by using expandable polystyrene (EPS) foam patterns without refractory coating. Simple prismatic shaped patterns were prepared from cutting pieces from an EPS isolation board. A well-known A380 Al-Si-Cu casting alloy was cast at 730°C. As expected, pattern coating reduce the gas permeability and increase porosity however metal penetration into sand grains and surface roughening occurs without coating. Slight vacuum were applied to moulds with vacuum casting machine until solidification. Vacuum assistance enhanced gas removal and it has clear effect on decreasing porosity.

The Effects of Process Parameters on the Recycling Efficiency of Used Aluminium Beverage Cans (UBCs)

Abstract In this paper, the effects of process parameters on the recycling efficiency of used aluminium beverage cans (UBCs) were investigated. In the experimental studies, separated internal workshop scraps and used aluminium beverage cans are used as charge materials for melting process. Aluminium beverage cans are thin walled parts and produced with high Mg content aluminium alloys. Thus its high oxidation affinity reduces recycling efficiency of the cans. Used can pieces were pressed to obtain briquettes for charging. To increase the recycling efficiency and to optimize the process conditions, preheating, pre-charging, and fluxing were applied. The optimum parameters that provide the maximum recycling efficiency were determined. Chemical analyses and tensile tests were carried out with the resulting as cast samples.

A study of expanded polyethylene (EPE) pattern application in aluminium lost foam casting

The lost foam casting (LFC) process is a kind of casting technique based on using refractory coated polymeric foam patterns and replacing of them by liquid metal during filling. Except limited applications of other kind of foams, expanded polystyrene (EPS) is the most common pattern material of LFC process. It has been used since onset of the method. In this work, expanded polyethylene (EPE) was used as alternative pattern material and compare with EPS by aluminium castings in two different temperatures. Casting experiments were carried out with a well known aluminium alloy A380 at 720°C and 780°C. Porosity contents of the specimens were investigated and compared with density calculations and stereo microscope observations. In brief, EPE can be an alternative pattern material only in right conditions and it is not as useful as EPS. It slows down metal flow and in low casting temperatures EPE causes misrun. Also its decomposition residues contaminate moulding sand.

Investigation of Lost Foam Casted Aluminum Bimetal Microstructures

Abstract Production and applications of both ferrous and non-ferrous bimetals have been increased due to several advantages and the respective fabrication techniques and procedures are rapidly developing. Liquid metal based fabrication techniques of bimetal production can be classified in two types, i. e., liquid-solid and liquid-liquid processes. Lost foam casting technique can be successfully employed for both liquid-solid and liquid-liquid bimetal composite productions. In this study, A380 and A6063 aluminum alloys were used to produce a bimetallic structure by conventional lost foam casting with the liquid-liquid process. There are two main principles of the liquid-liquid process. Firstly, both alloys are joined in liquid phase and solidified. Secondly, crucible tilting of he metals is carried out synchronously at the same time. The Brinell hardness of the cast specimens was measured and the microstructures of the joint were investigated by light microscope and SEM. Additionally, EDX mapping analysis of the bonding zone was carried out.

Characterization of Mechanical Properties and Corrosion Behaviours of Mn and Al Bronze Castings

Abstract From ancient times to the present, copper alloys, brasses and bronzes are used for marine applications due to their high resistance to sea water. In time, numerous of copper alloys have been developed and manganese (Mn) and aluminium (Al) bronzes are the well-known members of this large family. They have superior properties and are used to produce some critical components of boats. These alloys are in competition with each other. For this reason, C86500 Mn bronze and C95800 Al bronze were evaluated in this study. Mechanical and corrosion tests were carried out on specimens which were taken from sand castings. Tensile, impact and hardness tests were applied to determine mechanical properties. Corrosion behaviour of the alloys was characterized in HCl, NaCl, and H2SO4 solutions. Additionally, microstructure observations and a definition of phases were realized. According to mechanical tests results, Al bronze has better properties than Mn bronze. Moreover, Mn bronze provides lower corrosion rates in HCl solution as Al bronze in H2SO4. Intergranular corrosion was detected in HCl solutions. Moreover, some micro shrinkage zones were seen on an Al bronze specimen after corrosion tests.

Influence of orbital shaking on microstructure and mechanical properties of A380 aluminium alloy produced by lost foam casting

Using vibration for refining microstructure and improve mechanical properties of aluminium alloys castings are in the interest of researchers for many years. Within the framework of these studies mechanical, ultrasonic and electromagnetic vibration applications were carried out. Results of these processes can be summarized as grain refining and changing the dendritic structure into globular. Accordingly increasing in density and mechanical properties were reported. In this work, orbital shaking technique was used alternatively to conventional mechanical vibration in lost foam casting (LFC) of A380 aluminium alloy. In the experiment castings, effects of shaking movement and speed during pouring were investigated. First of all orbital shaking movement has not damage LFC parts and any shape disorder was not occurred. Optical microstructure observations show that, the increase in shaking speed, decrease secondary dendrite arm spacing (SDAS) and partial dendrite arm fractures were determined at 150 rpm shaking. Density and hardness of as cast specimens were increased with shaking and rising shaking speed as well.