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In this study, the effects of reinforcement volume ratios (RVR) on composite structure and thermal conductivity were examined in Al-MgO reinforced metal matrix composites (MMCs) of 5%, 10% and 15% RVR produced by melt stirring. In the production of composites, EN AW 1050A aluminum alloy was used as the matrix material and MgO powders with particle size of -105 µm were used as the reinforcement material. For every composite specimen was produced at 500 rev/min stirring speed, at 750 °C liquid matrix temperature and 4 minutes stirring time. Composite samples were cooled under normal atmosphere. Then, microstructures of the samples were determined and evaluated by using Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) analysis. In general, it was observed that the reinforcement exhibited a homogeneous distribution. Furthermore, it was determined that the increase in the RVR increased porosity. From the Scanning Electron Microscope images, a thermal Ansys model was generated to determine effective thermal conductivity. Effective thermal conductivity of Al-MgO composites increased with the decrease in reinforcement volume ratio.

Today, the usage area of metal matrix and ceramic reinforced composites is increasing and researches in this field are increasing. However, majority of the studies conducted are constituted of studies on investigation of mechanical features of composites. One of the reasons why composite materials are preferred is because these materials have improved thermal property. With this experimental study, it is aimed to contribute to the literature in the area of investigating features of thermal properties. In this study, composite materials were produced at 500 °C, 550 °C and 600 °C sintering temperatures by adding 4%, 8% and 16% B4C to Al 1070 quality aluminium by powder metallurgy technique. Firstly, the microstructures of the composites were investigated. Then, experiments were conducted to determine the specific heat of composite materials at different ambient temperatures together with thermal conductivity measurements. With the data obtained from the experiments, finite-element modelling was done and the thermal properties of the composite structure were optimised. In the microstructure studies, it was determined that with the increase in the B4C reinforcement ratio, the reinforcement agglomeration and porosity in the composite structure were found. As a result of the thermal experiments, it was observed that the thermal conductivity values of the composites were inversely proportional to the amount of B4C reinforcement and as the reinforcement ratio increased, the thermal conductivity values decreased. Besides, it was determined that the sintering temperature has an effect on the thermal conductivity value and that it increases the thermal conductivity of the composites with increasing sintering temperature. The highest heat conduction coefficient was obtained at 4% B4C reinforcement ratio and 600 °C sintering temperature. It was observed that the finite-element models prepared to determine the heat conduction coefficient effectively were consistent with the experimental results.

ÖzBu çalışmada, mühimmatın atış öncesinde, atış anında ve atış sonrasından fonksiyon gösterdiği süreye kadar, personel güvenliğini sağlayan topçu ve havan güvenlik ve kurma mekanizmalarında yer alan, pandül ve rotor ağırlıklarının kurulma süresine yani namlu önü emniyet mesafesine olan etkileri araştırılmıştır. Deneysel olarak yapılan bu çalışmada dönüsüz havan mühimmatlarında kullanılan havan tapasındaki pandüllerin ve dönülü topçu mühimmatlarında kullanılan topçu tapasındaki rotorların ağırlıkları değiştirilerek güvenlik ve kurma mekanizmalarının kurulma süreleri incelenmiştir. Pandüllerde %7-38'e kadar, rotorlarda ise %9-17'ye kadar ağırlık düşürülmüştür. Yapılan çalışma sonucunda pandüllerin ağırlıklarındaki azalışın tapa kurulma sürelerini azalttığı ancak rotorlarda ağırlık düşüşünün tapa kurulma süresini arttırdığı sonucuna varılmıştır. AbstractIn this study, the effects of pallet and rotor weights to the arming time, in other words muzzle safety, were investigated. Pallets and rotors are both located in the artilley and mortar SAD mechanisms which are used to provide safety of personnel before, during and after firing of the ammunition. In this experimental study, weights of the pallets have been altered for the smoothbore-mortar ammunition while similar changes have been applied to the weights of the rotors for the rifled-artillery ammunition and then, arming time of the SAD mechanisms were examined according to these changes. The weights have been reduced up to 7-38% for the pallets whereas up to 9-17% for the rotors. Eventually, it was concluded that arming time has been reduced by decreasing the weight of the pallets, however, arming time has been increased by applying the similar weight reduction operation to the rotors.