Development of a New Armor Steel and its Ballistic Performance

In this study, a boron added armor steel was developed according to standard rolled homogenous armor steel, MIL-A-12560, and metallographic-fractographic examinations were carried out to understand its deformation characteristics and perforation mode after interaction with a 7.62 mm armor piercing projectile. The microstructure of the developed steel was characterized by light and scanning electron microscope to evaluate its matrix after application of several heat treatments consisting of austenization, quenching and tempering. The mechanical properties of the developed steel were determined by tensile test at room temperature and notched impact test at -40 ºC. The ballistic performance of developed steel was determined by its V50 ballistic protection limit according to MIL-STD-662F standard and it was found to be higher than that of MIL-A-12560 steel. After perforation deformation induced adiabatic shear bands, that have an important role on the crack nucleation, were observed close to the penetration in the etched steel and perforation occurred by typical ductile hole enlargement with certain radial flows.Defence Science Journal, 2013, 63(3), pp.271-277, DOI:http://dx.doi.org/10.14429/dsj.63.134

Ballistic Impact Behaviour of a Tempered Bainitic Steel Against 7.62 mm Armour Piercing Projectile

In this study, occurence of failure after the interaction between an armour piercing 7.62 mm caliber projectile and a tempered bainitic steel has been investigated. The shot was performed at zero degree with a projectile velocity of 840 m/s. After the shot, microstructural and fractographical examinations were carried out on the sample taken from the perforated region. In the etched sample, it was observed that the morphology of the original microstructure had changed and adiabatic shear bands (ASBs) were formed in regions close to the direction of penetration. Main failure is ductile (plastic) deformation was followed by cleavage after shot. Cracks due to adiabatic shear band and formation of abrasive wear were seen. The perforation mode of the steel was a typical petalling.Defence Science Journal, 2011, 61(1), pp.81-87, DOI:http://dx.doi.org/10.14429/dsj.61.41

Matrix design of a novel ductile cast iron modified by W and Al: A comparison between thermodynamic modeling and experimental data

In high-temperature applications of ferrous materials, as in the case of exhaust manifolds, high thermal and mechanical stability are required. Stainless steels and Ni-resist alloys having austenitic matrices are good candidates to meet these requirements at elevated temperatures; however, they are expensive materials and present difficulties in casting. Ferritic ductile cast irons, like the commercial SiMo alloy, are comparatively cheaper materials with better castability but they cannot be used above approximately 800 °C. Thus, to meet the requirements with low-cost materials having improved high-temperature properties, new alloys must be developed by ferrite forming elements having the potential to increase equilibrium temperature. In this study, initially, a novel ductile cast iron matrix was designed using 1 W and 0-4 Al wt.-% and their phases stable at room temperature, transformation temperatures, solidification sequences and thermal expansivity values were determined using thermodynamic calculations with Thermo-Calc software. Computational studies revealed that (i) designed alloy matrices had graphite and M6C type carbides embedded in a ferritic matrix at room temperature as expected, (ii) A1 temperature increased as aluminum content increased. The obtained values were all above that of commercial SiMo alloy, (iii) the detrimental effect of increased aluminum addition on graphite content, and thermal expansivity was observed. Secondly, microstructural and thermal characterizations of cast alloys were performed for validation - the obtained data were in good agreement with the thermodynamic calculations

Tribological behavior of heat treated CuCrZr alloy

Optimal combination of strength, ductility and conductivity in CuCrZr alloy can be achieved by suitable heat treatment involving solution annealing at high temperature to dissolve alloying elements, water quenching to produce a super-saturated solid solution, and an aging treatment at an intermediate temperature to produce fine precipitates giving rise to high strength. In this study, Cu-1Cr-0.1Zr alloy was manufactured as cast material and following hot forging, solution annealing and aging were applied conventionally. In order to enhance the precipitation kinetics, solution annealed and quenched alloy was cold deformed and then aged at the same condition. Specimens obtained after (i) casting, (ii) conventional solution annealing and aging and (iii) aging after cold deformation were investigated in order to determine microstructural features, hardness and tribological properties. The results showed that while heat treatment process increased hardness the of cast specimen, it was enhanced further with deformation before aging. Besides hardness, tribological properties of the cast specimen were improved further by deformation before aging

Solidification and Microstructural Characterization on Atomized Powders

Powders produced by atomization techniques are commonly used in many industrial applications due to their many advantages such as homogeneous microstructure, low contamination and production of desired size range. In this study, the solidification of some ferrous and non-ferrous based alloy powders were considered and microstrucural characterization of all powder was carried out

Atomize Tozlarda Katılaşma ve Mikroyapısal Karakterizasyon

Atomizasyon teknikleri ile üretilen tozların homojen mikroyapı, düşük empürite içeriği ve arzulanan boyut aralığında üretimi gibi sunduğu birçok avantajlar doğrultusunda endüstriyel uygulamalarda kullanımı söz konusudur. Bu çalışmada santrifüj atomizasyonu ile üretilmiş demir ve demir dışı esaslı bazı alaşım tozlarının katılaşması irdelenmiş olup tüm tozların mikroyapısal karakterizasyonu gerçekleştirilmişti

Tribological behavior of heat treated CuCrZr alloy

Optimal combination of strength, ductility and conductivity in CuCrZr alloy can be achieved by suitable heat treatment involving solution annealing at high temperature to dissolve alloying elements, water quenching to produce a super-saturated solid solution, and an aging treatment at an intermediate temperature to produce fine precipitates giving rise to high strength. In this study, Cu-1Cr-0.1Zr alloy was manufactured as cast material and following hot forging, solution annealing and aging were applied conventionally. In order to enhance the precipitation kinetics, solution annealed and quenched alloy was cold deformed and then aged at the same condition. Specimens obtained after (i) casting, (ii) conventional solution annealing and aging and (iii) aging after cold deformation were investigated in order to determine microstructural features, hardness and tribological properties. The results showed that while heat treatment process increased hardness the of cast specimen, it was enhanced further with deformation before aging. Besides hardness, tribological properties of the cast specimen were improved further by deformation before aging

Characterization of the high temperature oxidation behavior of iron based alloys used as exhaust manifolds

Nowadays engine capacities of vehicles spread in a wide range due to different vehicle power demands. Power density of engines affects exhaust gas and therefore exhaust gas temperature varies from 650 °C to 1000 °C in exhaust manifolds. Depending on the exhaust gas temperature, different types of iron based alloys are used as manifold materials such as ferritic ductile cast irons (GGG40, SiMo), austenitic ductile cast irons (Ni-resist D5S), ferritic cast stainless steels (ACIHK30, AISI 409) and austenitic cast stainless steels (CF8C). In this study high temperature oxidation behavior of different cast alloys used as exhaust manifold materials like, (i) GGG40 ferritic ductile cast iron, (ii) SiMo ferritic ductile cast iron (iii) AISI 409 ferritic cast stainless steel and (iv) CF8C austenitic cast stainless steel, were investigated

Characterization of the high temperature oxidation behavior of iron based alloys used as exhaust manifolds

Nowadays engine capacities of vehicles spread in a wide range due to different vehicle power demands. Power density of engines affects exhaust gas and therefore exhaust gas temperature varies from 650 °C to 1000 °C in exhaust manifolds. Depending on the exhaust gas temperature, different types of iron based alloys are used as manifold materials such as ferritic ductile cast irons (GGG40, SiMo), austenitic ductile cast irons (Ni-resist D5S), ferritic cast stainless steels (ACIHK30, AISI 409) and austenitic cast stainless steels (CF8C). In this study high temperature oxidation behavior of different cast alloys used as exhaust manifold materials like, (i) GGG40 ferritic ductile cast iron, (ii) SiMo ferritic ductile cast iron (iii) AISI 409 ferritic cast stainless steel and (iv) CF8C austenitic cast stainless steel, were investigated