Theoretical Structural Metallurgy By Prof. A. H. Cottrell. Second edition. Pp. viii + 251. (London: Edward Arnold (Publishers), Ltd., 1955.) 25s. net.

/pdf/fundamentals-of-physical-metallurgy-1ezv48e8pg.pdf

Fundamentals of Physical Metallurgy

The ballistic performance of SiC–AA7075 functionally graded composite produced by powder metallurgy

Motivated by the considerable loss of the mechanical properties in the case of arc welding due to different precautions including adding under-matching filler metal, the feasibility of friction stir welding for joining ultrahigh mechanical properties steel has been demonstrated. The results indicated that the tool rotational speed and welding speed, as dominant parameters should be optimized for an improved weld quality, tool durability as well as productivity. A defect-free weld was produced on 2.2 mm plates of 1635 MPa quenched and tempered steel above A 1 transformation temperature at a welding speed of 600 mm/min and a tool rotational speed of 600 rpm. Acceptable mechanical properties comparable to those of the base metal were achieved for the stir zone due to the similarity in their microstructures. However, the overall tensile strength of the welded joint is negatively influenced by the remarkable decrease in the hardness of the HAZ. Based on these results, the FSW of 1635 MPa quenched and tempered steel appears feasible above A 1 , which is in contrast to other research works on different types of medium and high carbon steels where acceptable friction stir welds were successfully made below A 1 .

Investigation into feasibility of FSW process for welding 1600 MPa quenched and tempered steel

Ballistic impact performance of metallic targets

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.

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

In this study, a boron-alloyed experimental steel has been rolled to form a sheet product, and an austenization treatment has been performed, followed by rapid quenching and then tempering. By austenization, a homogeneous austenite phase is obtained and a martensitic microstructure is formed after rapid quenching. This kind of microstructure exhibits high hardness, but low toughness. Thus, a tempering heat treatment is applied at a proper temperature (200 °C and 600 °C) and various times, in order to provide optimum toughness and to develop an ideal combination of strength and toughness. After this process, at first the phases formed during the equilibrium state have been studied for the alloy system using ThermoCalc data, and also their amounts have been evaluated. The microstructures acquired after the heat treatments have been examined by light microscopy. The effects of the formed microstructures on mechanical properties are comparatively given by their strength, toughness, and elongation values. Furthermore, the failure mechanism with fractografical examinations has been determined by using a Scanning Electron Microscope (SEM).

Microstructural and Fractographical Studies on Quenched and Tempered Armor Steels

Gunumuzde metalik toz i s leme teknolojisine olan yonelimler ve bunun paralelinde malzeme uretimine yonelik ara s t i rma ve geli s tirme cal i s malar i h i z kazanm i s t i r. Metalik malzemelerin gunumuz endustrisinde kullan i m i ise seramik ve plastik malzemelere k i yasla geni s bir alan i kapsamaktad i r. Uzay, havac i l i k, askeri, otomotiv sanayisi ba s ta olmak uzere cok ce s itli alanlarda kullan i lan toz esasl i seri uretim parcalar i , konvansiyonel uretim sonras i elde edilen malzemelere gore co g u kez hem maliyet, hem de uretilebilirlik ozellikleri ac i s i ndan avantajl i bir konumdad i r. Bu cal i s mada, toz metalurjik malzemelerin prosesleme kademeleri ve ilgili toz boyutu ve boyut da g i l i m i , toz s ekli, tozun yuzey kalitesi ile uretim icin s ekillendirme bas i nc i , sinterleme s i cakl i g i ve zaman i tan i t i lm i s t i r. Bu konuda Ti6Al4V, IF ve molibden onala s i ml i celik esasl i malzemeler uzerine orneklemeler yap i lm i s ve varolan ili s kilerin alt i cizilmi s tir.

/pdf/metalik-toz-isleme-teknolojisi-ve-prosesleme-kademeleri-2su4yk9d3f.pdf

Metalik Toz İşleme Teknolojisi Ve Prosesleme Kademeleri Açısından Parametrik İlişkiler

In the study for this contribution, good mechanical properties have been obtained from Mo (and Cu) alloyed PM-steels after suitable heat treatment. The influence of two to four weight percent nickel additions in these Mo (and Cu) alloyed PM-steels on the mechanical properties have been studied. The influence of such an alloying modification on the defect characteristics has also been investigated. The heat treatment of the steel material has been realized via a novel way, i.e. with the sinter-hardening method. The mechanical properties like tensile strength, matrix microhardness, and toughness have been measured. Transverse rupture tests have been implemented for toughness measurement while the transverse rupture strength data has been obtained by using the Weibull statistics. Microstructural studies have been performed with various microscopy techniques, where the general steel matrix was observed to exist of tempered martensite, bainite, residual austenite, and micropores. The amount of pores w...

Effect of Nickel Addition and Porosity on Fracture Behaviour of Molybdenum Alloyed Powder Metallurgical Steel

Bu calismada, son yillarda onem kazanan bir malzeme haline gelmis SiC icerikli metal matriks kompozitler ile calisilmis ve yaklasik nanoboyutlu SiC katkisi ile Al-matriksli uygun bir toz metalurjik malzeme uretilmeye calisilmistir. Bu amacla yaklasik 1 µm boyutunda SiC tozu kullanilmis ve matriks malzemesi olarak AlCu4Mg1 alasimi secilmistir. Kullanilan alasim pota icinde ergitildikten sonra batirma yoluyla ergiyige katilan SiC toz yigini mekanik karistirma yontemiyle homojen bir sekilde dagitilmis ve nihai ergiyik silindirik kaliba dokulmustur. Katilasan malzeme yaklasik 430 oC’de ekstruze edilmis ve 55 mm capli cubuk halinde uretilmistir

/pdf/al-sic-tozlarinin-prep-atomizasyonu-ile-uretimi-1mq6170oq8.pdf

Şadi Karagöz

Papers

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

Microstructural and Fractographical Studies on Quenched and Tempered Armor Steels

Metalik Toz İşleme Teknolojisi Ve Prosesleme Kademeleri Açısından Parametrik İlişkiler

Effect of Nickel Addition and Porosity on Fracture Behaviour of Molybdenum Alloyed Powder Metallurgical Steel

Al-Sic Tozlarinin Prep Atomizasyonu İle Üretimi