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In this work we studied the response of newly developed armored steel plates PROTAC 500 to the ballistic testing with armored piercing bullets with a core of tungsten carbide, charge 7.62 mm. Interactions between the bullets and the steel plate was investigated by standard metallographic and mechanical testing methods. We were interested in the geometric features of interaction, the phenomenon of adiabatic shear bands (ASB), cracks and local failure, local melting and interaction of the components and plate with metal balls fragments in the melt, rate of deformation and the steel hardening.

The paper presents comparison of microstructure and hardness of Cu-Al-Ni shape memory alloy before and after heat treatment (quenching at 900°C/60 min/water and tempering at 300°C/60 min/water). Microstructural analysis was obtained by optical microscopy (OM) and scanning electron microscopy (SEM) equipped with energy dispersive spectrometry (EDS). Before heat treatment (casted and forged state) the sample has a partially martensitic microstructure with presence of γ2 phase, while on samples after the heat treatment completely martensitic microstructure with inclusions of complex chemical composition was observed. These inclusions can have a potential unwanted influence on alloys properties. Hardness of the alloy before heat treatment was 344.3 HV0.5, after quenching was 229.6 HV0.5 and after tempering was 300.2 HV0.5.

The group of steels intended for the production of bolts and nuts from the production programme of the Zenica Steel Plant, Zenica, nowadays called Arcelor Mittal Zenica, includes, among others, the steel C8C according to EN 10263-2. In this paper, the results of testing the above-mentioned steel, with the nitrogen content of more than 0.007 %, manufactured within a specifically defined technological programme, are presented. The testing of the rolled bars with a diameter of 12 mm is focused, among the mechanical and metallographic tests, especially on the technological compression test in the cold state that is normally performed as an additional control test in the production. The cold compression of the test samples has been performed in four degrees of deformation and at two different speeds of compressing tools. We determined the dependence of the resistance to deformation of the material on the degree and speed of deformation. The surface inspection of the tested samples was performed with visual control with the aim to determine deformability of the bars produced in this way. Skupina jekel, namenjena za izdelavo vijakov in matic iz proizvodnega programa Železarne Zenica iz Zenice, danes Arcelor Mittal Zenica, vsebuje med drugim tudi jeklo C8C, skladno s standardom EN 10263-2. V članku so predstavljeni rezultati preizkušanja omenjenega jekla z vsebnostjo dušika več kot 0,007 %, izdelanega po posebni tehnologiji. Preizkušanje valjanih palic premera 12 mm je poleg metalografskih in mehanskih preizkusov usmerjeno predvsem na tehnološki tlačni preizkus v hladnem, kar se navadno izvaja kot dodatni kontrolni preizkus v proizvodnji. Preizkus hladnega stiskanja vzorcev je bil izvršen s štirimi stopnjami deformacije in pri dveh hitrostih stiskanja. Določena je bila odvisnost med odpornostjo proti deformaciji materiala, stopnji deformacije in hitrosti deformacije. Ocena površine preizkušancev je bila izvršena z vizualnim nadzorom z namenom, da se ugotovi deformabilnost palic.

U radu su prikazani razultati mikrostrukture i tvrdoće lijevanih slitina CuAlNi i CuAlNiMn s prisjetljivosti oblika. Taljenje slitina provedeno je u vakuum indukcijskoj peći u zaštitnoj atmosferi argona. Slitine su lijevane u ingote mase 15 kg. Mikrostrukturna karakterizacija provedena je metodom optičke mikroskopije (OM) i pretražne elektronske mikroskopije (SEM) opremljene s energetski disperzijskim spektrometrom (EDS). Djelomično martenzitna mikrostruktura uočena je u CuAlNiMn slitini, u odnosu na dvofaznu mikrostrukturu slitine CuAlNi. Mjerenje tvrdoće slitina provedeno je Vickersovom metodom. Tvrdoća CuAlNiMn slitine bila je 333 HV5, a slitine CuAlNi 475 HV5.

In this paper the results of microstructure and hardness of CuAlNi and CuAlNiMn shape memory as- casted state alloys is presented. Melting of the alloys was carried out in vacuum induction furnace in protective atmosphere of argon. Alloys were casted into ingots with 15 kg weight. Microstructural characterization was obtained by optical microscopy (OM) method and scanning electron microscopy (SEM) method equipped with energy dispersive spectrometry (EDS). Partially martensitic microstructure in CuAlNiMn alloy was observed, while the two phase microstructure in CuAlNi alloy was found. A hardness measurement was performed by Vickers method. Hardness of CuAlNiMn alloy was 333 HV 0, 5 and CuAlNi alloy was 475 HV 0, 5.

U radu je prikazan dio istraživanja slitina s prisjetljivosti oblika na bazi bakra, primarno CuAlNi i CuAlNiMn slitina. Slitine su pripremljene vakuum indukcijskim taljenjem komponenti u zaštitnoj atmosferi argona, te lijevane u ingot mase oko 15 kg. Prikazana je mikrostrukturna karakterizacija (optička i pretražna elektronska mikroskopija) navedenih slitina u lijevanom stanju kojom je utvrđena dvofazna mikrostruktura kod CuAlNi slitine, te djelomično martenzitna mikrostruktura kod CuAlNiMn slitine. EDS analiza je pokazala prisutnost faze s povećanim sadržajem aluminija u obje slitine. Mjerenje mikrotvrdoće slitina provedeno je Vickersovom metodom. Tvrdoća CuAlNi slitine iznosila je 475 HV0.5, a CuAlNiMn slitine 333 HV0.5.

The superalloy Nimonic 80A has found its major application in the production of the parts for the vehicle and airplane industries. It is a relatively expensive material and it is very important to reduce its production costs to acceptable levels. The aim of this research was to produce the superalloys with varying supplements of alloying elements. The investigations carried out included chemical testing and the testing of the mechanical properties of the superalloy Nimonic 80A, followed by a regression analysis of the obtained data to show the influence of certain alloying elements that can significantly affect the improvement of the mechanical properties of Nimonic 80A. The results of the regression analysis are the equations with which, on the basis of the known chemical composition, i.e., the content of the main alloying elements - Al, Ti and Co - the mechanical properties of the materials at increased temperatures can be predicted. On the basis of the obtained squared regression equations, an optimization of the chemical composition for the selected values of the mechanical properties was carried out. Glavni področji za uporabo in izdelavo delov iz superzlitine Nimonic 80A sta avtomobilska in letalska industrija. Zlitina je relativno drag material, zato je zelo pomembno, da se zmanjšajo stroški njene proizvodnje na sprejemljiv nivo. Namen te raziskave je bila izdelava superzlitine z različnim dodatkom legirnih elementov. Opravljene preiskave so vključevale kemijsko analizo in preskušanje mehanskih lastnosti superzlitine Nimonic 80A, sledila pa je regresijska analiza dobljenih podatkov, da bi pokazali vpliv legirnih elementov na izboljšanje mehanskih lastnosti Nimonic 80A. Rezultati regresijske analize so enačbe, ki omogočajo napovedovanje mehanskih lastnosti zlitine pri povišanih temperaturah na podlagi kemijske analize, to je vsebnosti legirnih elementov Al, Ti in Co. Na podlagi dobljenih regresijskih enačb je bilo izvršeno optimiranje kemijske sestave za izbrane vrednosti mehanskih lastnosti.

Industry has a permanent need for new materials to improve the performance of constructions. However, the development of new materials is a complicated and costly process, and in many cases the existing materials with modified characteristics are used. By the use of certain technological processes of producing liquid metals, deformation processes, thermal and surface treatments, the mechanical and exploitation characteristics of existing materials can be improved. In this paper is an overview of several research activities at the Institute in Zenica with the goal to improve the characteristics of some materials in use in the air and car industries. With semi-industrial facilities and in laboratories of the institute some researches where conducted on stainless steels and maraging steels as well as on superalloys based on nickel and iron. Industrija potrebuje nove materiale, če želi izboljšati lastnosti konstrukcij. Razvoj novih materialov je zapleten in drag proces in so zato mnogokrat uporabljeni materiali s spremenjenimi lastnostmi. Z spremembami v tehnologiji obdelave taline, procesov predelave, toplotne in površinske obdelave je mogoče izboljšati mehanske in uporabne lastnosti materialov. V tem delu je kratek pregled raziskav na Inštitutu v Zenici, ki so bile izvršene s ciljem izboljšanja materialov, ki so v uporabi v industriji vozil in letal. Na polindustrijskih in laboratorijskih napravah na inštitutu so bile opravljene raziskave na nerjavnih in maraging jeklih in na superzlitinah niklja in železa.