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The strengthening effects of Cu and Mn were studied in steels, which contained 0.2% C and were micro-alloyed with B and Ti. The experimental steels were austenitized and quenched in order to take Mn and Cu into solid solution. The subsequent tempering of martensitic structures resulted in higher strengths in the materials alloyed with Cu than in the steel without Cu addition. Tensile testing and metallographic analyses were performed. The kinetics and magnitude of precipitation strengthening were measured for different tempering temperatures and times. Presumed synergistic effects between Cu precipitation strengthening and higher levels of Mn were observed.

Cu precipitation strengthening was compared in steels after treatments with and without cold rolling. A 0.2% C steel containing up to 1.5% Cu was quenched and tempered. Cu precipitation took place during tempering and increased its yield strength (YS). Quenched and tempered samples were compared with samples where cold rolling was performed between quenching and tempering. They exhibited significantly different mechanical properties. In addition, Cu alloying influenced the properties of each group of samples in different ways. The quenched and tempered samples exhibited behavior that is typical of precipitation hardening. Cu caused yield strength to increase with tempering temperature and time. The cold rolling of martensite reduced the maximal Cu-related strengthening and also eliminated its time and temperature dependence.

Manganese twinning induced plasticity (TWIP) steels are attractive materials for the automotive industry thanks to their combination of strength and excellent toughness. This article deals with basic microstructural and mechanical properties of sheet metal of two heats of low-carbon medium-manganese steel with different aluminium levels. Microstructure observation was carried out using optical and scanning electron microscopy. Electron backscatter diffraction (EBSD) and X-ray diffraction were used for phase analysis. In an experiment that focused on the weldability of both materials, sheet metals were laser-welded using various laser power settings, with and without shielding gas. Various combinations of joints between materials of the two heats and sheet metal conditions were tested (work-hardened upon cold rolling + annealed). Mechanical properties of the weld joints were determined using miniature tensile testing and conventional hardness measurement. The strengths of miniature specimens of the weld metal were very close to the strength of the base material.

The thermomechanical processing of a nickel-based superalloy is the way to considerably influence the grain size. A uniform coarse-grain size increases the creep strength and the crack-growth resistance. In this work, the processing for achieving a uniform recrystallized-grain structure with a variation in the thermomechanical parameters is investigated. The MoNiCr alloy is intended for modern designs of nuclear reactors, in which molten fluoride salts are used as the coolants in the primary and/or secondary circuit. It represents a material alternative with a high corrosion resistance in the area of fluoride salts and it has very good creep properties in the temperature range of 650-750°C as well. The manufacture of vessels and fittings from the MoNiCr alloy requires the mastering of the technology for forming this high-alloyed material. The key step seems to be the transition of the cast state of the material to the state of a cast recrystallized microstructure with homogenous fine grains. A particular stress condition is, besides the temperature, very important during hot forming. Nickel alloys are able to accept a significantly higher deformation level if the compressive stress prevails. A forming process involving the compression state of stress increases the probability that the material will reach, without failure, a level of deformation that allows recovery and recrystallization processes. A particular deformation process was carried out on a physical simulator. The preceding cold deformation essentially accelerates the recrystallization process of a deformed cast structure. Keywords: recrystallization, nickel alloys, physical simulation Termomehanska obdelava superzlitine na osnovi niklja je na~in, s katerim lahko mo~no vplivamo na velikost kristalnih zrn. Enakomerna velikost velikih zrn pove~uje odpornost na lezenje in ovira rast razpok. V tem delu je s spreminjanjem parametrov termomehanske predelave preiskovana predelava za doseganje enakomerne rekristalizirane mikrostrukture. Zlitina MoNiCr je namenjena modernemu konceptu nuklearnih reaktorjev, v katerih se uporablja staljene fluoridne soli, kot sredstvo za hlajenje v primarnem in/ali sekundarnem tokokrogu. Predstavlja alternativni material z visoko korozijsko odpornostjo v podro~ju fluoridnih soli in ima hkrati zelo dobro odpornost na lezenje v temperaturnem podro~ju 650-750°C. Izdelava posod in prirobnic iz zlitine MoNiCr zahteva obvladovanje tehnologije preoblikovanja tega visoko legiranega materiala. Klju~ni moment izgleda je preoblikovanje litega stanja materiala do stanja rekristalizirane mikrostrukture s homogenimi, drobnimi zrni. Pri vro~em preoblikovanju je poleg temperature pomembno tudi stanje napetosti. Nikljeve zlitine so sposobne veliko ve~je deformacije,~e prevladujejo tla~ne napetosti. Preoblikovanje s tla~nimi napetostmi pove~uje verjetnost, da bo material brez poru{itve dosegel tak nivo deformacije, ki omogo~a procese poprave in rekristalizacije. Proces deformacije je bil izvr{en na fizikalnem simulatorju. Nadaljnja hladna deformac...