1554 KB16 KB200020262014Aišman, DavidJirková, HanaMašek, Bohuslavletnik:48številka:5str. 719-723COBISSID:1096106ISSN:1580-2949URN:URN:NBN:SI:doc-SR9IWKYMenInštitut za kovinske materiale in tehnologijeMateriali in tehnologije30MnVS6high pressure torsionminithixoformingplastična deformacijapreoblikovanje v testastem stanjusevere plastic deformationtorzija pri visokem tlakuEffect of the initial microstructure on the properties of low-alloyed steel upon mini-thixoforming| Vpliv začetne mikrostrukture na lastnosti malolegiranega jekla po predelavi mini-thixoforming|Thixoforming is an unconventional forming process based on semi-solid processing. Semi-solid processing involves heating the feedstock to a temperature at which it becomes partly liquid and partly solid. Thanks to partial melting and rapid solidification, unconventional microstructures can be obtained even in conventional materials. Today%s research efforts mainly involve high-alloyed steels with a wide freezing range at lower temperatures. By contrast, low-alloyed steels with the solidification temperatures above 1400 °C are not under extensive investigation. The main objective of the study was to find whether and how the attributes of the feedstock microstructure can be transmitted to the final semi-solid processed microstructure of the 30MnVS6 microalloyed steel. The first stage of the experiment involved mini-thixoforming of the as-received specimens of the steel. In order to assess the effects of the initial microstructure, specimens with three types of microstructure were prepared with high-pressure torsion (HPT), a severe-plastic-deformation (SPD) technique. Initial and final microstructures were examined using light and electron microscopes and image-analysis techniques. The phase composition was determined with the aid of the X-ray diffraction analysis. The mechanical properties were determined with tensile and hardness testing. Information on the local properties and the properties of microstructure constituents was obtained with microhardness measurementThixoforming je neobičajen postopek preoblikovanja, ki temelji na preoblikovanju v testastem stanju. Preoblikovanje v testastem stanju vključuje ogrevanje preoblikovanca do temperature, pri kateri postane material delno v staljenem in delno v strjenem stanju. Po zaslugi delnega taljenja in hitrega strjevanja se lahko doseže neobičajne mikrostrukture celo pri navadnih materialih. Sedanje raziskave se izvajajo večinoma na močno legiranih jeklih s širokim intervalom strjevanja pri nižjih temperaturah. Nasprotno se malolegirana jekla s temperature strjevanja nad 1400 °C ne preiskuje intenzivno. Glavni cilj te študije je ugotoviti, ali in kako atribute mikrostrukture surovca prenesti po preoblikovanju v testastem stanju pri mikrolegiranem jeklu 30MnVS6. Prva stopnja eksperimentov je vključevala minithixoforming preoblikovanje dobavljenih vzorcev jekla. Za oceno vpliva začetne mikrostrukture so bili pripravljeni vzorci s tremi vrstami mikrostrukture s torzijo pri visokem tlaku (HPT), to je s tehniko velike plastične deformacije (SPD). Začetne in končne mikrostrukture so bile preiskane s svetlobno mikroskopijo, z elektronsko mikroskopijo in s tehnikami analize slik. Sestava faz je bila določena z rentgensko difrakcijsko analizo. Mehanske lastnosti so bile določene z nateznim preizkusom in z merjenjem trdote. Informacija o lokalnih lastnostih in lastnostih posameznih mikrostrukturnih faz je bila dobljena z meritvami mikrotrdoteTEXTznanstveno časopisjejournalsSlovenian National E-content AggregatorNational and University Library of SloveniaInštitut za kovinske materiale in tehnologije