23 KB880 KB21 KB200020242000Asanovic, VanjaBošnjak, BrankaHarding, RichardPop-Tonev, KiroRadulović, Brankoletnik:34številka:56 stranistr. 207-212ISSN:1580-2949COBISSID:234154URN:URN:NBN:SI:doc-73BFJILOenInštitut za kovinske materiale in tehnologijeMateriali in tehnologijeavstenitlitinemehanske lastnostitempranjevpliv temperatureThe influence of austenitising temperature on the microstructure and mechanical properties of low-alloyed Ni-Mo-Cu austempered ductile iron| Vpliv temperature austenitizacije na mikrostrukturo in mehanske lastnosti malolegirane NiMoCu austemprane duktilne železove litine|In the present study we have investigated the effect of austenitising temperature and austempering time on the microstructure and mechanical properties of low-alloyed Ni-Mo-Cu ductile iron. The specimens were austenised at 850, 875, 900 and 930°C for 120 min, then austempered for 10, 30,60, 120, 240 and 360 min at 350°C, and examined by optical and scanning electron microscopy. The volume fraction of retained austenite, bainite, martensite and austenite-carbon content results were then correlated with microstructural changes, the kinetics of transformation and impact toughness. Following short periods of austempering time, the carbon content of the retained austenite is low and on subsequent cooling to room temperature it transforms to martensite, resulting in low impact values. The carbon content of the austenite was evaluated by measuring the latice parameters using X-ray diffraction. Optimum properties were obtained at 900°C for intermediate austempering periods (120-240 min)Raziskan je vpliv temperature austenizacije in austempering časa na mehanske lastnosti malo legirane NiMoCu duktilne litine. Vzorci so bili ogrevani 120 min pri 850, 875, 900 in 930°C ter nato austempirani 10, 30, 60, 120, 240 in 360 min pri 350°C ter preiskani v optičnem in vrstičnem elektronskem mikroskopu. Volumski delež zadržanega austenita, bajnita, martenzita in vsebnosti ogljika v austenitu so bili korelirani s spremembami mikrostrukture, kinetiko premene in udarno žilavostjo. Po kratkih časih austenitizacije je vsebnost ogljika v zadržanem austenitu majhna in pri ohlajanju na sobno temperaturo premeni v martenzit, kar povzroča majhno žilavost. Vsebnost ogljika v austenitu je bila določena z določitvijo parametra mreže z difrakcijo X žarkov. Optimalne lastnosti so bile dosežene pri 900°C za vmesne čase austempiranja (120-140 min)TEXTznanstveno časopisjejournalsSlovenian National E-content AggregatorNational and University Library of SloveniaInštitut za kovinske materiale in tehnologije