Properties of Cu-Al-Mn shape memory alloy after cold drawing

U ovom radu provedena je mikrostrukturna karakterizacija Cu-Al-Mn legure s prisjetljivosti oblika. Legura Cu-11,9Al-2,5Mn (mas. %) s prisjetljivosti oblika dobivena je postupkom vertikalnog kontinuiranog lijevanja u obliku šipke promjera 8 mm. Procesom toplog valjanja i kovanja u profiliranom alatu dobivena je šipka promjera 4,80 mm. Šipka je zatim bila podvrgnuta procesu hladnog vuĉenja ĉime je dobivena ţica promjera 4,47 mm, 3,22 mm i 1,80 mm. IzmeĊu provlaka hladnog vuĉenja uzorci su bili toplinski obraĊeni na 580 °C/60 minuta i 600 °C/60 minuta. Mikrostrukturna karakterizacija uzoraka provedena je optiĉkom svjetlosnom mikroskopijom (OM) i pretraţnom elektronskom mikroskopijom (SEM) s energijsko disperzijskom spektrometrijom (EDS). Detaljnom analizom mikrostrukture zamijećena je dvofazna (α + β) mikrostruktura u lijevanom stanju, dok uzorci nakon hladnog vuĉenja pokazuju dvofaznu (martenzit + α) mikrostrukturu. Odabrani uzorci su zatim bili podvrgnuti postupku toplinske obrade na 900 °C/15 minuta te su naglo ohlaĊeni u vodi sobne temperature. OM i SEM analizom uzoraka vidljiva je martenzitna mikrostruktura koja nastaje kao posljedica hlaĊenja legure iz β-faznog podruĉja. Mikrotvrdoća uzoraka raste sa smanjenjem promjera ţice. Uzorci nakon toplinske obrade pokazuju niţe vrijednosti mikrotvrdoće u odnosu na uzorke nakon hladnog vuĉenja.In this paper, microstructural characterization of Cu-Al-Mn shape memory alloy was performed. The Cu-11.9Al-2.5Mn (wt.%) shape memory alloy was produced by vertical continuous casting technique obtaining bars of 8 mm in diameter. With the process of hot rolling and forging in a profiled tool the 4.80 mm bar was produced. The bar was then subjected to a cold drawing process to obtain a wire of 4.47 mm, 3.22 mm and 1.80 mm in diameter. Between cold drawing runs, the samples were heat treated at 580 °C/60 minutes and 600 °C/60 minutes. Microstructural characterization of the samples was performed by optical microscopy (OM) and scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS). A detailed analysis of the microstructure revealed a two-phase (α + β) microstructure in the as-cast state, while the samples after cold drawing showed a two-phase (martensite + α) microstructure. The selected samples were then subjected to heat treatment procedure at 900 °C/15 minutes which was followed by rapid cooling in room temperature water. OM and SEM analysis of the samples revealed a martensitic microstructure as a result of cooling the alloy from the β-phase region. The microhardness of the samples increases with decreasing wire diameter. Samples after heat treatment show lower values of microhardness compared to samples after cold drawing