Microstructural characterization of Cu82.3Al8.3Mn9.4 shape memory alloy after rolling

Abstract

In this paper, the microstructure of Cu82.3Al8.3Mn9.4 (in wt. %) shape memory alloy after hot and cold rolling was investigated. The Cu82.3Al8.3Mn9.4 alloy was produced by a vertical continuous casting method in the form a cylinder rod of 8 mm in diameter. After the casting, hot and cold rolling was performed. By hot rolling a strip with a thickness of 1.75 mm was obtained, while by cold rolling a strip with a thickness of 1.02 mm was produced. After the rolling process, heat treatment was performed.Heat treatment was carried out by solution annealing at 900 °C held for 30 minutes and water quenched immediately after heating. The microstructure characterization of the investigated alloy was carried out by optical microscopy (OM), scanning electron microscopy (SEM) equipped with a device for energy dispersive spectroscopy (EDS). Phase transformation temperatures and fusion enthalpies were determined by differential scanning calorimetry (DSC) method. The homogenous martensite microstructure was confirmed by OM and SEM micrographs after casting. During rolling the two-phase microstructure occurred. Results of DSC analysis showed martensite start (Ms), martensite finish (M f ), austenite start (A s ) and austenite finish (A f ) temperatures.

Razvoj legura s prisjetljivošću oblika na bazi bakra u okviru znanstveno-istraživačkih projekata na Metalurškom fakultetu Sveučilišta u Zagrebu

“…31 Analizirana je i kontinuirano lijevana šipka SMA legure Cu-8,3Al-9,4Mn nakon tople deformacije (kod 880 °C) u traku debljine 1,75 mm te nakon hladnog valjana u traku do debljine 1,02 mm. 37 Nakon toplog deformiranja temperatura martenzitne transformacije pomaknuta je prema višim temperaturama u odnosu na temperaturu M s za nedeformirano lijevanu šipku. Nakon toplog deformiranja temperatura početka nastajanja martenzita M s = 53 °C, dok je nakon hladnog deformiranja M s = 44 °C.…”

“…Rezultati ispitivanja legura klasično lijevanih u bakreni kalup (ingot φ8 mm) pokazali su da je mikrotvrdoća Cu-13Al-2,5Mn-2Ni dostigla najveću vrijednost u austenitiziranom i naknadno gašenom stanju (285,6 HV1). [45][46][47][48][49][50][51]52 Vrijednost mikrotvrdoće u lijevanom stanju bila je 260 HV1. Ispitivanje mikrotvrdoće Cu-9Al-7Mn-0,4Ti ingota φ8 mm pokazalo je najveću vrijednost nakon austenitizacije i naknadnog gašenja (263,6 HV1), dok je mikrotvrdoća u lijevanom stanju bila 213,2 HV1.…”

“…57 Slika 9 prikazuje rezultate di-namičko-mehaničke analize kontinuirano lijevane legure Cu-8,3Al-9,4Mn nakon austenitizacije i naknadnog gašenja s 900 °C. 58 Promjena u modulu pohrane (E') pokazuje austenitnu transformaciju pri −20 °C s maksimalnim intenzitetom pri 31 °C (slika 9a). Krivulja promjene modula pohrane s temperaturom (slika 9a) pokazuje austenitnu transformaciju, s obzirom na to da legura Cu-8,3Al-9,4Mn u tom temperaturnom području pri zagrijavanju pokazuje isključivo austenitnu transformaciju, što je potvrđeno i DSC rezultatima 46 te legure, kao i mikrostrukturnom analizom legure.…”

“…21,[37][38][39][40] Analiza tih legura tehnikom DSC pokazala je martenzitnu transformaciju u lijevanom stanju samo u legurama pripremljenim kontinuiranim lijevanjem i tehnologijom "melt-spinning". Kontinuirano lijevana legura pokazala je nižu temperaturu početka martenzitne transfor-…”