Microstructural Characterization of Cu-Al-Mn-Zn Alloy

U okviru ovog diplomskog rada provedena je mikrostrukturna karakterizacija Cu-Al-Mn-Zn legure proizvedene na tri različita načina: taljenjem i lijevanjem u laboratorijskoj elektrolučnoj peći - ingot, postupkom brzog skrućivanja - traka i vertikalnim kontinuiranim lijevanjem - štap. Mikrostrukturna karakterizacija je obuhvaćala optičku mikroskopiju, pretražnu elektronsku mikroskopiju, energijsko disperzijsku spektrometriju, diferencijalno pretražnu kalorimetriju te je provedeno i mjerenje mikrotvrdoće. Sva ispitivanja su provedena na lijevanim i toplinski obrađenim uzorcima (900 °C/30min/voda). Navedena ispitivanja su provedena s ciljem utvrđivanja mogućnosti proizvodnje Cu-Al-Mn legure s prisjetljivosti oblika uz dodatak 3,2% Zn. Optičkom i pretražnom elektronskom mikroskopijom primijećena je prisutnost jednofazne mikrostrukture (α-faza). Energijsko disperzijskom spektrometrijom utvrđena je znatna heterogenost legura. Nakon toplinske obrade uočeno je djelomično poboljšanje homogenosti istraživanih legura. Toplinskom obradom nije se uspjela dobiti martenzitna mikrostruktura, tj. i nakon kaljenja mikrostruktura se sastojala samo od α-faze. DSC analizom određene su temperature egzotermnih i endotermnih pikova na krivuljama zagrijavanja i hlađenja. Mikrotvrdoća Cu-Al-Mn-Zn legure proizvedene u vakuumskoj elektrolučnoj peći je iznosila 685,6 HV10. Nakon toplinske obrade dolazi do znatnog smanjenja mikrotvrdoće legure proizvedene vertikalnim kontinuiranim lijevanjem (517,5 HV10), dok legura proizvedena u vakuumskoj elektrolučnoj peći zadržava približno istu vrijednost mikrotvrdoće (693,6 HV10).Within this graduate thesis the microstructural characterization of Cu-Al-Mn-Zn alloy was performed in three different methods: melting and casting in a laboratory electric arc furnace - ingot, rapid solidification method - ribbon, and with vertical continuous casting - bar. Microstructural characterization included optical microscopy, scanning electron microscopy, energy dispersion spectrometry, differential scanning calorimetry and measurement of microhardness. Investigation was performed on as-cast and heat-treated samples (900 °C/30min/water quenching). The above-mentioned investigations were carried out to determine the possibility of producing Cu-Al-Mn shape memory alloy with the addition of 3.2% Zn. Optical and scanning electron microscopy showed the presence of single phase microstructure (α-phase). Energy dispersion spectrometry determined a considerable heterogeneity of the alloy. After heat treatment, partial improvement of the homogeneity of the investigated alloys was observed. Martensitic microstructure was not obtained by heat treatment, i.e. even after the quenching microstructure consisted of α-phase only. By DSC analysis exothermic and endothermic peak temperatures on heating and cooling curves were determined. Microhardness of Cu-Al-Mn-Zn alloy produced in vacuum electric arc furnace was 685.6 HV10. After heat treatment, a substantial reduction in the microhardness of the alloy produced by vertical continuous casting (517.5 HV10) is achieved, while the alloy produced in vacuum electric arc furnace retains approximately the same value of microhardness (693.6 HV10)