Influence of zirconium content and heat treatment on the microstructure and hardness of Cu-Al-Mn-Zr alloys with shape memory

U ovom radu su predstavljeni rezultati uĉinka toplinske obrade na mikrostrukturu i mikrotvrdoću legura Cu-8.5Al-10Mn- (0.25-1) Zr. Ingoti (promjera 8 mm i duljine 15 mm) dobiveni su postupkom taljenja i lijevanja. Proizvodnja ispitivanih legura izvodila se u laboratorijskoj elektroluĉnoj peći. Taljenje se odvijalo elektriĉnim lukom u vodom hlaĊenom bakrenom kalupu koji se ujedno koristio i kao kalup za lijevanje uzorka. Uzorci su analizirani u lijevanom stanju nakon toplinske obrade 900 °C/ 15 min / voda. Mikrostrukturna analiza provedena je optiĉkim mikroskopom (OM), skenirajućim elektronskim mikroskopom (SEM) koji je opremljen ureĊajem za energetski disperzijsku spektroskopiju (EDS). Preliminarna analiza rezultata optiĉke mikroskopije ispitivanih legura potvrdila je da se mikrostruktura sastojala od martenzita samo u leguri Cu-8.5Al-10Mn-0.25Zr i u lijevanom i u toplinski obraĊenom stanju. SEM analiza je pokazala poĉetak stvaranja martenzita na pojedinim mjestima u svim ispitivanim legurama u lijevanom i toplinski obraĊenom stanju. Mjerenje mikrotvrdoće izvedeno je Vikersovom metodom. Vrijednosti mikrotvrdoće legura Cu-8.5Al-10Mn-(0.25-1) Zr bile su do 215.8 HV1 nakon lijevanja i do 224,5 HV1 nakon toplinske obrade.In this work, the results of the effect of heat treatment on the microstructure and microhardness of Cu-8.5Al-10Mn- (0.25-1) Zr alloys are presented. Ingots (diameter 8 mm and length 15 mm) were obtained by melting and casting. The production of the tested alloys was performed in a laboratory electric arc furnace. Melting was performed with electric arc in a water-cooled copper mold which was also used as a mold for casting the sample. Samples were analyzed in the cast state after heat treatment at 900 ° C / 15 min / water. Microstructural analysis was performed by optical microscope (OM), scanning electron microscope (SEM) equipped with an energy dispersive spectroscopy (EDS) device. Preliminary analysis of the optical microscopy of the examined alloys confirmed that the microstructure consisted of martensite only in the Cu-8.5Al-10Mn-0.25Zr alloy in both cast and heat-treated states. SEM analysis showed the beginning of the formation of martensite in some places in all tested alloys in the cast and heat-treated state. The measurement of microhardness was performed by the Vickers method. The microhardness values of Cu-8.5Al-10Mn-(0.25-1) Zr alloys were up to 215.8 HV1 after casting and up to 224.5 HV1 after heat treatment