Ispitivanje ojačavanja starenjem legura sistema Au-Ag-Cu za proizvodnju nakite
Investigation of age-hardening of alloy systems Au-Ag-Cu for jewelry production
Doktorand
Perić, Radiša S.Mentor
Gusković, DragoslavČlanovi komisije
Marković, DesimirIvanov, Svetlana
Stojadinović, Slobodan
Jovančićević, Branimir
Metapodaci
Prikaz svih podataka o disertacijiSažetak
Proizvesti nakit od komada čistog zlata, iziskuje znanja iz različitih oblasti nauke,
počev od metalurgije, fizičke hemije, mašinstva, preko medicine, pa do nauke o dizajnu
i estetskim zahtevima, pri tome uvek uključujući i istoriju umetnosti. Sa stanovišta
metalurgije, u disertaciji su razmotreni i eksperimentalno istraženi neki od veoma
značajnih, ali nedovoljno izučenih aspekata, vezanih za pojedine faze proizvodnje
nakita od legura na bazi zlata i srebra.
Predmet ovog rada usmeren je na izučavanje, definisanje i optimizaciju najznačajnijih
uticajnih parametara na finalna svojstva i kvalitet višekomponentnih legura sistema Au-
Ag-Cu, u okviru istraživanja relacije: hemijski sastav – termička obrada –
mikrostruktura – tvrdoća – električna provodljivost. Sve ovo zahteva multidisciplinaran
pristup problemima proizvodnje nakita, posebno što nakit ispunjava potrebe čoveka za
lepim.
Proučavane su tri grupe legura, shodno zakonskoj regulativi u Republici Srbiji, i
potrebama tržišta. Legura... ,,žute“ boje je Au585Ag90Cu264Zn61, legura ,,bele“ boje je
Au585Ag65Cu277Zn16Pd57, kao i legura srebra Ag925Cu75. Dodatno legiranje
osnovnog trojnog Au-Ag-Cu sistema, urađeno je u cilju poboljšanja fizičko –
mehaničkih osobina, kao što su čvrstoća legure, obradivost, sposobnost legure za razne
oblike plastične deformacije, sposobnost za lemljenje i zavarivanje, itd. Kako u raznim
stadijumima proizvodnje nakita, posebno u toku termičke i/ili mehaničke obrade dolazi
do značajnih i višestrukih strukturnih promena, koje utiču i na boju materijala, a koje
još uvek nisu dovoljno istražene, deo istraživačke pažnje posvećen je i usklađivanju
istraživanih procesnih parametara sa očekivanom bojom ispitivanih legura.
Posebna pažnja, u eksperimentalnom delu rada, usmerena je na istraživanje režima
termičke obrade u procesu starenja, na temperaturama koje su niže od temperature
rekristalizacije, u cilju utvrđivanja uticaja temperature i vremena, u odabranom
ispitnom intervalu, na mikrostrukturu i fazne promene, koje su u direktnoj vezi sa
ojačavanjem istraživanih sistema legura. Pojava strukturnih promena u kristalnoj rešetki
legura, na granici faznih promena u čvrstom stanju (α(Au,Ag,Cu)↔α`(Ag,Au) + α“(Cu,Au)),
fenomen ,,uređeno-neuređeno“ (formiranje uređenih rešetki: AuCuI, AuCuII, Au3Cu i
AuCu3), pojava dvojnika žarenja, kao i drugih mikrostrukturnih promena, dovodi do
toga da se značajno poveća čvrstoća u ovim legurama. Pored navedenih promena,
takođe dolazi i do povećanja tvrdoće žarenjem na temperaturi starenja, usled pojave
precipitacije, kako po granicama zrna, tako i u samom zrnu, zajedno sa nagomilavanjem
i kočenjem dislokacija, koje su nastale hladnom deformacijom, i koje pokušavaju da se
oslobode, dovođenjem spoljne energije. Ojačavanje istraživanih legura u procesu
starenja praćeno je sistematskim ispitivanjem promene vrednosti tvrdoće, u odnosu na
početno stanje, kao i na stanje nakon izvršene rekristalizacije...
It takes knowledge of different parts of science to produce jewelery out of one piece of
pure gold, starting from metallurgy, physical chemistry, mechanical engineering,
through medicine, all to science of design and esthetical demands, always including the
history of art. From the point of view of metallurgy, in this paper some of very
important, but not enough examined aspects, that are connected to single phases of
production of jewelry of gold and silver alloys, were considered and experimentally
investigated.
The subject of this paper was directed to research, define and optimization of the most
important parameters that inflect on final properties and quality of multicomponent
aloys of Au-Ag-Cu system, in terms of investigation of relation: chemical composition
– thermal – processing – hardness – electrical conductivity. All of this demands
multidisciplinary approach to the problem of production of jewelry, especially, because
the jewelry fulfills the needs of a man of beautiful....
Three types of alloys were studied, according to law norms of the Republic of Serbia,
and needs of the market. Alloy of ,,yellow“ color is Au585Ag90Cu264Zn61, alloy of
,,white“ color is Au585Ag65Cu277Zn16Pd57, and silver alloy is Ag925Cu75. An
additional alloying of basic ternary system was performed in order to improve physical
– mechanical properties, such as strength of alloy, workability, ability of alloy to
different kinds of plastic deformation, ability to soldering and welding, etc. As in
different stages of jewelry production, especially during thermal and/or mechanic
processing significant and multiple structural changes occur, changes that inflect on
color of the material, and are not investigated enough; a part of this research was
dedicated to coordination of investigated processing parameters with expected color of
investigated alloys.
Special attention, during the experimental part of the paper, was directed on
investigation of regime thermal treatment in process of ageing, on temperatures below
the temperature of recristallization, in order to establish the inflection of temperature
and time, i chosen investigation interval, on microstructure and phase changes, that are
directly connected to age-hardening of investidated alloy`s systems. Occurrence of
structural changes in crystal lattice of alloys, on borders of phase changes in solid state
(α(Au,Ag,Cu) ↔ α`(Ag,Au) + α”(Cu,Au)), phenomena of ,,ordered – disordered“ (forming of
ordered lattices: AuCu I, AuCu II, Au3Cu and AuCu3), occurence of twining of
annealing as well as other micro structural changes, bring to significant increasement in
strength of this alloys. Beside these changes, there is also increasement in hardness by
annealing on temperature of ageing, due to phenomena of precipitation both on borders
of grains, and inside the grains, and also due to inhibition of dislocations, that now tend
to release by bringing in the external energy. Hardening of investigated alloys during the process of ageing was followed by systematic examination of change of hardness
value, related to initial state, and also to the state after the recristallization...