Kovinsko-keramični material z infiltrirano magnezijevo zlitino

doktorska disertacija

Matej Steinacher (Author), Franc Zupanič (Mentor), Primož Mrvar (Co-mentor)

Abstract

V tem delu je obravnavan kovinsko-keramični material z infiltrirano magnezijevo zlitino (kompozit IPC; ang. interpenetrating phase composite). Preiskovani kompozit IPC je bil izdelan s postopkom gravitacijskega kokilnega litja, karakteriziran s svetlobno mikroskopijo, vrstično in presevno elektronsko mikroskopijo, energijsko disperzijsko spektroskopijo in rentgensko difrakcijo ter bil mehansko preiskan. Osnova kompozita, magnezijeva zlitina AE44, ki je vsebovala 4,94 mas. % Al in 4,42 mas. % kovin redkih zemelj (RE), je bila sestavljena iz primarnih kristalov večkomponentne trdne raztopine Ž-Mg in intermetalnih faz Al11RE3, Al2RE in Al10RE2Mn7. Utrjevalna sestavina kompozita, keramična pena, je bila sestavljena iz Ž-Al2O3, Ž-SiC, Ž-SiC in SiO2. Keramična pena je imela odprto primarno in večinoma zaprto sekundarno poroznost. Pri litju je talina infiltrirala v primarne pore, v sekundarne pore pa se je delno infiltrirala, delno pa penetrirala skozi mostičke keramične pene. V mejnih območjih med zlitino AE44 in keramično peno se je pojavila močna reakcija, ki je vplivala na mikrostrukturo nastalega kompozita IPC, zato je bilo največ dela usmerjenega v natančno opredelitev mehanizmov in kinetike kemijskih reakcij v mejnih območjih. V ta namen so bili izvedeni poskusi litja z različnimi parametri, modelni preskusi interakcij tudi s kompaktno keramiko ter teoretični študij termodinamskih reakcij. Glavni reakcijski produkti v mejnih območjih AE44 - keramična pena inv penetriranih mostičkih keramične pene so bili MgO, AlSiRE in AlMgSiRE. Kot prvi je nastal MgO z redukcijo SiO2 in Al2O3 z magnezijem. Nato je na MgO nastala faza AlSiRE, na kateri je kasneje epitaksialno kristalizirala faza AlMgSiRE, katere delež se je z daljšim reakcijskim časom povečeval. Z mikrokemijsko analizo je bila opredeljena njuna kemijska sestava, dognano pa je bilo tudi, da imata fazi tetragonalno kristalno strukturo s povsem jasno medsebojno kristalografsko orientacijo. Ugotovljeno je bilo, da fazi AlSiRE in AlMgSiRE ne ustrezata nobeni znani fazi. Kompozit IPC je imel v vseh preiskanih stanjih večjo napetost tečenja in modul elastičnosti ter manjšo upogibno in tlačno trdnost kot zlitina AE44. Faza AlMgSiRE je imela manjšo trdoto in manjši modul elastičnosti od faze AlSiRE.

Keywords

magnezijeva zlitina;keramična pena;mejno območje;reakcijski produkti;

Data

Language:	Slovenian
Year of publishing:	2013
Typology:	2.08 - Doctoral Dissertation
Organization:	UM FS - Faculty of Mechanical Engineering
Publisher:	M. Steinacher]
UDC:	666.789:620.1/.2(043.3)
COBISS:	17142038
Views:	2039
Downloads:	162
Average score:	0 (0 votes)
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Other data

Secondary language:	English
Secondary title:	METAL-CERAMIC MATERIAL WITH AN INFILTRATED MAGNESIUM ALLOY
Secondary abstract:	This work presents the development of a metal-ceramic material with an infiltrated magnesium alloy (interpenetrating phase composite; IPC). The IPC was manufactured by gravity permanent mould casting, characterized by optical microscopy, scanning and transmission electron microscopy, energy dispersive spectroscopy, energy dispersive X-ray analysis, and it was mechanically tested. The matrix, an AE44 magnesium alloy that contained 4.94 wt. % Al and 4.42 wt. % rare-earth elements (RE) was composed of Ž-Mg primary crystals of amulti-component solid solution, Al11RE3, Al2RE, and Al10RE2Mn7 intermetallic phases. The reinforcement, ceramic foam was composed of Ž-Al2O3, Ž-SiC, Ž-SiC, and SiO2. The ceramic foam had open primary and mostly closed secondaryporosity. Upon casting, the melt infiltrated into the primary pore and it partly infiltrated and partly penetrated through the struts of ceramic foam into the secondary pore. Strong reaction appeared at the interfaces between the AE44 alloy and the ceramic foam and influenced the microstructure of the IPC. Therefore, the majority of work was oriented towards defining the mechanisms and kinetics of chemical reactions at the interfaces. Experimental castings using different parameters, model experiments of interactions also with compact ceramics, and a theoretical study of the thermodynamic reactions were made for this purpose. The main reaction products at the AE44 - ceramic foam interfaces and in the penetrated struts of ceramic foam were MgO, AlSiRE,and AlMgSiRE. MgO was formed first with a reduction of SiO2 and Al2O3 by magnesium. Then AlSiRE was formed on the MgO. Later AlMgSiRE was epitaxially crystallized on AlSiRE and its content was increased by increasingthe reaction times. Their chemical composition was defined using microchemical analysis and it was established that the phases had tetragonal crystal structures with clear mutual crystallographic orientation. It was discovered that AlSiRE and AlMgSiRE did not correspond to any known phase. TheIPC had, for all the investigated states, a higher yield stress and Young'smodulus and a lower bending and compression strength in comparison to the AE44 alloy. The AlMgSiRE phase had a lower hardness and Young's modulus than the AlSiRE phase.
Secondary keywords:	magnesium alloy;ceramic foam;composite;interface;reaction product;Kompoziti;Disertacije;
URN:	URN:SI:UM:
Type (COBISS):	Dissertation
Thesis comment:	Univ. v Mariboru, Fak. za strojništvo
Pages:	X, 116 f.
ID:	8727036