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1

Synthesis of Mg-based alloys with rare-earth element addition by means of mechanical alloying

Lesz Sabina, Hrapkowicz Bartłomiej, Gołombek Klaudiusz, Karolus Małgorzata, Janiak Patrycja

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2021

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Vol. 69, nr 5

art. no. e137586

EN

Magnesium-based alloys are widely used in the construction, automotive, aviation and medical industries. There are many parameters that can be modified during their synthesis in order to obtain an alloy with the desired microstructure and advantageous properties. Modifications to the chemical composition and parameters of the synthesis process are of key importance. In this work, an Mg-based alloy with a rare-earth element addition was synthesized by means of mechanical alloying (MA). The aim of this work was to study the effect of milling times on the Mg-based alloy with a rare-earth addition on its structure and microhardness. A powder mixture of pure elements was milled in a SPEX 8000D high energy shaker ball mill under an argon atmosphere using a stainless steel container and balls. The sample was mechanically alloyed at the following milling times: 3, 5, 8 and 13 h, with 0.5 h interruptions. The microstructure and hardness of samples were investigated. The Mg-based powder alloy was examined by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and using a Vickers microhardness test. The results showed that microhardness of the sample milled for 13 h was higher than that of those with milling time of 3, 5 and 8 h.

2

Mechanical alloying of Mg-Zn-Ca-Er alloy

Hrapkowicz Bartłomiej, Lesz Sabina, Kremzer Marek, Karolus Małgorzata, Pakieła Wojciech

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2021

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Vol. 69, nr 5

art. no. e137587

EN

Magnesium-based materials constitute promising alternatives for medical applications, due to their characteristics, such as good mechanical and biological properties. This opens many possibilities for biodegradable materials to be used as less-invasive options for treatment. Degradation is prompted by their chemical composition and microstructure. Both those aspects can be finely adjusted by means of proper manufacturing processes, such as mechanical alloying (MA). Furthermore, MA allows for alloying elements that would normally be really hard to mix due to their very different properties. Magnesium usually needs various alloying elements, which can further increase its characteristics. Alloying magnesium with rare earth elements is considered to greatly improve the aforementioned properties. Due to that fact, erbium was used as one of the alloying elements, alongside zinc and calcium, to obtain an Mg₆₄Zn₃₀Ca₄Er₁ alloy via mechanical alloying. The alloy was milled in the SPEX 8000 Dual Mixer/Mill high energy mill under an argon atmosphere for 8, 13, and 20 hours. It was assessed using X-ray diffraction, energy dispersive spectroscopy and granulometric analysis as well as by studying its hardness. The hardness values reached 232, 250, and 302 HV, respectively, which is closely related to their particle size. Average particle sizes were 15, 16, and 17 μm, respectively.

3

Non-conventional processing routes and applications of intermetallics

Novak P.

Mechanik

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2015

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R. 88, nr 2CD

93--99

EN

Intermetallics are materials offering wide variety of interesting properties, such as high hardness, high chemical resistance, shape memory or hydrogen storage ability. However, the synthesis and processing of intermetallic compounds by common metallurgical techniques is often very problematic. In this paper, the modern techniques involving non-conventional processes of powder metallurgy, reactive sintering and mechanical alloying, are presented. In the field of application, novel directions are linked – the use of intermetallic-based materials as surgical implants or tool materials.

PL

Materiały na osnowie faz intermetalicznych oferują szeroką gamę interesujących właściwości, takich jak wysoka twardość, wysoka odporność chemiczna, pamięć kształtu i zdolność do przechowywania wodoru. Jednakże synteza i wytwarzanie związków międzymetalicznych zwykłymi technikami metalurgicznymi jest często bardzo problematyczna. W niniejszej pracy zaprezentowano nowoczesne techniki obejmujące niekonwencjonalne procesy metalurgii proszków, spiekania reaktywnego i mechanicznego stopowania Wskazano nowe zastosowania materiałów na osnowie faz intermetalicznych, takie jak implanty chirurgiczne czy materiały narzędziowe.

4

Application of the high pressure torsion supported by mechanical alloying for the metal-graphene composites preparation

Czeppe T., Korznikova G., Ozga P., Lityńska-Dobrzyńska L., Socha R.

Mechanik

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2015

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R. 88, nr 2CD

147--157

EN

From the time when the method of a monolayer graphene preparation was published the scientific activity concerning the properties, production and application of this special form of carbon is very intensive. Graphene is two dimensional (2D) crystalline material, stable in a wide temperature range, possessing unusual electronic,electrical, thermal and mechanical properties. Graphene and the graphene oxide properties may be used in the range of the metal matrix composites, in which case graphene particles may improve electrical and thermal conductivity or/and strength of the material. The paper presents results of the studies concerning application of the high pressure torsion, one of the method of intensive deformation of metals to the powders consolidation to the homogenous composite metal-graphene structure. The aluminum and copper - graphene compositions were investigated. It was found that mechanical alloying as the preliminary step increased density and microhardness of the samples achieved by the High Pressure Torsion. As a result small, thin and round samples of composites and similar metallic samples not containing graphene, about 10 mm in diameter were achieved. The X-ray diffraction (XRD), transmission electron microscopy (ТЕМ), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were applied to study structure and analyze graphene content and atomic bonds. The Raman spectroscopy proved the presence of the multilayer graphene which could also be identified as the defected nano-graphitc as a component of the composite structure. In case of the Al-graphene composites small content of the aluminum carbides was detected as well. The metallic matrices of the samples revealed highly dispersed microstructures transmission electron microscopy show, in dependence on the number of rotations applied in the High Pressure Torsion process, leading to the increased plastic deformation of the consolidated material. The XPS method revealed increased amount of the carbon-metal and carbon- metal- oxygen atomic bonds in the case of the metal-graphene composites, suggesting partial transformation of the multilayer graphene in the graphene due to the high range of deformations applied.

PL

Praca przedstawia wyniki badań dotyczących próbek z proszku aluminium i kompozytów aluminium–grafen, wytworzonych w dwóch etapach: mechanicznej syntezy mieleniem i intensywnego odkształcenia metodą skręcania pod wysokim ciśnieniem. Wytworzono próbki w postaci okrągłej, o średnicy około 10 mm, charakteryzujące się znaczną jednorodnością mikrostruktury w przekroju. Zastosowanie wstępne mechanicznej syntezy podniosło mikrotwardość próbek i stopień kompresji. Dodatek grafenu nie miał wpływu na te parametry. Przeprowadzono badania metodami transmisyjnej mikroskopii elektronowej, spektroskopii Ramana i spektroskopii fotoelektronów XPS. Wyniki transmisyjnej mikroskopii elektronowej i spektroskopii Ramana wskazują na równomierne rozłożenie cząstek grafenu na powierzchni ziaren matrycy. Zwiększenie odkształcenia ścinającego w metodzie skręcania pod wysokim ciśnieniem prowadzi do silniejszego rozdrobnienia struktury matrycy i cząstek grafenu. Jak wynika ze spektroskopii Ramana, wprowadzony grafen może być zakwalifikowany jako grafen wielowarstwowy, zdefektowany. Konsolidacja przy pomocy intensywnego odkształcenia skręcaniem pod wysokim ciśnieniem zwiększa zdefektowanie i dyspersję grafenu oraz prawdopodobnie zwiększa zawartość grafenu o małej ilości warstw. Metoda XPS wskazuje na powstawanie wiązań atomowych węgiel–glin i zmniejszenie udziału wiązań węgiel-węgiel i glin-glin. Stwierdzono także tworzenie się niewielkiej ilości węglików aluminium.

5

Properties Of MgB2/Ga Composites Prepared By Mechanical Alloying

Yoon K., Ahn J.-H.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 2B

1271--1274

EN

In this study, we examined the effect of Ga-doping and mechanical alloying in MgB2 on microstructural and phase evolution. A comparison was made between in-situ and ex-situ processed Mg-B-Ga samples. Densification was markedly improved by ex-situ sintering of ball-milled MgB2+Ga. The Ga-doping and ball-milling prior to sintering resulted in the formation of impurity phases such as MgO, Ga5Mg2 and Ga2O3. Lattice parameter of MgB2 increased with increasing ball-milling duration as well as by Ga-doping.

6

Infiltration Behavior Of Mechanical Alloyed 75 wt% Cu-25 wt% WC Powders Into Porous WC Compacts

Şelte A., Özkal B.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 2B

1565--1568

EN

In this work infiltration behavior of mechanical alloyed 75 wt% Cu – 25 wt% WC powders into porous WC compacts were studied. Owing to their ductile nature, initial Cu powders were directly added to mechanical alloying batch. On the other hand initial WC powders were high energy milled prior to mechanical alloying. Contact infiltration method was selected for densification and compacts prepared from processed powders were infiltrated into porous WC bodies. After infiltration, samples were characterized via X-Ray diffraction studies and microstructural evaluation of the samples was carried out via scanning electron microscopy observations. Based on the lack of solubility between WC and Cu it was possible to keep fine WC particles in Cu melt since solution reprecipitation controlled densification is hindered. Also microstructural characterizations via scanning electron microscopy confirmed that the transport of fine WC fraction from infiltrant to porous WC skeleton can be carried out via Cu melt flow during infiltration.

7

Effect Of Hot Pressing On The Electrochemical Properties Of Ti-Ni Alloy

Balcerzak M., Jurczyk M.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 2B

1335--1340

EN

Ti2Ni alloy pellets were produced by mechanical alloying and hot pressing at 750°C for 0.5 h in vacuum. X-ray diffraction analysis showed that, after 8 h of milling, a starting mixture of elements mostly decomposed into an amorphous phase. Obtained powders and flakes have cleavage fracture morphology with huge number of dimples with different sizes. Hot pressing of materials caused formation of Ti2Ni main phase. Porosity of pellets strongly depended on size of agglomerates and pressure of pressing. Ti2Ni pellets were used as negative electrodes for Ni-MHx batteries. Maximum measured discharge capacity of studied materials was 220 mAh/g. Electrochemical properties resulted from size of agglomerates, degree of oxidation and pressure of pressing.

8

An Experimental Study Of Aluminum Alloy Matrix Composite Reinforced SiC Made By Hot Pressing Method

Suśniak M., Karwan-Baczewska J., Dutkiewicz J., Actis Grande M., Rosso M.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 2B

1523--1527

EN

The present work investigates the possibility of using powder metallurgy processing for producing a metal matrix composite. Materials were prepared from AlSi5Cu2 chips with reinforcement of 10, 15, 20 wt. % silicon carbide. Aluminum alloy chips were milled with SiC powder in a high-energy ball mill by 40 hours. Mechanical alloying process lead to obtain an uniform distribution of hard SiC particles in the metallic matrix and refine the grain size. The consolidation of composite powders was performed by vacuum hot pressing at 450°C, under pressure of 600 MPa by 10 min. The results shows that the addition of SiC particles has a substantial influence on the microstructure and mechanical properties of composite powder as well as consolidated material. Hot pressing is an effective consolidation method which leads to obtain dense AlSi5Cu2/SiC composite with homogeneous structure and advanced mechanical properties.

9

Fabrication of Open Cell Fe-10%Al Foam by Space-Holder Technique

Golabgir M. H., Ebrahimi-Kahrizsangi R., Torabi O., Saatchi S.

Archives of Metallurgy and Materials

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2014

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Vol. 59, iss. 1

41--45

EN

In this paper, fabrication of open-celled porous Fe-10%A1 foam by space-holder technique in which NaCl powder and polyester resin were utilized as space holder and binder respectively to generate 30-80% porosities was studied. FeAl solid solution was prepared via mechanical alloying method after 25 h high energy milling process. The results indicate that the size and shapes of the pores are determined by the size and shapes of NaCl particles. Also, when compaction pressure was in the range of 70-150 MPa and the sintering process was performed at temperature around 1100°C, the samples had the best quality. Microstructure observations show the pore size was in the range of 200-500 μm.

PL

W niniejszej pracy badano wytwarzanie techniką wypełniacza przestrzeni piany Fe-10%Al o otwartej porowatości, w której proszek NaCl i Żywicę poliestrową wykorzystano odpowiednio w roli wypełniacza porów i spoiwa do wytworzenia piany o 30-80% porowatości. Roztwór stały FeAl został wytworzony poprzez mechaniczne stopowanie przez 25 h w trakcie wysokoenergetycznego mielenia. Wyniki wskazują, że rozmiar i kształt porów determinowany jest przez wielkość i kształt cząstek NaCl. Ponadto, gdy ciśnienie prasowania było w zakresie 70-150 MPa a proces spiekania prowadzono w temperaturze około 1100°C. próbki miały najwyższą jakość. Obserwacje mikrostruktury wykazały, że rozmiar porów mieścił się w zakresie 200-500 μm.

10

Wytwarzanie materiałów termoelektrycznych na osnowie związku Bi2Te3 techniką spiekania plazmowego

Wrona A., Staszewski M., Mazur J., Kamińska M., Lis M., Osadnik M., Bilewska K.

Rudy i Metale Nieżelazne

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2012

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R. 57, nr 11

765-770

PL

Analizowano możliwość otrzymywania związków międzymetalicznych Bi2Te3, Bi0,4Sb1,6Te3 i Bi2Te2,95Se0,05 za pomocą metody łączącej mechaniczną syntezę i iskrowe spiekanie plazmowe. Stwierdzono, że już samo mechaniczne stopowanie umożliwia otrzymanie związków Bi2Te3 i Bi2Te2,95Se0,05 w czystej postaci. W stopie o składzie Bi0,4Sb1,6Te3 dopiero spiekanie plazmowe powoduje pełne przereagowanie stopowanych metali. Konsolidacja otrzymanych proszków, metodą spiekania plazmowego w określonych warunkach, umożliwia zachowanie ich struktury nanokrystalicznej, uzyskanej podczas mechanicznego stopowania.

EN

A possibility of synthesis of Bi2Te3, Bi0.4Sb1.6Te3 and Bi2Te2.95Se0.05 intermetallic compounds through a method that combines mechanical alloying with spark plasma sintering was analyzed. It has been found that mechanical alloying already enables obtaining pure Bi2Te3 and Bi2Te2.95Se0.05 compounds. However, for Bi0.4Sb1.6Te3 alloy spark plasma sintering is necessary to complete reaction between mechanically alloyed metals. Additionally consolidation of mechanically alloyed powders under specific conditions using spark plasma sintering preserves their nanocrystalline structure obtained during mechanical alloying.

11

Influence of the mechanical alloying process on the sintering behaviour of Astaloy CrM powder mixture with silicon carbide addition

Hebda M., Gądek S., Kazior J.

Archives of Metallurgy and Materials

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2012

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Vol. 57, iss. 3

733-743

EN

Due to an excellent combination of toughness and strength, bainitic-austenitic dual phase steels with silicon addition have many applications in the industry. However, silicon has a high affinity to oxygen and, therefore, its introduction to the alloy is problematic during the classical sintering processes of mixing powders. Mechanical alloying (MA) offers one of the most attractive alternatives to the introduction of silicon to Astaloy CrM powders. The aim of the present study was to determine the influence of the MA process on changes in particle size distribution, work hardening and sintering behaviour of the investigated powder mixture - Astaloy CrM powder with the addition of 2 wt.% stearic acid and 2 wt.% silicon carbide alloyed under different conditions. The practical aspect of this study was to develop and apply a common and inexpensive method of die-pressing to compact a powder mixture prepared by the MA process.

PL

Dwufazowe stale bainityczno-austenityczne ze względu na swoje właściwości wytrzymałościowe i plastyczne maja coraz szersze zastosowanie w przemyśle. Jednakże wprowadzanie do składu mieszanek dodatku krzemu nastręcza wiele problemów technologicznych podczas klasycznego spiekania materiałów proszkowych m.in. poprzez duże powinowactwo tego pierwiastku do tlenu. Proces mechanicznego stopowania oferuje jedno z alternatywnych rozwiązań wprowadzenia krzemu do niskostopowych proszków Astaloy CrM. W pracy przedstawiono wyniki badan wpływu procesu mechanicznego stopowania na zmiany wielkości cząstek proszku, ich utwardzenie oraz efekty zachodzące podczas spiekania mieszanek: Astaloy CrM z dodatkiem 2% wg kwasu stearynowego.

12

Structure and properties of sintered tool gradient materials

Dobrzański L. A., Dołżańska B.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 43, nr 2

711--733

EN

Purpose: The main objective of the presented is to elaborate the fabrication technology of novel sintered tool gradient materials on the basis of hard wolfram carbide phase with cobalt binding phase, and to carry out research studies on the structure and properties of the newly elaborated sintered tool gradient materials. Design/methodology/approach: The following research studies have been carried out to elaborate a new group of sintered tool gradient materials, wolfram carbide with cobalt matrix, to elaborate their fabrication technology and to determine their structure and properties: a fabrication technology of mixtures and the formation technology of wolfram carbide gradient materials with cobalt matrix WC-Co was applied and elaborated; sintering conditions were selected experimentally: time, temperature and sintering atmosphere as well as isostatic condensation, ensuring the best structure and properties; phase and chemical composition of the sintered gradient WC-Co materials was determined using EDX, EBSD methods and qualitative X-ray analysis; the structure of sintered gradient WC-Co materials was investigated using scanning microscopy and transmission electron microscopy; mechanical and physical properties of sintered gradient WC-Co materials was determined: porosity, density, hardness, resistance to abrasive wear, resistance to brittle cracking. Findings: The presented research results confirm that the newly elaborated technology of powder metallurgy, which consists in sequential coating of the moulding with layers having the increasing content of carbides and decreasing concentration of cobalt, and then sintering such a compact, ensures the acquisition of the required structure and properties, including the resistance to cracking and abrasive wear of tool gradient materials, due to earned high hardness and resistance to abrasive wear on the surface as well as high resistance to cracking in the core of the materials fabricated in such a way. Practical implications: The material presented in this paper is characterized by very high hardness of the surface and relative ductility of the core. TGM with smooth changes of the cobalt phase in the material. Originality/value: The obtained results show the possibility to manufacture TGMs on the basis of different portions of cobalt reinforced with hard ceramics particles in order to improve the abrasive resistance and ductility of tool cutting materials.

13

Kompozyt amorficzno-ceramiczny na osnowie stopu niklu umocniony Al2O3 wytworzony metodą syntezy mechanicznej i konsolidacji proszku

Oleszak D., Kulik T., Kolesnikov D.

Kompozyty

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2007

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R. 7, nr 4

195-199

PL

Podjęto próbę wytworzenia kompozytu metaliczno-ceramicznego, w którym osnową jest amorficzny stop na bazie niklu Ni59Zr20Ti16Si5, a umacniającą fazą ceramiczną - korund. Kompozyt uzyskano poprzez zagęszczanie proszków metodą prasowania izostatycznego. Stopowe proszki amorficzne na bazie niklu wytworzono metodą mechanicznej syntezy. Do tej mieszaniny dodano w końcowej fazie procesu mielenia proszku korundu (20% obj.). Wykorzystano przy tym dwa rodzaje tego proszku: standardowy mikrometryczny (50 žm) oraz nanoproszek (80 nm). Poddana mieleniu mieszanina proszków wyjściowych uległa amorfizacji. Stwierdzono, że dodatek proszku korundu obniża stabilność termiczną stopu amorficznego. Przejawia się to obniżeniem temperatury początku krystalizacji fazy amorficznej. W przypadku proszku mikrometrycznego przesunięcie to jest stosunkowo niewielkie (kilka stopni), natomiast dla nanoproszku sięga 50°C. Związane jest to prawdopodobnie z ułatwionym zarodkowaniem fazy krystalicznej na nanocząstkach korundu. Podczas procesu prasowania izostatycznego (1,5 GPa, 0,5 h, 440 i 480°C) nastąpiła częściowa krystalizacja amorficznej osnowy kompozytu, co potwierdziły badania rentgenowskie i kalorymetryczne. Na podstawie dyfrakcyjnych badań rentgenowskich można stwierdzić, że otrzymane produkty krystalizacji wykazywały nanokrystaliczny charakter, jednakże dokładna ich charakterystyka wymaga przeprowadzenia dalszych badań (TEM), a proces konsolidacji - optymalizacji.

EN

An attempt was made to obtain bulk metallic glasses composite by mechanical alloying followed by powder compaction. Ni-based amorphous matrix was fabricated by milling of a mixture of pure crystalline elements. Two types of Al2O3 powders were added (20 vol. %) as the ceramic phase: micrometer in size (50 žm) and nanopowder (80 nm). Mechanical alloying resulted in a full amorphization of the alloy. The addition of ceramic powder influenced the thermal stability of the amorphous phase. Especially in the case of nanopowders, the crystallization temperature of the first crystallization stage of amorphous phase was decreased by about 50°C. The applied parameters of isostatic pressing (1.5 GPa, 0.5 h, 440 and 480°C) resulted in partial crystallization of the alloy. It was verified by XRD and DSC studies. The quality of the compaction was checked by optical microscopy observations, revealing some micropores.

14

Wpływ wolframu, wanadu oraz chromu na właściwości wytwarzanych mechanicznie stopów na osnowie fazy gamma-TiAl

Dymek S., Wróbel M., Blicharski M.

Inżynieria Materiałowa

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2004

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R. XXV, nr 6

869-873

PL

W pracy wytworzono i badano stop o składzie chemicznym (% at.) TiAl45W5. Syntezę tego stopu przeprowadzono metodą mechanicznego stopowania mieszaniny proszków stopu TiAl oraz czystego wolframu. Proces stopowania wykonano w laboratoryjnym atritorze typu Szegvari w atmosferze argonu. Komorę roboczą młyna chłodzono ciekłym azotem lub wodą. Dokonano również porównania syntezy tego stopu z syntezą stopów TiAl45Cr5 i TiAl45V5 wytworzonych z czystych składników przy tych samych parametrach procesu. Stwierdzono, że proces syntezy z użyciem proszku stopowego TiAl oraz W zasadniczo różni się od procesu prowadzonego z udziałem czystych składników. W odróżnieniu od chromu i wanadu, wolfram w małym stopniu przechodzi do roztworu stałego, podczas mechanicznego stopowania materiałów na osnowie TiAl. Po procesie mechanicznego stopowania proszki konsolidowano przez prasowanie na gorąco. W stopie Ti45Al5W główną fazą dyspersyjną jest wolfram. W stopach Ti45Al5V oraz Ti45Al5Cr główną fazą dyspersyjną są tlenki aluminium. Twardość stopu zawierającego wolfram jest mniejsza niż stopów zawierających chrom lub wanad. Największą odporność na pękanie wykazał stop z wolframem. Dodatek Cr lub V pogarsza odporność na pękanie. Stopy z wanadem miały istotnie mniejszą wartość K(Ic) niż stop z chromem. Odporność na pękanie można poprawić zastępując prasowanie przez wyciskanie na gorąco. Mimo, że stop Ti45Al5W posiada największą gęstość (o ok. 11 % większa niż gęstość stopu Ti Al48), to i tak jest ona istotnie mniejsza od gęstości konkurencyjnych materiałów (nadstopy).

EN

An alloy with chemical composition of TiAl45W5 (% at.) was synthesized by mechanical alloying in a Szegvari-type attritor. The prealloyed TiAl and pure elemental W powders were used for the synthesis. The process was carried out in an argon atmosphere. The milling chamber was cooled during the process by liquid nitrogen or water. The synthesis process of this alloy was compared to the synthesis of formerly produced alloys TiAl45Cr5 and TiAl45V5 processed from elemental powders at the same conditions of milling. It was found that the synthesis carried out with the use of prealloyed powders substantially differed from synthesis of pure elemental powders. Unlike Cr or V the tungsten only slightly dissolved in TiAl. After the mechanical alloying process the powders were compacted by hot pressing. In the compacted TiAl45W5 alloy the dispersed phase was constituted mainly by tungsten while in TiAl45Cr5 and TiAl45V5 alloys the dispersed phase was identified as Al2O3 oxide particles. However, the hardness of the alloy strengthened by W particles was lower than the hardness of the two other alloys but exhibited the highest fracture toughness. The addition of Cr and V lower fracture toughness of the TiAl alloy. The effect of V was stronger in this respect. However, the fracture toughness could be increased by replacing the method of consolidation from hot pressing to hot extrusion. The TiAl45W alloy has greater density (about 11 % greater than that of TiAl alloy) but regardless of this fact its density is much lower than that of competitive materials (superalloys).

15

Synthesis and structure changes during mechanical alloying of Nb22Ti15Al alloy

Rozmus M., Blicharski M., Dymek S.

Inżynieria Materiałowa

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2004

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R. XXV, nr 3

490-492

EN

The main aim of this work was an attempt to employ mechanical alloying to synthesise an intermetallic-based Nb22Ti15Al alloy which would exhibited better mechanical properties than its counterparts produced by other methods and to investigate structure changes during mechanical alloying and during annealing and consolidation. The material investigated in this study was produced by mechanical alloying of pure elemental powders of Nb, Ti and Al. The morphology and structure changes during milling, annealing and consolidation were examined using a scanning electron microscope and the X-ray diffractometer with CoKalpha radiation. The powder was also characterized by microhardness measurements. The mechanical alloying resulted in the formation of Nb solid solution. Intermetallic phases appeared during annealing and consolidation of powder. Influence of consoldidation temperature on the phase content was established. The increase in consolidation temperature resulted in the nucleation of a brittle Nb2Al phase. It has been shown that mechanical alloying followed by hot pressing is a viable processing route for intermetallics Nb-Ti-Al.

PL

Głównym celem pracy było zastosowanie mechanicznego stopowania do wytwarzania stopu Nb22Ti15Al oraz badanie zmian zarówno morfologicznych jak i strukturalnych zachodzących podczas procesu wytwarzania, jak również w wyniku wyżarzania i konsolidacji badanego materiału. W tym celu mieszaninę proszków czystych metali Nb, Ti i Al poddano mechanicznej syntezie w wysokoenergetycznym młynie typu attritor, a następnie morfologiczne i strukturalne zmiany zachodzące podczas mielenia proszku, jak również w wyniku wyżarzania i konsolidacji badano za pomocą skaningowej mikroskopii elektronowej oraz metodą rentgenowskiej analizy fazowej. Próbki proszku po kolejnych etapach mielenia scharakteryzowano również przez pomiar mikrotwardości metodą Vickersa. Wyżarzony w temperaturze 1000 °C proszek po mechanicznym stopowaniu składał się z roztworu stałego na osnowie niobu i fazy Nb3Al. Materiał po konsolidacji przez prasowanie na gorąco w temperaturze 1200 °C przez 3 h składał się z roztworu stałego na osnowie niobu oraz faz Nb3Al i Ti3Al, natomiast w wyniku konsolidacji w temperaturze 1300°C przez 3 h faza Ti3Al została zastąpiona kruchą fazą Nb2Al.

16

Mechanical alloying of Mg-based metallic glasses and nanostructured composites.

Eckert J.

Archives of Materials Science

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2004

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Vol. 25, nr 4

321-331

EN

Mg55Y15Cu33-based metallic glass matrix composites are produced by mechanical alloying of elementar powder mixtures containing up to 3- vol. % of Y2O3 particles. Comparison with the particle-free metallic glass reveals that the nanosized second phase oxide particles do not significantly affect the glass-forming ability upon mechanical alloying despite some limited particle dissolution. A supercooled liquid region with an extension of about 50 K can be maintained in the processes of the oxides. The distinct viscosity decrease in the supercooled liquid regime allows for consolidation of powders into bulk samples by uniaxial hot pressing. The Y2O3 additions increase the mechanical strength of the composites compared to the Mg55Y15Cu33 metallic glass.

17

Mechanical alloying and thermal stability of the Co-Al alloys.

Tretjakov K.V., Portnoi V.K., Fadeeva V. I.

Archives of Materials Science

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2004

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Vol. 25, nr 4

547-552

EN

The cobalt rich Co-Al alloys prepared by mechanical alloying (MA) have been investigated using X-ray analysis and differential scanning calorymetry. At the initial stage of MA fcc Co high-temperature modification transforms to the hcp Co low-temperature one. The prolongation of milling leads to reverse transformation Co (hcp) -> Co fcc (al) solid solution formation. The structural transformation of Co under ball milling is closely related to the amount of stacking faults accumulated in both modifications of Co during milling. Al dissolves only in fcc Co and increases its stability. Even small amount of Al (3 at. %) stabilizes the stacking faults in hcp Co and accelerates structural transformation to fcc modification. The amount of fcc Co (Al) solid solution increases with the milling time and the milling energy. MA of Co - 15-25 at. % Al powder mixtures results in CoAl intermetallic and fcc Co(Al) solid solution formation at the intermediate stage of the synthesis. The intermatallic phase is fractured by long term milling. MA of Co - 50 at. % powders leads to single-phase CoAl intermtallic formation. The thermal tratment at 720 degrees C of the alloys sinthesized by MA leads to decomposition of the solid solution into the following phases Co fcc (Al), B2 CoAl and Co3Al metastable phase (type L12). This metastable phase decomposes at higher temperature.

18

Influence of milling time on the mechanism of phase structure formation in mechanically alloyed Nd-Fe-B magnets.

Kaszuwara W., Leonowicz M.

Archives of Materials Science

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2004

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Vol. 25, nr 4

523-529

EN

Mechanical alloying is one of the major methods for the processing of nanocrystalline Nd-Fe-B alloys. Long-time milling of elementary powders leads to formation of phase structure consisting of nanocrystalline iron particles embedded in an amorphous matrix. Synthesis of the hard magnetic Nd2Fe14B phase occurs in the course of low-temperature diffusion anealing of the milled material. Milling time appears to be one of the crucial parameters, determining the final phase structure and the material properties. The DSC and Moessbauer spectroscopy studies showed that the milling time affects the mechanism of phase formation. The materials obtained with short milling times contain substantial amount of the Nd2Fe17 phase. One can conclude that the Nd2Fe14B phase is formed by transformation of the Nd2Fe17 phase accompanied by decomposition of the Fe2B phase. The degree to which the transformation occurs is controlled by the milling time. One can neither exclude the apperance of the liquid phase during annealing of the material within a short milling time. Keeping other processing parameters constant, the milling time also affects the microstructure of magnets, especially the distribution of the grain size. The mean grain size decreases substantially with extension of the milling time.

19

Mechaniczna synteza i prasowanie na gorąco stopów na osnowie gama-TiAl.

Dutkiewicz J., Maziarz W.

Inżynieria Materiałowa

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2001

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R. XXII, nr 1

32-37

PL

Stop podwójny na osnowie fazy gama-TiAl o składzie chemicznym Ti-48Al oraz potrójne Ti-48,4Al-4,1Mn i Ti45,4Al-10Mn (liczby przed symbolem pierwiastka oznaczają % at.) poddano mechanicznej syntezie (MS) w wysokoenergetycznym młynie planetarnym typu Fritsch Pulverisette P5/4. MS przez okres 40 godzin spowodowała rozdrobnienie wyjściowych cząstek proszków do wielkości średniej około 8 mm oraz ujednorodnienie ich kształtu. Mechanizm rozdrabniania wieloskładnikowych cząstek oparty był na pracy utwardzenia oraz pękaniu w miejscach wzbogaconych w tytan. Dodatek manganu tylko w pierwszych etapach procesu wpływał na strukturę cząstek, powiększając ich wielkość poprzez lokowanie się w plastycznej osnowie aluminiowej. Badania przy użyciu dyfrakcji promieni rentgenowskich wykazały, że we wszystkich stopach nastąpiło utworzenie struktury amorficznej oraz roztworu stałego typu alfa-Ti(Al) oraz obserwowano tylko częściową rozpuszczalność manganu. Stosując metodę dopasowania stwierdzono, że względny udział fazy amorficznej po 40 godzianch mielenia w stopie Ti48Al wynosił 70%, podczas gdy w stopach Ti-48,4Al-4,1Mn i Ti-45,4Al-10Mn odpowiednio 72 i 78%. Prasowanie na gorąco proszków po procesie MS w temperaturze 1000 stopni Celsjusza pod ciśnieniem 35 MPa prowadziło do uzyskania materiałów litych o gęstości od 95-98% gęstości teoretycznej. Mikrostruktura próbek składała się z trzech oddzielnych stref różniących się morfologią i składem chemicznym, spowodowane to było dyfuzją węgla od grafitowej matrycy do próbki i tworzeniu TiC na jej powierzchni zewnętrznej. Strefy różniły się również porowatością, która malała w kierunku osi próbki. Wyżarzanie w próżni sprasowanych oraz dodatkowo obrobionych mechanicznie w celu zlikwidowania budowy strefowej w temperaturze 1300 stopni Celsjusza (stop podwójny) oraz 1250 stopni Celsjusza (stopy potrójne) spowodowało powstawanie struktur wielofazowych o średniej wielkości ziaren około 10 mm. W stopie podwójnym Ti-48Al występuje płytkowa dwufazowa struktura alfa2+gama(Ti3Al+TiAl) oraz drobne wydzielenia roztworu stałego alfa-Ti(Al). W stopach z dodatkiem manganu również przeważającą jest faza gama-TiAl, a dodatkowo występowały fazy alfa2-Ti3Al, Ti9Al23 oraz faza typu Lavesa Al17Mn50Ti33.

EN

The binary and ternary gamma-TiAl phase based alloys i.e. Ti-48Al., Ti-48.4Al-4.1Mn and Ti-45.4Al-10Mn alloys (in at. %) were mechanically alloyed (MA) in high energetic mill Fritsch Pulverisette P5/4. After 40 hours of milling the refinement of initial powder particle down to 8 micrometres and change of to close to spherical shape was observed. The refinement mechanism of multicomponent particles is based on the work hardening and fracture in places locally enriched in titanium. The addition of manganese increases the mean particle size in the first period of milling, as compare to binary Ti-48Al powder due to location of manganese particle in ductile aluminium matrix. The X-ray diffraction of these alloys showed that 40 hours of MA produces a mixture of amorphous and crystalline a-Ti(Al) solid solution phases containing manganese. The profile fitting procedure for quantitative analyse of diffraction curves showed that a fraction of the amorphous phase in powders was 70% in Ti-48Al alloy, 72% in Ti-48.4Al-4.1Mn and 78% in Ti-45.4Al-10Mn after 40 hours of milling. Hot pressing consolidation of these powders at 1000 degrees centigrade under 35MPa caused their densification up to 95-98% of theoretical density. In hot pressed samples three zones of different structure and phase composition were observed, due to the effect of carbon diffusion from the mould, causing TiC formation in the outer zone. The zones differ also in amount of pores, which decrease toward the centre of sample. The vacuum annealing at 1300 degrees centigrade (binary alloy) and at 1250 degrees centigrade (ternary alloys) of hot pressed samples with removed surface zones caused formation of multiphase structures with average grain size of about 10 mm. The binary Ti-48Al was characterized by two phase layered alpha2+gamma(Ti3Al+TiAl) structure and fine precipitates of alpha-Ti(Al) solid solution. In ternary alloys gamma-TiAl phase exists as a matrix and additional alpha2-Ti3Al, Ti9Al23 and Al17Mn50Ti33 phases were observed.