Structure and properties of Al–Mg mechanical alloys

2003 ◽  
Vol 18 (8) ◽  
pp. 1827-1836 ◽  
Author(s):  
Mirko Schoenitz ◽  
Edward L. Dreizin
Keyword(s):  
Solid Solution ◽  
Energetic Materials ◽  
Amorphous Material ◽  
Bulk Composition ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Β Phase ◽  
Α Phase ◽  
Diffraction Microscopy

Mechanically alloys in the Al–Mg binary system in the range of 5–50 at.% Mg were produced for prospective use as metallic additives for propellants and explosives. Structure and composition of the alloys were characterized by x-ray diffraction microscopy (XRD) and scanning electron microscopy. The mechanical alloys consisted of a supersaturated solid solution of Mg in the α aluminum phase, γ phase (Al12Mg17), and additional amorphous material. The strongest supersaturation of Mg in the α phase (20.8%) was observed for bulk Mg concentrations up to 40%. At 30% Mg, the γ phase formed in quantities detectable by XRD; it became the dominating phase for higher Mg concentrations. No β phase (Al3Mg2) was detected in the mechanical alloys. The observed Al solid solution generally had a lower Mg concentration than the bulk composition. Thermal stability and structural transitions were investigated by differential scanning calorimetry. Several exothermic transitions, attributed to the crystallization of β and γ phases were observed. The present work provides the experimental basis for the development of detailed combustion and ignition models for these novel energetic materials.

Investigation on β-Polypropylene/Talc Composites

2012 ◽  
Vol 182-183 ◽  
pp. 259-264
Author(s):  
Jia Wei Duan ◽  
Qiang Dou
Keyword(s):  
Polarized Light ◽  
Nucleating Agent ◽  
Mechanical Tests ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Melt Compounding ◽  
Β Phase ◽  
Α Phase ◽  
Melting And Crystallization

In this study polypropylene (PP) composites containing β-nucleating agent (NT-C) and talc filler were prepared by melt compounding. The melting and crystallization behavior, morphology and mechanical properties of the composites were studied by means of differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD), polarized light microscopy (PLM) and mechanical tests. The results indicate that talc suppresses the formation of β phase, but promotes the formation of α phase. The Izod notched impact strength and tensile strength of β-PP/talc composites are superior to those of PP/talc composites, indicating an outstanding balance of stiffness and toughness of β-PP/talc composites.

Mechanical Alloying Behavior in the Nb-Si, Ta-Si, and Nb-Ta-Si Systems

1988 ◽  
Vol 133 ◽  
Author(s):  
K. S. Kumar ◽  
S. K. Mannan
Keyword(s):  
High Temperature ◽  
Mechanical Alloying ◽  
Mechanical Milling ◽  
Room Temperature ◽  
Crystalline Compound ◽  
X Ray Diffraction ◽  
X Ray ◽  
Β Phase ◽  
Α Phase

ABSTRACTThe mechanical alloying behavior of elemental powders in the Nb-Si, Ta-Si, and Nb-Ta-Si systems was examined via X-ray diffraction. The line compounds NbSi2 and TaSi2 form as crystalline compounds rather than amorphous products, but Nb5Si3 and Ta5Si3, although chemically analogous, respond very differently to mechanical milling. The Ta5Si3 composition goes directly from elemental powders to an amorphous product, whereas Nb5Si3 forms as a crystalline compound. The Nb5Si3 compound consists of both the tetragonal room-temperature α phase (c/a = 1.8) and the tetragonal high-temperature β phase (c/a = 0.5). Substituting increasing amounts of Ta for Nb in Nb5Si3 initially stabilizes the α-Nb5Si3 structure preferentially, and subsequently inhibits the formation of a crystalline compound.

Effects of Cooling Rate and Sn Addition on the Microstructure of Ti-Nb-Sn Alloys

2011 ◽  
Vol 172-174 ◽  
pp. 190-195 ◽  
Author(s):  
Giorgia T. Aleixo ◽  
Eder S.N. Lopes ◽  
Rodrigo Contieri ◽  
Alessandra Cremasco ◽  
Conrado Ramos Moreira Afonso ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Cooling Rate ◽  
Melting Furnace ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Β Phase ◽  
Arc Melting ◽  
Ti Alloys ◽  
Ω Phase

Ti-based alloys present unique properties and hence, are employed in several industrial segments. Among Ti alloys, β type alloys form one of the most versatile classes of materials in relation to processing, microstructure and mechanical properties. It is well known that heat treatment of Ti alloys plays an important role in determining their microstructure and mechanical behavior. The aim of this work is to analyze microstructure and phases formed during cooling of β Ti-Nb-Sn alloy through different cooling rates. Initially, samples of Ti-Nb-Sn system were prepared through arc melting furnace. After, they were subjected to continuous cooling experiments to evaluate conditions for obtaining metastable phases. Microstructure analysis, differential scanning calorimetry and X-ray diffraction were performed in order to evaluate phase transformations. Depending on the cooling rate and composition, α” martensite, ω phase and β phase were obtained. Elastic modulus has been found to decrease as the amount of Sn was increased.

Phase Constitution and Heat Treatment Behavior of Zr-Nb Alloys

2007 ◽  
Vol 561-565 ◽  
pp. 1435-1440 ◽  
Author(s):  
Masahiko Ikeda ◽  
Tsuyoshi Miyazaki ◽  
Satoshi Doi ◽  
Michiharu Ogawa
Keyword(s):  
Heat Treatment ◽  
Elastic Modulus ◽  
Elastic Moduli ◽  
X Ray Diffraction ◽  
Phase Constitution ◽  
X Ray ◽  
Β Phase ◽  
Ω Phase ◽  
Solution Treated ◽  
Α Phase

Phase constitution in the solution-treated and quenched state and the heat treatment behavior were investigated by electrical resistivity, hardness, and elastic modulus measurements, X-ray diffraction, and optical microscopy. Hexagonal martensite and the β phase were identified in the Zr-5mass%Nb alloy. β and ω phases were identified in the Zr-10 and 15mass%Nb alloys, and only the β phase was identified in the Ti-20Nb alloy. Resistivity at RT, Vickers hardness and elastic modulus increased up to 10Nb and then decreased dramatically at 15Nb. Above 15Nb, these values slightly decreased. The elastic moduli for 15Nb and 20Nb were 59.5 and 55.5 GPa, respectively. On isochronal heat treatment, the isothermal ω phase precipitated between 473 and 623 K and then the α phase precipitated in the 10Nb, 15Nb and 20Nb alloys.

The Flavonoids of Combretum quadrangulare: Crystal structures of the Polymorphic Forms of 5-Hydroxy-2-(4'-hydroxy-3',5'-dimethoxyphenyl)-3,7-dimethoxy-4H-1-benzopyran-4-one

1985 ◽  
Vol 38 (8) ◽  
pp. 1177 ◽  
Author(s):  
IR Castleden ◽  
SR Hall ◽  
S Nimgirawath ◽  
S Thadaniti ◽  
AH White
Keyword(s):  
Least Squares ◽  
Crystal Structures ◽  
X Ray Diffraction ◽  
Full Matrix ◽  
X Ray ◽  
Β Phase ◽  
Α Phase ◽  
Polymorphic Forms

The following substituted 2-phenyl-4H-1-benzopyran-4-ones have been isolated from the dried flowers of Combretum quadrangulare Kurz ( Combretaceae ): 5-hydroxy-3,3′,4′,5′,7-pentamethoxy ( combretol ) (1), 3′,5-dihydroxy-3,4′,7-trimethoxy ( ayanin ) (2) and 4′,5-dihydroxy- 3,3′,5′,7-tetramethoxy (3). The last substance (3) was obtained as a mixture of two polymorphic forms (α and β) each of which was characterized by X-ray diffraction. Diffractometer data at 295 K were refined by full matrix least squares to residuals of 0.043 (1181 'observed' reflections) for the α-phase and 0.044 (1421) for the β phase of (3). Crystals of the α-phase of (3) are triclinic, Pī, a 12.663(6), b 9.592(4), c 7.444(4) Ǻ, α 102.48(3), β 101.39(4), γ 91.72(4)°,Z 2. Crystals of the β-phase of (3) are monoclinic P21/n, a 17.139(8), b 12.728(6), c 7.845(7) Ǻ, β 95.07(6)°, Z 4. An unambiguous synthesis of (3) was also achieved.

Brillouin scattering near the α–β phase transitions of N2 and CO

1988 ◽  
Vol 66 (4) ◽  
pp. 541-548 ◽  
Author(s):  
V. Askarpour ◽  
H. Klefte ◽  
M. J. Clouter
Keyword(s):  
Phase Transition ◽  
Single Crystals ◽  
Elastic Constants ◽  
Brillouin Scattering ◽  
X Ray Diffraction ◽  
X Ray ◽  
Β Phase ◽  
Α Phase ◽  
Mode Softening ◽  
Cubic Structure

The technique of high resolution Brillouin spectroscopy has been used to determine the adiabatic elastic constants of single crystals of β-N2 and β-CO as a function of temperature, in an effort to study the α–β phase transition. For all elastic constants, there is an increase of approximately 1%/K on cooling and there is no evidence of further mode softening, even within 0.5 K of the phase transition. Three large single crystals of α-CO were grown. The orientations were determined, by Laue X-ray diffraction, and correlated to the orientations of the parent β-crystals. The β-phase hexagonal basal planes appear to transform to planes of the form {110} in the α-phase cubic structure.

Thermal and X-Ray Diffraction Studies of Doped and Undoped Single Crystal and Polycrystalline BaTiO3

1994 ◽  
Vol 360 ◽  
Author(s):  
L.G. Carreiro ◽  
J.V. Marzik ◽  
K.K Deb
Keyword(s):  
Solid Solution ◽  
Curie Temperature ◽  
Single Crystal ◽  
Dopant Concentration ◽  
Infrared Detection ◽  
Thermal Transition ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Mole Percent ◽  
X Ray

AbstractCalorimetric changes in a series of pure and doped single crystal and polycrystalline BaTiO3 were studied using differential scanning calorimetry over the temperature range of-110°C to 200°BC. The dopants, oxides of niobium and iron were varied from 0.5 to 8 mole percent, and strontium was varied from 5 to 35 mole percent. Endotherms were observed corresponding to three crystallographic transitions. The highest observed thermal transition corresponds to a tetragonal to cubic crystallographic transition and is also associated with the Curie temperature in these materals. Two additional endothermic transitions were also observed, an intermediatetemperature orthorhombic to tetragonal transition, and a low-temperature rhombohedral to orthorhombic transition. The three dopants decreased the crystallographic transition temperatures and Curie temperature as the dopant concentration was increased. X-ray diffraction was used to identify phases present and to determine the extent of solid solution. It is expected that these materials will display improved infrared detection as well as opto-electronic properties.

scholarly journals Polar and non-polar structures of NH4TiOF3

2019 ◽  
Vol 52 (1) ◽  
pp. 23-26
Author(s):  
O. Boytsova ◽  
I. Dovgaliuk ◽  
D. Chernyshov ◽  
A. Eliseev ◽  
P. O'Brien ◽  
...  
Keyword(s):  
Room Temperature ◽  
Phase 1 ◽  
Structural Features ◽  
X Ray Diffraction ◽  
X Ray ◽  
Β Phase ◽  
Α Phase ◽  
Starting Compound ◽  
Different Temperatures ◽  
Fourfold Axis

Ammonium oxofluorotitanate, NH4TiOF3, is probably the best known precursor for the synthesis of anatase mesocrystals. Transformation of NH4TiOF3 into TiO2 through thermal decomposition, accompanied by hydrolysis, preserves some structural features of the precursor. Currently, any discussion of the mechanism of this transformation is difficult, as the exact crystal structure of the starting compound is not available and no intermediate structures are known. This article describes the outcome of single-crystal and powder X-ray diffraction studies, revealing the existence of two polymorphs of the parent NH4TiOF3 at different temperatures. A second-order phase transition from the polar Pca21 α phase (1), stable at room temperature, to the Pma2 β phase (2) above ∼433 K has been demonstrated. The direction of the pseudo-fourfold axis in NH4TiOF3 coincides with the orientation of the fourfold axis of anatase mesocrystals, consistent with a topotactical transformation.

scholarly journals Phase Transition and Melt-Recrystallization Behavior of Poly(Butylene Adipate) Investigated by Simultaneous Measurements of Wide-Angle X-Ray Diffraction (WAXD) and Differential Scanning Calorimetry (DSC)

Polymers ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 75
Author(s):  
Mengfan Wang ◽  
Weiyu Cao
Keyword(s):  
Phase Transition ◽  
Differential Scanning Calorimetry ◽  
Heating Process ◽  
Wide Angle ◽  
Melt Crystallization ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Β Phase ◽  
Simultaneous Measurements

Simultaneous measurements of wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) were carried out to investigate the phase transition and melting behaviors of poly(butylene adipate) (PBA). Thermal expansion changes along the a and b axes of the β form unit cell are different from each other during the heating process. At the beginning of the β to αH (high-temperature α phase) phase transition, the β phase melts very fast, while the recrystallization of the αH phase is delayed and slowed. With the further increment of the temperature, the melting rate of the β phase slows down, while the recrystallization of the αH phase accelerates. The diffraction peak intensity ratios of the β(020):β(110) and αH(020):αH(110) diffraction peaks during the first heating process have similar value. However, the above value is different from the value of α(020):α(110) during the following melt-crystallization process. This difference comes from the different orientations of the crystal lattices of the α and αH(β) crystals to the substrate plane, which indicates that the αH phase inherits the orientation of the β phase during phase transition and the orientation of αH form crystals is different from the α form crystals that crystallized from the melt.

Structural Properties of β-FeSi2 Bulk Crystal Grown by Horizontal Gradient Freeze Method

1995 ◽  
Vol 402 ◽  
Author(s):  
H. Kakemoto ◽  
Y. Tsaic ◽  
A. C. Beye ◽  
H. Katsumata ◽  
S. Sakuragi ◽  
...  
Keyword(s):  
High Purity ◽  
Equilibrium Phase ◽  
Equilibrium Phase Diagram ◽  
Growth Conditions ◽  
Horizontal Gradient ◽  
X Ray Diffraction ◽  
X Ray ◽  
Β Phase ◽  
Α Phase ◽  
Micro Analysis

AbstractWe report on the synthesis of β-FeSi2 bulk materials using Horizontal Gradient Freeze (HGF) method. Chunk and powder FeSi2 or high-purity Fe (4N) and Si (9N) were used as starting materials. Three values (1:2, 2:5 and 1:3) of the Fe:Si ratio were selected in the very narrow α and β ranges of the equilibrium phase diagram. Samples were melted between 1300°C and 1500°C in high purity graphite crucibles covered with boron nitride. After cooling, the samples were kept at 800°C and 900°C during 66 to 100 hours, leading to transformation from α to β phase. Cooling rate and annealing time were taken as the two main parameters to optimize the growth conditions. Principal structural characterization was made by X-ray diffraction (XRD). Correlation with stoichiometry was achieved using the results of Rutherford Backscattering Spectroscopy (RBS) and Electron Probe X-Ray Micro Analysis (EPXMA). The samples obtained from 1:2 ratio exhibited mainly β phase while the 2:5 ratio specimens revealed almost α phase structure. The samples prepared with 1:3 ratio was found as a mixture of α and β phases under Si-rich conditions.

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