MICROSTRUCTURAL EVOLUTION OF Al-Cu-Mg-Ag ALLOY WITH TRACE Zr ADDITION DURING TWO-STEP HOMOGENIZATION

2009 ◽  
Vol 23 (06n07) ◽  
pp. 855-862 ◽  
Author(s):  
FEIYUE MA ◽  
ZHIYI LIU
Keyword(s):  
Melting Point ◽  
Grain Boundaries ◽  
Microstructural Evolution ◽  
Cast Alloy ◽  
Scanning Calorimetry ◽  
Zr Addition ◽  
Homogenization Time ◽  
The Matrix ◽  
Higher Temperature ◽  
Lower Temperature

The microstructural evolution in an Al - Cu - Mg - Ag alloy with trace Zr addition during homogenization treatment was characterized by Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray Spectroscopy (EDS). It was shown that the low-melting-point phase segregating toward grain boundaries is Al 2 Cu , with a melting point of 523.52°C. A two-step homogenization process was employed to optimize the microstructure of the as-cast alloy, during which the alloy was first homogenized at a lower temperature, then at a higher temperature. After homogenized at 420°C for 6 h, Al 3 Zr particles were finely formed in the matrix. After that, when the alloy was homogenized at an elevated temperature for a longer time, i.e., 515°C for 24 h, most of the precipates at the grain boundaries were removed. Furthermore, the dispersive Al 3 Zr precipitates were retained, without coarsening greatly in the final homogenization step. A kinetics model is employed to predict the optimal homogenization time at a given temperature theoretically, and it confirms the result in present study, which is 420°C/6h+515°C/24h.

STRUCTURAL, ELECTRICAL AND MAGNETIC PROPERTIES OF Pr1-xBaxMnO3(x=0.33–0.80)

2007 ◽  
Vol 21 (15) ◽  
pp. 2647-2656 ◽  
Author(s):  
NEERAJ PANWAR ◽  
S. K. AGARWAL ◽  
G. L. BHALLA ◽  
D. KAUR ◽  
D. K. PANDYA
Keyword(s):  
Grain Boundaries ◽  
Structural Parameters ◽  
Size Difference ◽  
Strain Effect ◽  
Temperature Transition ◽  
Low Field ◽  
Ionic Size ◽  
Higher Temperature ◽  
Lower Temperature ◽  
Magneto Resistance

We report here the electrical resistivity, ac susceptibility, low field magneto-resistance (LFMR) and structural parameters of the Pr 1-x Ba x MnO 3(x= 0.33–0.80) system. Samples with 33% and 40% Ba -content exhibit two clear transitions in their resistivity-temperature behavior while signatures of higher temperature transition are also seen in the 50% Ba sample. The higher temperature transition (insulator-metal, Tp1), like in other CMR materials, results due to competition between the double exchange and super exchange mechanisms. The lower temperature broad hump (Tp2) in resistivity reflects the strain effect at the grain boundaries due to the ionic radii mismatch between Pr +3 and Ba +2. The low field magneto-resistance (at 0.15T) also corroborates the above results as MR peaks near Tp1 and increases further at lower temperatures, reflecting the contribution from the grain boundaries. Susceptibility measurements show the Curie transition (Tc) to be near Tp1 of the ρ-T data. Results are found to be consistent with the (NdBa) MnO 3 and (LaBa) MnO 3 systems. Resistivity data on the Pr 0.67 Sr 0.33 MnO 3 system, where the lower temperature transition at Tp2 is not seen due to the smaller ionic size difference of ( Pr +3– Sr +2) compared to ( Pr +3– Ba +2), also substantiate these results. The observed resistivity upturn at low temperatures is considered in terms of the ensuing localization of carriers due to the varying degree of ionic size mismatch in these systems.

Preparation and Characterization of Multiwalled Carbon Nanotubes-Reinforced pCBT by Ring-Opening Polymerization of Cyclic Butylene Terephthalate

2016 ◽  
Vol 848 ◽  
pp. 125-131
Author(s):  
Yin He Su ◽  
Jun Rong Yu
Keyword(s):  
Carbon Nanotubes ◽  
Multiwalled Carbon Nanotubes ◽  
Ring Opening ◽  
Ring Opening Polymerization ◽  
Scanning Calorimetry ◽  
Multiwalled Carbon ◽  
Butylene Terephthalate ◽  
Cyclic Butylene Terephthalate ◽  
The Matrix ◽  
Higher Temperature

Multiwalled carbon nanotubes (MWCNT)-reinforced polymerized cyclic butylene terephthalate (pCBT) nanocomposites were prepared by in situ ring opening polymerization of cyclic butylene terephthalate oligomers (CBT). The results of differential scanning calorimetry (DSC) indicated that the melting peak located at the low temperature (Tm1) increased and that at higher temperature (Tm2) decreased with the increasing of content of the MWCNT. During the cooling the MWCNT served as nucleation points from where crystallization can start. The more the MWCNT in the system the earlier the crystallization starts. The Morphological investigations performed by scanning electron microscopy (SEM) shown that the MWCNT were embedded in the matrix and held tightly by the matrix. The modulus and strength increased with MWCNT concentration in the nanocomposites, however, the elongation at break, absorbed energy at break and impact strength were decreased with the increasing of MWCNT content.

scholarly journals Effect of Aromatic Petroleum Resin on Damping Properties of Polybutyl Methacrylate

Polymers ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 543
Author(s):  
Songhan Wan ◽  
Saisai Zhou ◽  
Xing Huang ◽  
Songbo Chen ◽  
Shuwei Cai ◽  
...  
Keyword(s):  
Mechanical Analysis ◽  
Damping Properties ◽  
Scanning Calorimetry ◽  
Sem Images ◽  
Dynamical Mechanical Analysis ◽  
Petroleum Resin ◽  
The Matrix ◽  
Higher Temperature ◽  
Dsc Curves ◽  
Positive Effect

The damping properties of polybutyl methacrylate (PBMA)/aromatic petroleum resin (C9) composite were investigated in this work. In particular, a trace of styrene (St) was introduced to copolymerize with PBMA to improve the compatibility between C9 and matrix. The structure of the copolymer, P(BMA-co-St), was characterized by FTIR and 1HNMR. The P(BMA-co-St)/C9 composites were tested by differencial scanning calorimetry (DSC), scanning electron microscopy (SEM) and dynamical mechanical analysis (DMA). DSC curves of all P(BMA-co-1wt%St)/C9 composites expressed only one glass transition temperature (Tg). SEM images showed that C9 had good compatibility with the matrix after St was introduced. DMA curves indicated that the addition of C9 had a positive effect on the damping properties of PBMA. The loss tangent (tanδ) peak moved to a higher temperature with the increment content of C9, and the effective damping temperature range increased significantly. The influence of aromatic resin C9 and aliphatic resin (C5) on PBMA damping performance was compared. It was further shown that C9 with benzene ring effectively improved the damping performance of PBMA.

Isostructural phase transition in m-carboxyphenylammonium monohydrogenphosphite

2005 ◽  
Vol 61 (6) ◽  
pp. 700-709 ◽  
Author(s):  
El-Eulmi Bendeif ◽  
Slimane Dahaoui ◽  
Michel François ◽  
Nourredine Benali-Cherif ◽  
Claude Lecomte
Keyword(s):  
Phase Transition ◽  
Reciprocal Lattice ◽  
Forthcoming Paper ◽  
Unit Cell ◽  
Temperature Phase ◽  
Data Sets ◽  
Scanning Calorimetry ◽  
Cell Parameters ◽  
Higher Temperature ◽  
Lower Temperature

Crystals of m-carboxyphenylammonium monohydrogenphosphite, C7H8NO_{2}^+·H2PO_3^{-} (m-CPAMP), space group P2_{1}/c, grown from aqueous solution undergo a reversible first-order single-crystal phase transition at Tc = 246 (2) K with a hysteresis of 3.6 K. The thermal behaviour of the sample was characterized by differential scanning calorimetry (DSC) experiments. Variations of the unit-cell parameters versus temperature between 100 and 320 K are reported. The transition from the higher-temperature phase (HTP) to the lower-temperature phase (LTP) is characterized by a unit-cell volume contraction of 1.77%. The average structure and unit-cell packing of m-CPAMP at lower temperature (100 K) are reported from accurate X-ray data sets and compared with those of the higher-temperature phase (293 K) in order to investigate the mechanism of the phase transition. The reciprocal lattice reconstruction showed a few very weak satellite reflections which will be discussed in a forthcoming paper.

scholarly journals Base–compositional biases and the bat problem. I. DNA–hybridization melting curves based on AT– and GC–enriched tracers

1998 ◽  
Vol 353 (1367) ◽  
pp. 369-379 ◽  
Author(s):  
John D. Pettigrew ◽  
John A. W. Kirsch
Keyword(s):  
Melting Point ◽  
Dna Hybridization ◽  
Gc Content ◽  
The Self ◽  
Anomalous Behaviour ◽  
Melting Points ◽  
Fractionation Method ◽  
Measured Distance ◽  
Higher Temperature ◽  
Lower Temperature

We explored the interordinal relationships of mammals using DNA–DNA hybridization, with particular reference to the much–debated problem of whether the megabats and microbats are more closely related to each other than the megabats are to primates. To try to improve resolution when taxa are distantly related and the melting points of hybrids are low and difficult to distinguish, we increased the GC–content of DNA by a fractionation method that used the same melting–point apparatus also used in the hybridization studies. When we used GC–rich DNA as the tracer to make hybrids, the melting point of the self–hybrid shifted to a higher temperature as expected, but the behaviour of heterologous hybrids varied with the taxa being compared. When the melting point of the heterologous hybrid also shifted to a higher temperature so that the two compared taxa maintained the same or proportional distance, we called this ‘following behaviour’, because the heterologous hybrid made with GC– tracer ‘followed’ the GC– self– to higher temperatures. We also commonly saw anomalous behaviour, where the melting point of the heterologous hybrid shifted to a lower temperature when compared with an AT– hybrid. In these anomalous cases, the distance measured between the taxa increased markedly as a result of GC–, indicating that an underestimate of distance may have resulted from AT– in DNA. This inference was supported by the finding that it was rare to observe a decrease in measured distance between taxa using GC– DNA, but very common to find an increase as would be expected from the generally higher AT–contents of eutherian DNAs. Moreover, the most extreme cases, where distances changed most using GC–rich DNA, were usually those involving comparisons between taxa known to have the most extreme AT–biases among mammals, such as the megabats and rhinolophoid (including megadermatid) microbats. Our results show that AT–bias in eutherian DNA leads to consistent underestimates of measured differences between taxa with extreme AT–biases.

Characterisation of Al-Cu and Al-Mg-Si Free-Cutting Alloys

2014 ◽  
Vol 794-796 ◽  
pp. 1181-1186 ◽  
Author(s):  
Miroslav Karlík ◽  
Jiri Faltus ◽  
Jitka Nejezchlebová ◽  
Petr Haušild ◽  
Petr Harcuba
Keyword(s):  
Melting Point ◽  
Impact Testing ◽  
Solution Annealing ◽  
Scanning Calorimetry ◽  
Slow Cooling ◽  
X Ray ◽  
Temperature Solution ◽  
Higher Temperature ◽  
The Impact ◽  
Scanning Electron

Free cutting alloys of Al-Cu (AA2011 and AA2111B) in T6 temper and Al-Mg-Si system (AA6023 and AA6262) in tempers T6 and T8 were subjected to Charpy U - notch impact testing at the temperatures ranging from 20°C to 350°C. The microstructure of the materials was characterized by light metallography, fracture surfaces were observed using scanning electron microscope (SEM). The alloys showed a significant decrease in the impact energy KU at temperatures ~125°C (AA2011, AA2111B), ~170°C (AA6023), and ~250°C (AA6262), respectively. This decrease of KU was caused by melting of disperse phases containing low-melting point metals (Pb, Sn, Bi), which was confirmed by differential scanning calorimetry. Additional annealing of the AA6262-T8 alloy for 2h at 400°C followed by slow cooling led to the transformation of Pb + Bi particles accompanied by the shift of the melting temperature from ~250 to ~310 °C. Higher temperature solution annealing of the AA6023 alloy for 30 min at 540°C (as a replacement of common 30 min at 520°C) resulted in a partial transformation of Sn + Bi particles accompanied by melting point shift from ~170 to ~200°C. Chemical composition of the corresponding phases was monitored by energy dispersive X-ray spectroscopy in SEM.

Crossover of the Curing Mechanisms and Double Glass Transition Temperatures of Tetrabromo-Bisphenol-a Epoxy Resin with 4,4-Diaminodiphenylsulfone

2011 ◽  
Vol 233-235 ◽  
pp. 2029-2033 ◽  
Author(s):  
Xing Fang Yao ◽  
Shi Feng Zhang
Keyword(s):  
Glass Transition ◽  
Bisphenol A ◽  
Epoxy Resin ◽  
Transition Temperatures ◽  
Scanning Calorimetry ◽  
Glass Transition Temperatures ◽  
Autocatalytic Model ◽  
Maximum Reaction ◽  
Higher Temperature ◽  
Lower Temperature

The curing process of tetrabromo-bisphenol-A epoxy resin (TBBPAER) with 4,4´-diaminodiphenylsulfone (DDS) was investigated by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and torsional braid analysis (TBA) methods. FTIR results indicated that the maximum reaction velocity was observed at initial stages at higher temperature, but it was occurred at conversion =10 - 40 % at lower temperature. It showed that there is the crossover from the autocatalytic model to the nth-order mechanism when the temperature was increased. While the double glass transition temperatures occuring in the system, according to the microstructure of the reactant, a theoretical and reasonable explanation may arise from this article.

Influence of Deformation on Precipitation Kinetics in Mg-Tb Alloy

2012 ◽  
Vol 322 ◽  
pp. 151-162 ◽  
Author(s):  
Oksana Melikhova ◽  
Jakub Čížek ◽  
Petr Hruška ◽  
Marián Vlček ◽  
Ivan Procházka ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
Grain Boundaries ◽  
Positron Annihilation ◽  
High Pressure Torsion ◽  
Coarse Grained ◽  
Scanning Calorimetry ◽  
Fine Grained ◽  
Β Phase ◽  
Lower Temperature

Precipitation effects in age-hardenable Mg-13wt.%Tb alloy were investigated in this work. The solution treated alloy was subjected to isochronal annealing and decomposition of the supersaturated solid solution was investigated by positron annihilation spectroscopy combined with transmission electron microscopy, electrical resistometry, differential scanning calorimetry and microhardness measurements. Peak hardening was observed at 200°C due to precipitation of finely dispersed particles of β phase with the D019structure. Vacancy-like defects associated with β phase particles were detected by positron annihilation. At higher temperatures precipitation of β and subsequently β phase takes place. Formation of these phases lead to some additional hardening and introduces open volume defects at precipitate/matrix interfaces. To elucidate the effect of plastic deformation on the precipitation sequence we studied also a Mg-13wt.%Tb alloy with ultra fine grained structure prepared by high pressure torsion. In the ultra fine grained alloy precipitation of the β phase occurs at lower temperature compared to the coarse grained material and the peak hardening is shifted to a lower temperature as well. This effect can be explained by enhanced diffusivity of Mg and Tb atoms due to a dense network of grain boundaries and high density of dislocations introduced by severe plastic deformation. Moreover, dislocations and grain boundaries serve also as nucleation sites for precipitates. Hence, precipitation effects are accelerated in the alloy subjected to severe plastic deformation.

scholarly journals Investigation of melting and crystallization processes of fat components of praline masses

2018 ◽  
Vol 80 (2) ◽  
pp. 323-327
Author(s):  
I. A. Saranov ◽  
I. A. Kuznetsov ◽  
I. V. Kuznetsova ◽  
G. O. Magomedov
Keyword(s):  
Solid State ◽  
Coconut Oil ◽  
Endothermic Reaction ◽  
Optimal Parameters ◽  
Scanning Calorimetry ◽  
Temperature Range ◽  
The Matrix ◽  
Lower Temperature ◽  
Melting And Crystallization Temperatures ◽  
Melting And Crystallization

The processes of melting and crystallization of lauric fat KS35 and coconut oil by the method of differential scanning calorimetry were studied. The process of crystallization of coconut oil takes place in the temperature range 13.1–15.9 °C, while heat is released 118.3 J/g. The process of crystallization of lauric fat KS35 occurs in the temperature range 20.4–25.9 °C, with a heat release of 152.7 J / g. Lauric fat melts in the range of 28.7–33.9 °C, 147.4 J/g is absorbed during this endothermic reaction. Temperature interval, the heat effect of melting coconut oil is lower (18.3–26.4 °C, 95.5 J / g). Reduction of melting and crystallization temperatures of coconut oil in comparison with lauric fat proves that the composition of coconut oil includes a greater number of unsaturated acids, the crystallization and melting of which occurs at a lower temperature than saturated ones.In the paper, the possibility is of using DSC data for determining optimal parameters for forming and cutting praline masses in the production of praline candies. Forming should be done after holding the praline mass in the temperature range 20-26 °C, with most of the triglycerides of lauric fat having a solid state, which allows the molded praline tow to keep its shape and not spread after exiting the matrix. It is advisable to cut praline tows on candies at a temperature of 13 – 16 °C, since in this range most of the triglycerides and coconut oil have a solid state, which makes it possible not to crush the tourniquet and sweets during cutting..

scholarly journals The Effects of Solutionizing and Aging temperature on the Microstructure of Allvac 718plus

2019 ◽  
Author(s):  
Geeta Kumari ◽  
Carl Boehlert ◽  
S. Sankaran ◽  
M. Sundararaman
Keyword(s):  
Grain Boundaries ◽  
Microstructural Evolution ◽  
Aging Temperature ◽  
Volume Fraction ◽  
Aging Treatment ◽  
High Volume ◽  
The Other ◽  
Gamma Prime ◽  
The Matrix ◽  
Δ Phase

Abstract A study on the microstructural evolution of a Ni-based superalloy, Allvac 718Plus, in the forged condition, was performed by varying the solutionizing temperature. Different solutionizing temperatures were chosen to obtain different fractions of the gamma prime (Ni3(Al,Ti,Nb), γ’) and delta (Ni3Nb, δ) phase precipitates. The solutionizing temperatures ranged between 945°C to 1100°C. After solutionizing, the samples were subjected to a standard two-step aging treatment (788°C for 8h followed by 704°C for 8h). The 954°C solutionizing treatment resulted in incomplete dissolution of the γ’ phase and a relatively high volume fraction of the δ phase, which formed preferentially at grain boundaries. The γ’ phase was completely dissolved during each of the other three solutionizing treatments (1000°C, 1050°C, and 1100°C), while the fraction of the δ phase decreased with increasing solutionizing temperature. The 1100°C solutionizing treatment led to significant growth of the matrix grains (Ni (FCC), γ).

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