A phase transformation study in the BaO · Al2O3 · 2SiO2 (BAS)–Si3N4 system

1995 ◽  
Vol 10 (12) ◽  
pp. 3143-3148 ◽  
Author(s):  
A. Bandyopadhyay ◽  
P.B. Aswath
Keyword(s):  
Phase Transformation ◽  
Phase Transformations ◽  
Metastable Phase ◽  
Heat Treating ◽  
Intermediate Step ◽  
Hexagonal Form ◽  
Heat Treated ◽  
Different Temperatures ◽  
Barium Aluminosilicate ◽  
Transformation Study

A phase transformation study was carried out with barium aluminosilicate (BAS) forming powders (BaCO3, Al2O3, and SiO2) in a BAS-Si3N4 system. Powders were heat-treated in air at 1 atm pressure at different temperatures from 600 to 1150 °C at an interval of 50 °C to study the phase transformations during the formation of BAS. The phase transformations of α to β-Si3N4 is studied by heat-treating the powders at 1600 °C for different sintering times in a nitrogen environment at 1 atm pressure. Formation of different phases was identified by using powder x-ray diffraction. Formation of different forms of barium silicates occurs as an intermediate step between 650 and 950 °C and hexagonal BAS forms between 900 and 950 °C. The hexagonal form of BAS always forms first and persists as a metastable phase in the composites with no evidence of the monoclinic phase. An attempt made to fully transform hexagonal BAS to monoclinic BAS by using LiF as a mineralizer proved to be successful. The hexagonal form of BAS forms first when heat-treated at 1000 °C and is fully transformed to monoclinic BAS when heat-treated at 1100 °C.

Microstructure and Phase Transformation of Super-High Pressure Mg-Li Alloy

2015 ◽  
Vol 816 ◽  
pp. 375-380 ◽  
Author(s):  
Qiu Ming Peng ◽  
Hui Fu ◽  
Yan An Wang ◽  
Hui Li
Keyword(s):  
High Pressure ◽  
Phase Transformation ◽  
Heat Treating ◽  
Dendritic Morphology ◽  
Metallic Materials ◽  
Cast Sample ◽  
Temperature Range ◽  
Electronic Distribution ◽  
Heat Treated ◽  
Dislocation Movement

Super-high pressure (SHP) changes crystal structure and electronic distribution of metallic materials, which plays an important role in properties. Herein, a duplex Mg-7%wt.Li alloy was heat-treated under SHP (2 GPa) by cubic-anvil large-volume press with six rams for 2 h in the temperature range of 450~1350 °C. Microstructure, phase transformation behavior and mechanical properties were examined. Compared with the as-cast sample, the SHP samples after heat-treating from 450 °C to 750 °C under 2 GPa were composed of twinning in addition to duplex structure. Comparatively, the samples treated between 1050 °C and 1350 °C exhibit typical dendritic morphology. Phase transformation from Li3Mg7 phase or Li0.92Mg4.08 phase to Li3Mg17 phase occurred during the whole investigated temperature range, in which only the Li3Mg17 phase maintained when the temperature exceeds 1050 °C. The microhardness of the sample prepared at 750 °C under 2 GPa was 73.15HV, which is 1.5 times higher than that of the as-cast one. The improved microhardness is mainly attributed to the formation of nanosized twins during SHP treatment. These fine twins effectively prohibit the dislocation movement during deformation. It reveals the SHP is an effective approach to prepare high performation Mg alloys.

Metastable Phase Transformations in Ti-40Al-10V Alloy

1994 ◽  
Vol 364 ◽  
Author(s):  
G. Shao ◽  
P. Tsakiropoulos ◽  
A. P. Miodownik
Keyword(s):  
Phase Transformation ◽  
Phase Transformations ◽  
Volume Fraction ◽  
Metastable Phase ◽  
Equilibrium Phase ◽  
Rapid Quenching ◽  
Β Phase ◽  
Transformation Sequence ◽  
Melt Spun ◽  
Melt Spun Ribbons

AbstractThe microstructures in arc melted ingots and melt spun ribbons have been investigated by electron microscopy and thermodynamic modelling has been used to study the phase transformations. In the ingot, solidification starts with the bcc β phase and at room temperature the structure consists of B2, ωordered, γ and α2 phases. The calculated equilibrium phase transformation sequence during cooling is L → L+ β→β→β + α→β2+α → α+β2+γ → α2+γ + B2. The phase transformation sequence is dramatically changed by rapid quenching from the melt. Athermal ordered w phase is formed in metastable B2 and the α→α2 ordering process is completely suppressed in the melt spun ribbons. The volume fraction of the α precipitates is also dependent on cooling rates.

Peritectoid carbide transformation based on ε-carbide Fe2C in Fe-C-system alloys. Part 1. Basics of theory

2020 ◽  
pp. 15-21
Author(s):  
S. V. Davydov ◽  
Keyword(s):  
Phase Transformation ◽  
Phase Transformations ◽  
Metastable Phase ◽  
State Diagram ◽  
Stable Phase ◽  
Cement Slurry ◽  
Two Phase ◽  
Peritectoid Transformation ◽  
Decomposition Phase ◽  
Carbon System

In the present work low-temperature carbide phase transformations in the system of Fe-C alloys based on ε-сarbide Fe2C with consideration of identification of θ-Fe3C cement as a solid solution were studied. It has been proved that the θ-Fe3C cement slurry is colourfastonide, and the ε-Fe2C carbide slurry is bertollide. When tempering hardened steels, ε-сarbide Fe2C is emitted in the structure of hardened martensite, which is absent in the phase diagram of iron-carbon system alloys. It is believed that ε-сarbide Fe2C is not a stable phase, and since it is metastable, it is formed only in quenched steels under non-equilibrium conditions. The isolation and dissolution of ε-сarbide Fe2C is a classic phase transformation and the absence of this transformation on the diagram is not caused by the metastable phase of ε-сarbide Fe2C, but by the incomplete iron-carbon diagram. The martensite decomposition phase transformation is based on the formation of carbon enriched zones. The processes of carbon segregation on dislocation structures and grid planes of martensite create zones with excess energy. Beginning approximately with temperature 100 °С in structure of martensite begins to allocate ε-сarbide Fe2C, finishing a stage of two-phase segregational disintegration of martensite. At rather small concentrations of carbon in cluster zones the fastest and most effective way of relaxation of redundant energy in these zones, as well as in the tetragonal lattice of martensite is the formation of phases with low value of work of nucleation, first of all ε-сarbide Fe2C and α-Fe(C) or ferrite. The main stages of phase transformations in the peritectoid reaction of martensite decomposition are considered. It is proposed to introduce the peritectoid transformation horizontal at 382 °C and the peritectic transformation horizontal of cement at 1650 °C into the Fe-C alloy state diagram.

Effects of Different Heat Treatment Temperatures on the Properties of Quartz Fibers

2010 ◽  
Vol 105-106 ◽  
pp. 115-118 ◽  
Author(s):  
Qi Hong Wei ◽  
Chong Hai Wang ◽  
Zhi Qiang Cheng ◽  
Ling Li ◽  
Hong Sheng Wang ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Tensile Strength ◽  
Phase Transformation ◽  
Fiber Strength ◽  
Single Fiber ◽  
Significant Phase ◽  
Surface Micromorphology ◽  
Heat Treated ◽  
Different Temperatures ◽  
Crystallization Heat

In this paper, XRD was engaged in studying phase transformation of quartz fibers, SEM was engaged in studying the surface micromorphology of quartz fibers heat treated at different temperatures, and the tensile strength was measured by a single fiber strength electronics instrument. The results indicate that surface infiltration agent have been iliminated after heat treatment at 500°C, and the tensile strength decreaced significantly. The higher the temperature was, the more the tensile strength decreaced. There were no significant phase transformation and no crystallization heat treatmented at 500~800°C. But there were some round and strip bulges, and scap defects on the surface. With temperature increasing,some scab defects and bulges began to flake off, and some new rifts and cracks were formed. This was one of the important factors that decreaced tensile strength markedly.

Effect of Heat Treating Temperature on Chemical and Physical Properties of Natural Hydroxyapatite Produced From Bovine Bone

2009 ◽  
Author(s):  
Mousa Younesi ◽  
Mehdi Javidi ◽  
Mohammad Ebrahim Bahrololoom ◽  
Hamidreza Fooladfar
Keyword(s):  
Physical Properties ◽  
Diffraction Analysis ◽  
Heat Treating ◽  
White Powder ◽  
Bovine Bone ◽  
X Ray Diffraction ◽  
X Ray ◽  
Heat Treated ◽  
Different Temperatures ◽  
Natural Hydroxyapatite

This study focused on chemical and physical properties of Hydroxyapatite powder was prepared by burning bone and heat treating the obtained bone ash at different temperatures (600, 700, 800, and 1100 °C) in an air furnace. The black ash was converted to a white powder after heat treatment. Results of X-ray diffraction analysis and Fourier transform infra-red spectroscopy that were done on heat treated powders in different temperatures indicated that the white powder was hydroxyapatite and did not contain any organic components of the bone. Furthermore, results of X-ray diffraction analysis were shown that phase transformation of the resulted hydroxyapatite to other calcium phosphate phases did not occur up to 1100 °C. X-ray fluorescence analyses revealed that calcium and phosphorous were the main elements and magnesium and sodium were present as minor impurities. The results of the energy dispersive X-ray analysis showed that Ca/P ratio of this natural hydroxyapatite varies between 1.46 and 2.01. The resulted material was found to be thermally stable up to 1100 °C. The density of natural hydroxyapatite heat treated at 800 °C was measured to be 3.187 g/cm3.

scholarly journals Effect of heat treatment on microstructure, microhardness and corrosion resistance of ZE41 Mg alloy

2019 ◽  
Vol 63 (2) ◽  
pp. 79-85 ◽  
Author(s):  
Prasad U. Syam ◽  
V. V. Kondaiah ◽  
K. Akhil ◽  
V. Vijay Kumar ◽  
B. Nagamani ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Corrosion Resistance ◽  
Intermetallic Phase ◽  
Secondary Phase ◽  
Heat Treating ◽  
Treatment Temperature ◽  
Mg Alloy ◽  
Aerospace Applications ◽  
Heat Treated ◽  
Different Temperatures

Abstract Magnesium and its alloys are now attracting a great attention as promising materials for several light weight engineering applications. ZE41 is a new Mg alloy contains Zinc, Zirconium and Rare Earth elements as the important alloying elements and is widely used in aerospace applications. In the present study, heat treatment has been carried out at two different temperatures (300 and 335 °C) to assess the effect of heat treatment on microstructure and corrosion behavior of ZE41 Mg alloy. The grain size was observed as almost similar for the unprocessed and heat treated samples. Decreased amount of secondary phase (MgZn2) was observed after heat treating at 300 °C and increased intermetallic phase (Mg7Zn3) and higher number of twins appeared for the samples heat treated at 335 °C. Microhardness measurements showed increased hardness after heat treating at 300 °C and decreased hardness after heat treating at 335 °C which can be attributed to the presence of higher supersaturated grains after heat treating at 300 °C. The samples heat treated at 335 °C exhibited better corrosion resistance compared to those of base materials and samples heat treated at 300 °C. From the results, it can be understood that the selection of heat treatment temperature is crucial that depends on the requirement i.e. to improve the microhardness or at the loss of microhardness to improve the corrosion resistance of ZE41 Mg alloy.

Liquid-Liquid Phase Separation and Phase Diagrams of Simulated Fernald Waste Glasses

1993 ◽  
Vol 333 ◽  
Author(s):  
E. Wang ◽  
F. Perez-Cardenas ◽  
H. Kuang ◽  
A.C. Buechele
Keyword(s):  
Electron Microscope ◽  
Phase Separation ◽  
Heat Treating ◽  
Liquidus Curve ◽  
Miscibility Gap ◽  
Transmission Electron ◽  
Heat Treated ◽  
The Matrix ◽  
Different Temperatures ◽  
Liquid Liquid Phase Separation

ABSTRACTPrevious study of crystallization behavior in heat-treated Fernald waste glasses has produced an extensive data base of crystal phases likely to appear in various composition ranges and their corresponding liquidus temperatures. In addition, we have frequently observed amorphous phase separation in these glasses and, occasionally, evidence of crystallization originating from such phase separation. These glasses contain more than 10 components. The composition ranges for the major components are: MgF2 10–26 wt%; CaO 4–27 wt%; Al2O3 3–15 wt%; SiO2 25–40 wt%. The morphology of the phase separation as observed in the Scanning Electron Microscope (SEM) is dark, spherical globules dispersed in a continuous matrix. Globules are depleted in Mg, Ca and F, and enriched in Al and Si compared to the matrix. Phase separation occurs more frequently in melts relatively higher in Si and F. A more systematic study on a simplified and simulated seven component system (Al2O3, B2O3, CaO, Fe2O3, SiO2, Na2O and MgF2) has been undertaken to determine the subliquidus miscibility gap and liquidus curve data. Glasses were formulated by varying the concentrations of MgF2, CaO, Al2O3 and SiO2 within the ranges specified above at fixed levels of Fe2O3, B2O3 and Na2O. The miscibility gap and liquidus curve were obtained by heat-treating the glass samples at different temperatures and observing any phase separation and crystallization in the SEM and the Transmission Electron Microscope (TEM). We report here the results of this study to enhance the understanding of the thermodynamic properties of multi-component silicate systems which are usually the basis of nuclear waste glasses.

scholarly journals Nucleation of {1012} Twins in Magnesium through Reversible Martensitic Phase Transformation

Metals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 1030
Author(s):  
Jamie Ombogo ◽  
Amir Hassan Zahiri ◽  
Tengfei Ma ◽  
Lei Cao
Keyword(s):  
Phase Transformation ◽  
Phase Transformations ◽  
Tetragonal Phase ◽  
Metastable Phase ◽  
Critical Role ◽  
Martensitic Phase ◽  
Growth Speed ◽  
Orientation Relations ◽  
Martensitic Phase Transformations ◽  
Dynamics Simulations

We report the discovery of a rigorous nucleation mechanism for {101¯2} twins in hexagonal close-packed (hcp) magnesium through reversible hcp-tetragonal-hcp martensitic phase transformations with a metastable tetragonal phase as the intermediate state. Specifically, the parent hcp phase first transforms to a metastable tetragonal phase, which subsequently transforms to a twinned hcp phase. The evanescent nature of the tetragonal phase severely hinders its direct observation, while our carefully designed molecular dynamics simulations rigorously reveal the critical role of this metastable phase in the nucleation of {101¯2} twins in magnesium. Moreover, we prove that the reversible hcp-tetragonal-hcp phase transformations involved in the twinning process follow strict orientation relations between the parent hcp, intermediate tetragonal, and twin hcp phases. This phase transformation-mediated twinning mechanism is naturally compatible with the ultrafast twin growth speed. This work will be important for a better understanding of the twinning mechanism and thus the development of novel strategies for enhancing the ductility of magnesium alloys.

Phase Transformation In Ti-6al-4v Alloys

1972 ◽  
Vol 30 ◽  
pp. 584-585
Author(s):  
Shiro Fujishiro
Keyword(s):  
Phase Transformation ◽  
Grain Boundary ◽  
Cryogenic Temperature ◽  
Β Phase ◽  
Heat Treated ◽  
Mixed Microstructure ◽  
Ductile Behavior

The Ti-6 wt.% Al-4 wt.% V commercial alloys have exhibited an improved formability at cryogenic temperature when the alloys were heat-treated prior to the tests. The author was interested in further investigating this unusual ductile behavior which may be associated with the strain-induced transformation or twinning of the a phase, enhanced at lower temperatures. The starting materials, supplied by RMI Co., Niles, Ohio were rolled mill products in the form of 40 mil sheets. The microstructure of the as-received materials contained mainly ellipsoidal α grains measuring between 1 and 5μ. The β phase formed an undefined grain boundary around the a grains. The specimens were homogenized at 1050°C for one hour, followed by aging at 500°C for two hours, and then quenched in water to produce the α/β mixed microstructure.

AMPCO 940 and AMPCO-TRODE 940

Alloy Digest ◽  
1993 ◽  
Vol 42 (3) ◽  
Keyword(s):  
Copper Alloys ◽  
Heat Treating ◽  
Resistance Welding ◽  
Chromium Alloy ◽  
Heat Treated ◽  
Association Class ◽  
Potential Applications ◽  
Minimum Requirements ◽  
Nickel Silicon ◽  
Plastic Injection

Abstract AMPCO 940 is a precipitation-hardening copper-nickel-silicon-chromium alloy developed for resistance welding and other applications now using the 1% beryllium-copper alloys. The heat-treated alloy is capable of meeting the RWMA (Resistance Welder Manufacturers Association) Class 3 minimum requirements-95,000 psi tensile strength, 90 Rockwell B hardness and 45% IACS electrical conductivity. Potential applications include resistance welding tips, wheels and fixtures. A major use is in plastic injection molding. AMPCO-TRODE 940 is used for repair welding and overlays. This datasheet provides information on composition, physical properties, hardness, and tensile properties. It also includes information on high temperature performance and corrosion resistance as well as casting, forming, heat treating, machining, and joining. Filing Code: CU-434. Producer or source: Ampco Metal Inc. Originally published as Ampcoloy 940, April 1982, revised March 1993.

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