Structural Evolution of Al-Cr Alloy during Processing

2008 ◽  
Vol 138 ◽  
pp. 145-152 ◽  
Author(s):  
Dalibor Vojtěch ◽  
Alena Michalcová ◽  
Pavel Novák
Keyword(s):  
Heat Treatment ◽  
Solid Solution ◽  
Phase Transformations ◽  
Elevated Temperatures ◽  
Supersaturated Solid Solution ◽  
Structural Evolution ◽  
Hot Extrusion ◽  
Light Components ◽  
Rapidly Solidified

Aluminium-chromium based alloys are promising candidates for manufacture of light components exposed to elevated temperatures. The work describes properties of Al-6.0wt.%Cr- 2.1wt.%Fe-0.5wt.%Ti alloy. The rapidly solidified powder was prepared by the pressure nitrogen melt atomization. The powder was then subject to heat treatment in order to investigate solid state phase transformations. Compaction of the powder was carried out by hot extrusion after preheating at 450 °C. Microstructure, phase composition and structural transformations on heat treatment were investigated in the as-atomized powder, as well as in the as-extruded alloy. It is found that metastable state of the rapidly solidified powder is characterized by presence of quasi-crystalline phases and supersaturated solid solution. Heating before and during the hot extrusion induces decomposition of the supersaturated solid solution and quasicrystalline to crystalline phase transformations. The hot extruded alloy has a refined recrystallized structure that remains very stable aven after long-term annealing at 400 °C. Mechanical properties of the extruded alloy are discussed in terms of strengthening mechanisms.

High-Temperature Instability of A Cr2Nb-Nb(Cr) Microlaminate Composite

1996 ◽  
Vol 54 ◽  
pp. 374-375
Author(s):  
M. Larsen ◽  
R.G. Rowe ◽  
D.W. Skelly
Keyword(s):  
Heat Treatment ◽  
Solid Solution ◽  
High Temperature ◽  
Elevated Temperatures ◽  
Aircraft Engine ◽  
Lattice Parameter ◽  
Microstructural Stability ◽  
Elevated Temperature Strength ◽  
Cross Sectional ◽  
Bcc Structure

Microlaminate composites consisting of alternating layers of a high temperature intermetallic compound for elevated temperature strength and a ductile refractory metal for toughening may have uses in aircraft engine turbines. Microstructural stability at elevated temperatures is a crucial requirement for these composites. A microlaminate composite consisting of alternating layers of Cr2Nb and Nb(Cr) was produced by vapor phase deposition. The stability of the layers at elevated temperatures was investigated by cross-sectional TEM.The as-deposited composite consists of layers of a Nb(Cr) solid solution with a composition in atomic percent of 91% Nb and 9% Cr. It has a bcc structure with highly elongated grains. Alternating with this Nb(Cr) layer is the Cr2Nb layer. However, this layer has deposited as a fine grain Cr(Nb) solid solution with a metastable bcc structure and a lattice parameter about half way between that of pure Nb and pure Cr. The atomic composition of this layer is 60% Cr and 40% Nb. The interface between the layers in the as-deposited condition appears very flat (figure 1). After a two hour, 1200 °C heat treatment, the metastable Cr(Nb) layer transforms to the Cr2Nb phase with the C15 cubic structure. Grain coarsening occurs in the Nb(Cr) layer and the interface between the layers roughen. The roughening of the interface is a prelude to an instability of the interface at higher heat treatment temperatures with perturbations of the Cr2Nb grains penetrating into the Nb(Cr) layer.

Microstructures of Rapidly Solidified Hypereutectic Al-Si Alloy with Low-Titanium Content

2008 ◽  
Vol 575-578 ◽  
pp. 27-31
Author(s):  
Ai Qin Wang ◽  
Jing Pei Xie ◽  
Zhong Xia Liu ◽  
Ji Wen Li ◽  
Wen Yan Wang ◽  
...  
Keyword(s):  
Solid Solution ◽  
Melt Spinning ◽  
Supersaturated Solid Solution ◽  
Primary Silicon ◽  
Titanium Content ◽  
Nucleation And Growth ◽  
Solidification Processing ◽  
Equilibrium Solidification ◽  
Rapidly Solidified ◽  
Morphology Characteristics

In the present work, rapidly solidified alloys strips with Al-0.24Ti and Al-21Si-0.24Ti(in wt.%) were prepared by single roller melt-spinning method. The microstructures, phase and morphology characteristics of the resultant strips were characterized by means of scanning electron microscopy (SEM),transmission electric microscopy (TEM) and XRD technique. The results show that the grains have been refined after rapid solidification processing, and the micro-nanocrystalline grain are formed. The morphology characteristics can be changed. The microstructures of Al-0.24Ti alloys strip are micro-nanostructure α-Al solid solutions which are similar with granular or nodular, the corresponding SAD pattern is rings, it presents characteristic of polycrystal; Compared with equilibrium solidification, the microstructures of hypereutectic Al-Si alloy are changed obviously. They are composed of primary micro-nanostructure α-Al supersaturated solid solution and nanocrystal granular (α+Si) eutectic which set in the supersaturated solid solution. The nucleation and growth of primary silicon are suppressed and primary silicon can not precipitate, meanwhile, α-Al phase is nucleated which prior to eutectic, therefore the microstructures become into the metastable state. The mechanism of the formation for microstructures of melt-spinning alloys has also been discussed.

scholarly journals MICROSTRUCTURE AND THERMAL STABILITY OF Al-Fe-X ALLOYS

2018 ◽  
Vol 24 (3) ◽  
pp. 223 ◽  
Author(s):  
Andrea Školáková ◽  
Petra Hanusová ◽  
Filip Průša ◽  
Pavel Salvetr ◽  
Pavel Novák ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Melt Spinning ◽  
Hot Extrusion ◽  
Dispersed Particles ◽  
Cast Alloys ◽  
Rapidly Solidified ◽  
Thermal Stability Of ◽  
Melt Spinning Technique ◽  
Extrusion Method

<p>In this work, Al-11Fe, Al-7Fe-4Ni and Al-7Fe-4Cr (in wt. %) alloys were prepared by combination of casting and hot extrusion. Microstructures of as-cast alloys were composed of aluminium matrix with large and coarse intermetallics such as Al<sub>13</sub>Fe<sub>4</sub>, Al<sub>13</sub>Cr<sub>2</sub> and Al<sub>5</sub>Cr. Subsequently, as-cast alloys were rapidly solidified by melt-spinning technique which led to the supersaturation of solid solution alloying elements. These rapidly solidified ribbons were milled and compacted by hot-extrusion method. Hot-extrusion caused that microstructures of all alloys were fine with uniform dispersed particles. Moreover, long-term thermal stability was tested at temperature 300 °C for as-cast and hot-extruded alloys and chromium was found to be the most suitable element for alloying to improve thermal stability.    </p>

The Microstructural Peculiarities of Beryllium Bronze after Heat Treatment

2020 ◽  
Vol 989 ◽  
pp. 172-176
Author(s):  
V.R. Baraz ◽  
S.X. Estemirova ◽  
E.A. Ishina
Keyword(s):  
Heat Treatment ◽  
Solid Solution ◽  
Supersaturated Solid Solution ◽  
Strength Properties ◽  
Micro Hardness ◽  
Beryllium Bronze ◽  
Phase Type ◽  
Solid Solution Matrix ◽  
Χ Phase ◽  
Solution Matrix

In this article, the microstructural peculiarities and properties of dispersion-hardened beryllium bronze with Ni and Ti are studied after quenching (780 °C) in a supersaturated solid solution and aging (320 °C, 3h). Decomposition of the α-solid solution matrix is implemented by means of an intermittent reaction with a primary allocation intermetallic χ-phase (type Be12Ti) with a VCT-lattice. It is shown that the strength properties (yield strength, micro-hardness) of the alloy more than double after aging.

The Effect of Heat Treatment and Mn, Cu and Cr Additions on the Structure of Ingots of Al-Mg-Si-Fe Alloys

2006 ◽  
Vol 519-521 ◽  
pp. 401-406 ◽  
Author(s):  
P.Yu. Bryantsev ◽  
V.S. Zolotorevskiy ◽  
V.K. Portnoy
Keyword(s):  
Heat Treatment ◽  
Solid Solution ◽  
Phase Transformations ◽  
Cooling Rate ◽  
Homogenization Temperature ◽  
Decomposition Of Solid Solution ◽  
Different Temperatures ◽  
Continuous Cooling Transformation Diagrams ◽  
Fe Alloys ◽  
Transformation Diagrams

Phase transformations in 6XXX alloys with Mn, Cu and Cr additions have been studied in the process of homogenization annealing at different temperatures. The continuous cooling transformation diagrams of decomposition of solid solution during the cooling of ingots from the homogenization temperature have been plotted. The effect of the cooling rate after homogenization on the properties of ingots during extrusion has been studied.

Microstructures and Mechanical Properties of NiAl+Mo In-Situ Eutectic Composites

1990 ◽  
Vol 194 ◽  
Author(s):  
P. R. Subramanian ◽  
M. G. Mendiratta ◽  
D. B. Miracle ◽  
D. M. Dimiduk
Keyword(s):  
Mechanical Properties ◽  
Solid Solution ◽  
Room Temperature ◽  
Composite System ◽  
Elevated Temperatures ◽  
Two Phase ◽  
Structural Applications ◽  
Temperature Fracture

AbstractThe quasibinary NiAI-Mo system exhibits a large two-phase field between NiAl and the terminal (Mo) solid solution, and offers the potential for producing in-situ eutectic composites for high-temperature structural applications. The phase stability of this composite system was experimentally evaluated, following long-term exposures at elevated temperatures. Bend strengths as a function of temperature and room-temperature fracture toughness data are presented for selected NiA1-Mo alloys, together with results from fractography observations.

Effect of Mg Addition on the Mechanical Properties of Rapidly Solidified Al-Mn Alloys at Elevated Temperatures

2010 ◽  
Vol 638-642 ◽  
pp. 339-344
Author(s):  
Makoto Sugamata ◽  
Akio Tomioka ◽  
Yousuke Kubota
Keyword(s):  
Mechanical Properties ◽  
Solid Solution ◽  
Tensile Strength ◽  
Intermetallic Compounds ◽  
Elevated Temperatures ◽  
Optical Microscope ◽  
Strength Increase ◽  
Positive Effects ◽  
Uniform Dispersion ◽  
Rapidly Solidified

With an aim of clarifying the strength of rapidly solidified P/M materials strengthened by solid solution of Mg and dispersion of transition metal compounds at elevated temperature, Al-2mass%Mn, Al-4mass%Mn and Al-6mass%Mn alloys with varied Mg additions of 0, 1 and 3 mass% were prepared by rapid solidification techniques. Rapidly solidified (RS) flakes were produced by remelting alloy ingots in a graphite crucible, atomizing the alloy melt and subsequent splat-quenching on a rotating water-cooled copper roll under argon atmosphere.　The RS flakes were consolidated to the P/M materials by hot extrusion after vacuum degassing. Cast ingots of these alloys were also hot-extruded under the same conditions to the I/M as reference materials. Metallographic structures and constituent phases were studied for the P/M and I/M materials by optical microscope and X-ray diffraction. Mechanical properties of as-extruded and annealed P/M materials and as-extruded I/M materials were examined by tensile test at room and elevated temperatures under various strain rates. Uniform dispersion of fine intermetallic compounds (Al6Mn) was observed in all the as-extruded P/M materials. Added Mg was present as the solute in I/M and P/M materials alloy even after annealing. The P/M materials containing Mg exhibited higher hardness and strength at room temperature, than those without Mg. It was considered that both solid solution of Mg and dispersion of intermetallic compounds were contributing the hardness and strength increase in the rapidly solidified Al-Mn-Mg alloys. Tensile strength increases with increasing amount of Mg in I/M materials at all testing temperatures. However, strength of as-extruded P/M materials decreases with addition of Mg at 573K and 673K. Thus the positive effects of Mg additions on tensile strength of as-extruded P/M materials disappeared at higher testing temperature. Tensile strength of annealed P/M materials in which dislocation density decreased and compound particle coarsened increased with addition of Mg at elevated temperatures.

Thermal Stability Study of Ce0.75-Zr0.25O Nanostructures Synthesized via Water-in-Oil Microemulsion Method

2013 ◽  
Vol 701 ◽  
pp. 207-211 ◽  
Author(s):  
Nur Azrani M. Jani ◽  
Abdul Hadi ◽  
Kamariah Noor Ismail
Keyword(s):  
Heat Treatment ◽  
Thermal Stability ◽  
Solid Solution ◽  
Elevated Temperatures ◽  
Xrd Analysis ◽  
Oxygen Storage ◽  
Microemulsion Method ◽  
Surface Areas ◽  
Wide Range ◽  
Three Way Catalyst

Fundamentally, ceria particle had ability to store, transport and release oxygen, which was identified as oxygen storage capacity (OSC). Due to this OSC ability, ceria became the most important component in the three-way catalyst. With the addition of zirconia into the ceria resulting in better performance in three-way catalyst as it increased or improved thermal stability and also promotes the redox properties. This study was conducted to investigate the effects of heat treatment on the structure and physical property of nanocrystalline Ce-Zr-O solid solution. Microemulsion method was used for preparation of Ce-Zr-O solid solution, and heat treatment investigation was applied towards the synthesized nanocrystalline Ce-Zr-O solid solution. The phase and crystal structure of Ce-Zr-O solid solution were determined using XRD analysis. While, the modification of surface area and porosity size over the wide range of calcination temperatures range from 300°C to 700°C was investigated using BET Analyzer. XRD analysis confirmed the Ce0.75Zr0.25O2 solid solution was succesfully synthesized in the research. The results exhibited the effect of heat treatment on the decreasing of surface areas and porosity profiles of the Ce0.75Zr0.25O2. Despite of the reduction of surface areas at elevated temperatures, the study found the promising results that the enhancement of thermal stability of ceria by addition of zirconia.

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