The Effect of Ge and Ti Additions on the Microstructures and Properties of Nb-18Si Based Alloys

2011 ◽  
Vol 1295 ◽  
Author(s):  
Zifu Li ◽  
Panos Tsakiropoulos
Keyword(s):  
Heat Treatment ◽  
Solid Solution ◽  
Oxidation Resistance ◽  
Cast Alloy ◽  
High Volume ◽  
Primary Phase ◽  
Oxidation Behaviour ◽  
Volume Fractions ◽  
Two Phases ◽  
Cast Microstructure

ABSTRACTThe effects of Ge and Ti additions on the microstructure, hardness and oxidation behaviour of the alloys Nb–18Si–5Ge (ZF1) and Nb–24Ti–18Si–5Ge (ZF3) were studied. The as cast microstructure of the alloy ZF1 consisted of Nbss (cI2), and βNb5Si3 (tI32) with the latter being the primary phase and the two phases forming high volume fractions of Nbss + βNb5Si3 eutectic. The Ge addition stabilised the βNb5Si3 (tI32), and destabilised the Nb3Si (tP32) and the Nbss + Nb3Si eutectic. After heat treatment at 1200 °C for 100 h the βNb5Si3 (tI32) was partially transformed to the αNb5Si3 (tI32), and equilibrium was reached after heat treatment at 1500 °C for 100 h. The phases present in the as cast alloy ZF3 were the Nbss (cI2), and the Nb3Si (tP32), βNb5Si3 (tI32) and Ti5Si3 (hP16) silicides, with the latter forming a eutectic with the solid solution. The same phases were present after heat treatment at 1200 °C for 100 h but only the Nbss, and the Nb3Si and Nb5Si3 silicides were present after 100 h at 1500 °C where TiO2 was also formed. The Ge addition increased the microhardness of the Nb5Si3. The synergy of Ti with Ge resulted in a strong hardening effect and a remarkable retention of the hardness of the alloy ZF3. The additions of Ge and Ti to the Nb-18Si alloy improved the oxidation resistance at 800 °C, but pest oxidation behaviour was not eliminated.

Microstructure in Rapidly Quenched Al-Ti,Al-B and Al-Ti-B Alloys

1986 ◽  
Vol 80 ◽  
Author(s):  
A. Majumdar ◽  
R. H. Mair ◽  
B. C. Muddle
Keyword(s):  
Heat Treatment ◽  
Solid Solution ◽  
Melt Spinning ◽  
Analytical Electron Microscopy ◽  
Primary Phase ◽  
Nucleation Sites ◽  
Uniform Dispersion ◽  
Average Grain Size ◽  
Melt Spun ◽  
Chill Cast

AbstractRapidly quenched ribbons (˜50m thickness) of Al-5wt.%Ti, Al-lwt.%B and a range of Al-Ti-B alloys have been produced by melt spinning under He atmosphere and the microstructures of the ribbons, following solidification and post-solidification heat treatment, characterized using analytical electron microscopy. In the Al-5Ti alloy, the coarse equilibrium primary phase (b.c.t. Al3 Ti) that is observed following conventional casting is replaced by fine (0.1–0. 2μm), cuboidal particles of a metastable cubic (Ll2) Al3Ti in melt-spun ribbon. These metastable particles form directly from the melt and act as nucleation sites for the solid solution which subsequently forms. A refined microstructure with an average grain size of 1–2μm results. A supersaturation of Ti is retained in matrix solid solution following solidification and a variety of solid state precipitate forms, including fine dispersions of coherent, metastable Al3 Ti particles, is observed to emerge during post-solidification heat treatment. For the Al-1B alloy, the coarse distribution of primary AlB2 particles in a chill-cast ingot is replaced by a fine, uniform dispersion of the metastable boride, α-AlB12, in the melt-spun ribbon. Attempts to induce a refined boride dispersion in melt-spun Al-Ti-B alloys have proved largely unsuccessful.

scholarly journals On the Microstructure and Isothermal Oxidation at 800 and 1200 °C of the Nb-24Ti-18Si-5Al-5Cr-5Ge-5Sn (at.%) Silicide-Based Alloy

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 722 ◽  
Author(s):  
Ofelia Hernández-Negrete ◽  
Panos Tsakiropoulos
Keyword(s):  
Solid Solution ◽  
Oxidation Resistance ◽  
Volume Fraction ◽  
Coefficient Of Thermal Expansion ◽  
Cast Alloy ◽  
Isothermal Oxidation ◽  
Valence Electron Concentration ◽  
Scale Spallation ◽  
Substrate Interface ◽  
Oxidation In Air

The research presented in this paper aspired to understand how the simultaneous addition of Ge and Sn in an Hf-free Nb-silicide-based alloy affected its oxidation resistance. Results are presented for the Nb-24Ti-18Si-5Al-5Cr-5Ge-5Sn alloy (at.%) which was studied in the as-cast and heat-treated (1400 °C/100 h) conditions and after isothermal oxidation in air at 800 and 1200 °C. There was macrosegregation in the cast alloy, in which the Nbss formed at a low volume fraction and was not stable after heat treatment at 1400 °C. The βNb5Si3, A15-Nb3Sn, and C14-NbCr2 were stable phases. The alloy did not undergo pest oxidation at 800 °C, and there was no spallation of its scale at 1200 °C. There was enrichment in Ge and Sn in the substrate below the scale/substrate interface, where the compounds Nb3Sn, Nb5Sn2Si, (Ti,Nb)6Sn5, and Nb5Ge3 were formed. After the oxidation at 1200 °C, the solid solution in the bulk of the alloy was very Ti-rich (Ti,Nb)ss. Improvement of oxidation resistance at both temperatures was accompanied by a decrease and increase, respectively, of the alloy parameters VEC (valence electron concentration) and δ, in agreement with the alloy design methodology NICE (Niobium Intermetallic Composite Elaboration). The elimination of scale spallation at 1200 °C was attributed (a) to the formation of Ti-rich (Ti,Nb)ss solid solution and (Ti,Nb)6Sn5, respectively, in the bulk and below the scale, (b) to the low concentration of Cr in the scale, (c) to the absence of GeO2 in the scale, (d) to the formation of αAl2O3 in the scale, and (e) to the presence (i) of Nb5Ge3 below the scale/substrate interface and (ii) of oxides in the scale, namely, SiO2, Al2O3, TiO2, and SnO2, and Ti2Nb10O29,TiNb2O7, and AlNbO4, respectively, with a range of intrinsic thermal shock resistances and coefficient of thermal expansion (CTE) values that reduced stresses in the scale and the substrate below it.

scholarly journals Investigation of the Effect of Heat Treatment on the Microstructures and Mechanical Properties of Al-13Si-5Cu-2Ni Alloy

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 688
Author(s):  
Zhi-Fa Wang ◽  
Tian-Jing Miao ◽  
Shu-Qing Kou ◽  
Shuang Zhang ◽  
Feng Qiu
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Solid Solution ◽  
Cast Alloy ◽  
Eutectic Silicon ◽  
Solution Treatment ◽  
Aging Treatment ◽  
Solution Treatment Temperature ◽  
Solid Solution Treatment ◽  
Microstructures And Mechanical Properties

An experimental investigation was carried out to study the effects of solid solution treatment and aging treatment on the microstructures and mechanical properties of an Al-13Si-5Cu-2Ni alloy. The results show that the size of eutectic silicon decreased with solid solution treatment temperature increasing until 510 °C. Subsequently, the eutectic silicon size continued to increase as the temperature increased to 520 °C. Initially, the acicular eutectic silicon of the as-cast alloy was 10.1 μm in size. After the solid solution treatment at 510 °C, the eutectic silicon size was reduced to 6.5 μm. The θ′ phase is the main strengthening phase in the alloy, therefore, the effect of aging treatment on θ′ phases was explored. As the aging time increased, the diameter, length, and fraction volume of the θ′ phases were found to increase. The main reason for the improved performance of this alloy following heat treatment is the passivation spheroidization of the silicon phase and Orowan strengthening due to the θ′ phases. The optimal tensile strength of an Al-13Si-5Cu-2Ni alloy was obtained after solid solution treatment at 510 °C for 8 h followed by an aging treatment at 165 °C for 8 h. Therefore, this work has great significance for promoting the application of Al alloys at high temperatures.

TEM Investigations of Electron 21 Magnesium Alloy

2007 ◽  
Vol 130 ◽  
pp. 175-180 ◽  
Author(s):  
Andrzej Kiełbus
Keyword(s):  
Heat Treatment ◽  
Magnesium Alloy ◽  
Solution Heat Treatment ◽  
Cast Alloy ◽  
Solution Treatment ◽  
Air Cooling ◽  
Transmission Electron ◽  
The Matrix ◽  
Cast Condition ◽  
Cast Microstructure

The paper presents results of TEM investigations of Elektron 21 magnesium alloy in as cast condition and after heat treatment. The compositions of the Elektron 21 alloy used in the present study was Mg-2,7%wtNd-1,2%wtGd-0,47%wtZr. Solution heat treatment was performed at 520°C/8 h/water. Ageing treatments were performed at 200°C/4÷96h and 300°C/48h with cooling in air. The as-cast microstructure and microstructural evolution during heat treatment were examined by transmission electron microscopy. Samples were prepared using Gatan PIPS ion mill. Examinations were performed in a JEM 2010 ARP microscope. The microstructure of the cast alloy consists of a-Mg phase matrix with precipitates of Mg12(Ndx,Gd1-x) phase at grain boundaries. After solution treatment the Mg12(Ndx,Gd1-x) phase dissolved in the matrix. The ageing treatment applied after solution treatment with air-cooling caused precipitation of a β’ and β phases.

Optimization of Mo-Si-B Intermetallics

2002 ◽  
Vol 753 ◽  
Author(s):  
Joachim H. Schneibel ◽  
Peter F. Tortorelli ◽  
Matthew J. Kramer ◽  
Andrew J. Thom ◽  
Jamie J. Kruzic ◽  
...  
Keyword(s):  
Solid Solution ◽  
Fracture Toughness ◽  
Oxidation Resistance ◽  
Creep Strength ◽  
Length Scale ◽  
Phase Volume ◽  
Volume Fractions ◽  
Degree Of Oxidation

ABSTRACTMo-Si-B intermetallics consisting of the phases Mo3Si, Mo5SiB2, and α-Mo (Mo solid solution) can be designed to exhibit some degree of oxidation resistance, fracture toughness, and creep strength, but not necessarily all of these at the same time. For example, microstructures that enhance the oxidation resistance are typically associated with low fracture toughness. Examples will be given illustrating the oxidation resistance, fracture toughness, and creep strength of Mo-Si-B intermetallics as a function of their phase volume fractions as well as the topology and length scale of their microstructures. Microstructures containing either individual α-Mo particles or a continuous α-Mo matrix will be described. The examples provide possible ways to control the composition and microstructure of Mo-Si-B alloys such as to optimize the desired balance of properties.

Improved Corrosion Resistance of Superheater Materials in H2O Containing Environments Using Mn-Diffusion Coatings

2011 ◽  
Vol 696 ◽  
pp. 330-335 ◽  
Author(s):  
Diana Schmidt ◽  
Michael Schütze
Keyword(s):  
Heat Treatment ◽  
Corrosion Resistance ◽  
Water Vapour ◽  
Oxidation Resistance ◽  
Electrochemical Deposition ◽  
Vapour Pressure ◽  
Oxidation Behaviour ◽  
Chromium Species ◽  
Diffusion Coatings ◽  
Mn Diffusion

The oxidation resistance of ferritic-martensitic 9% chromium steels in water vapour containing atmospheres is not yet satisfactory. The chromia layer provides little protection because water vapour in the atmosphere is known to promote the formation of the volatile chromium species CrO2(OH)2. If a chromium manganese spinel is formed instead, the vapour pressure of the oxy-hydroxide is greatly reduced and evaporation can largely be avoided. Enrichment of the substrate with manganese was achieved using three different processes: using (i) a sputtering technique, (ii) electrochemical deposition both followed by a diffusion heat treatment, (iii) the pack cementation method. Uniform diffusion of manganese was obtained with all of the investigated processes. The improved oxidation behaviour of the coated samples in synthetic air with 10% water vapour at 650°C was demonstrated.

The Effect of Homogenization on the Annealing of Al-1,5%Mn Aluminium Alloy

2013 ◽  
Vol 752 ◽  
pp. 193-197 ◽  
Author(s):  
Tibor Hegyes ◽  
Peter Barkoczy
Keyword(s):  
Heat Treatment ◽  
Solid Solution ◽  
Crystallization Process ◽  
Cast Alloy ◽  
Solid Solution Phase ◽  
Degree Of Deformation ◽  
High Temperature Heat Treatment ◽  
Temperature Heat ◽  
Pre Treatment ◽  
Temperature Heat Treatment

The softening of Al-Mn base alloys not only depend on the degree of deformation and the parameters of annealing, but the pre-treatment of as-cast alloy. Large extent of the Mn remains in the solid solution during the crystallization process. During a high temperature heat treatment the manganese precipitate from the solid solution phase. The size and amount of the precipitations mainly of the processes takes place during annealing. In this article this effect is studied through the heat treatment and deformation of a specific alloy.

The Influence of Heat Treatment on the Microstructure and Hardness of Mg-5Si-7Sn-5Mn Alloy

2015 ◽  
Vol 229 ◽  
pp. 83-88
Author(s):  
Tomasz Rzychoń ◽  
Bartosz Chmiela ◽  
Adrian Mościcki ◽  
Bartłomiej Dybowski ◽  
Sylwia Jendrysko
Keyword(s):  
Heat Treatment ◽  
Solid Solution ◽  
Intermetallic Compounds ◽  
Cast Alloy ◽  
Solution Treatment ◽  
Chinese Script

The microstructure and hardness of as-cast Mg-5Si-7Sn-5Mn alloy after solution and ageing treatments is presented in this paper. It was found that the microstructure of as-cast alloy. is composed of primary dendrites crystals of Mg2Si phase, α-Mg matrix, long needle-like precipitates of Mn5Si3, Chinese script particles of Mg2Si phase and irregular Mg2Sn phase. The solution treatment at 500°C causes the dissolution of the Mg2Sn phase in the α-Mg magnesium solid solution, whereas the remaining intermetallic compounds are stable in this temperature. The hardness of alloy increases from 73 HV2 to 96 HV2 at 250°C. The increase in hardness is a result of the formation of the lath-like precipitates of Mg2Sn phase within the α-Mg matrix.

scholarly journals Influence of Solution Heat Treatment on Structure and Mechanical Properties of ZnAl22Cu3 Alloy

2016 ◽  
Vol 61 (3) ◽  
pp. 1581-1586 ◽  
Author(s):  
R. Michalik ◽  
B. Chmiela
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Solid Solution ◽  
Solution Heat Treatment ◽  
Supersaturated Solid Solution ◽  
Cast Alloy ◽  
Dendritic Structure ◽  
Alloy Hardness ◽  
Ε Phase ◽  
Phase Solution

Abstract The influence of solution heat treatment at 385°C over 10 h with cooling in water on the structure, hardness and strength of the ZnAl22Cu3 eutectoid alloy is presented in the paper. The eutectoid ZnAl22Cu3 alloy is characterized by a dendritic structure. Dendrites are composed of a supersaturated solid solution of Al in Zn. In the interdendritic spaces a eutectoid mixture is present, with an absence of the ε (CuZn4) phase. Solution heat treatment of the ZnAl22Cu3 alloy causes the occurrence of precipitates rich in Zn and Cu, possibly ε phase. Solution heat treatment at 385°C initially causes a significant decrease of the alloy hardness, although longer solution heat treatment causes a significant increase of the hardness as compared to the as-cast alloy.

Sign in / Sign up

Export Citation Format

Share Document