scholarly journals Understanding the Thermodynamics and Crystal Structure of Complex Fe Containing Intermetallic Phases Formed on Solidification of Aluminium Alloys

JOM ◽  
2019 ◽  
Vol 71 (5) ◽  
pp. 1731-1736 ◽  
Author(s):  
Alan Dinsdale ◽  
Changming Fang ◽  
Zhongping Que ◽  
Zhongyun Fan
Keyword(s):  
Crystal Structure ◽  
Aluminium Alloys ◽  
Intermetallic Phases

The Failure Degradation of Recycled Aluminium Alloys with High Content of β-Al5FeSi Intermetallic Phases

2020 ◽  
Vol 403 ◽  
pp. 97-102
Author(s):  
Denisa Medvecká ◽  
Lenka Kuchariková ◽  
Milan Uhríčik
Keyword(s):  
Aluminium Alloys ◽  
Cast Alloy ◽  
Intermetallic Phases ◽  
X Ray ◽  
Fracture Surfaces ◽  
Phase Lead ◽  
Micro Cracks ◽  
Fe Content ◽  
Increased Risk ◽  
Cast Alloys

In this study, the effect of the β-Al5FeSi phases on fracture surfaces in secondary AlSi7Mg0.3 cast alloys with common and higher amount of iron was investigated. Iron addition caused the formation of different Fe-rich intermetallic phases in aluminium alloys. Components made of secondary aluminium alloys commonly have a higher amount of such phases. Sharp needles as β-Al5FeSi phase lead to initiate stress tension, thereby contributing to increased risk of micro-cracks formation on the fracture surfaces. To determine the effect of β-Al5FeSi to fracture surfaces of AlSi7Mg0.3 cast alloy, SEM microscopy with energy-dispersive X-ray spectroscopy (EDX) was used to study the amount of needles phases, their morphology and violation wave. It was found that increasing Fe content increased the size and the number of Al5FeSi phases. The fractographic analysis of fracture surfaces shows an increasing amount of cleavage fracture in materials with a higher amount of iron, too.

Interface Related Strength Phenomena in Two-Phase Titanium Aluminides

1999 ◽  
Vol 586 ◽  
Author(s):  
U. Christoph ◽  
M. Oehring ◽  
F. Appel
Keyword(s):  
Crystal Structure ◽  
Electron Microscope ◽  
Microscope Study ◽  
Lamellar Structure ◽  
Electron Microscope Study ◽  
Titanium Aluminides ◽  
Intermetallic Phases ◽  
Dislocation Loops ◽  
Two Phase ◽  
Interfacial Dislocations

ABSTRACTPhase equilibria and transformations in near-equiatomic titanium aluminides lead to the formation of a lamellar structure comprising of the intermetallic phases α2(Ti3Al) and γ(TiAl). Due to the differences in lattice parameters and crystal structure, coherency stresses and mismatch structures occur at various types of semicoherent interfaces present in the material. The present paper reports an electron microscope study of the atomic structure of the interfaces. The residual coherency stresses present at the interfaces were determined by analysing the curvature of dislocation loops which were emitted from the network of interfacial dislocations. The implication of these stresses on creep will be discussed.

scholarly journals The new phase GdFe0690Si1940as a structural intermediate of GdSi2and GdFe2Si2

2014 ◽  
Vol 70 (a1) ◽  
pp. C1776-C1776
Author(s):  
Anastasiya Vinokur ◽  
Daniel Fredrickson
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Crystal Structures ◽  
Driving Forces ◽  
Intermetallic Phases ◽  
Intermediate Point ◽  
Structural Variety ◽  
Common Structure ◽  
Fe Content ◽  
New Phase

Intermetallic phases are solid state compounds formed between metals that exhibit a wide structural variety and a myriad of important properties such as magnetism, catalysis, and superconductivity. Developing their properties requires an ability to control or guide their crystal structures, which can be wildly elaborate, involving thousands of atoms per unit cell. One principle for approaching this problem is the recognition that many of the most complex phases encountered in intermetallics can be understood in terms of fragments of simpler structures. The challenge of tailoring of intermetallics then lies in understanding the driving forces for the insertion of interfaces into simple structures to build complexity. We present the synthesis and the crystal structure of a new phase that sheds light on this issue, GdFe0690Si1940. It shares structural motifs with two neighboring phases in the Gd-Fe-Si system with common structure types, GdSi2(AlB2-type) and GdFe2Si2(ThCr2Si2-type). GdFe0690Si1940arises as the hexagonal nets of GdSi2are cut perpendicular to the a axis by square nets, forming distinct slabs. The surroundings of the Fe square nets locally resemble slabs of the GdFe2Si2structure, but the Fe content of the nets varies, depending on the presence of an Fe/Si mixed site. GdFe0690Si1940thus represents an intermediate point between the GdSi2and GdFe2Si2phases. This viewpoint offers the possibility of a series of crystal structures linking GdSi2and GdFe2Si2, representing a continuum of GdFexSi2phases with varying degrees of Fe incorporation, which we are now exploring synthetically.

scholarly journals On intermetallic phases formed during interdiffusion between aluminium alloys and stainless steel

2022 ◽  
Vol 142 ◽  
pp. 107443
Author(s):  
Tina Bergh ◽  
Siri Marthe Arbo ◽  
Anette Brocks Hagen ◽  
Jørgen Blindheim ◽  
Jesper Friis ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Aluminium Alloys ◽  
Intermetallic Phases

scholarly journals Passive Film Properties of Bimodal Grain Size AA7075 Aluminium Alloy Prepared by Spark Plasma Sintering

Materials ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3236
Author(s):  
Wenming Tian ◽  
Zhonglei Li ◽  
HuiFeng Kang ◽  
Fasong Cheng ◽  
Fangfang Chen ◽  
...  
Keyword(s):  
Passive Film ◽  
Aluminium Alloys ◽  
Defect Density ◽  
Intermetallic Phases ◽  
Coarse Grain ◽  
Fine Grain ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Sintered Alloys ◽  
Bimodal Grain Size

The bimodal-grain-size 7075 aluminium alloys containing varied ratios of large and small 7075 aluminium powders were prepared by spark plasma sintering (SPS). The large powder was 100 ± 15 μm in diameter and the small one was 10 ± 5 μm in diameter. The 7075 aluminium alloys was completely densified under the 500 °C sintering temperature and 60 MPa pressure. The large powders constituted coarse grain zone, and the small powders constituted fine grain zone in sintered 7075 aluminium alloys. The microstructural and microchemical difference between the large and small powders was remained in coarse and fine grain zones in bulk alloys after SPS sintering, which allowed for us to investigate the effects of microstructure and microchemistry on passive properties of oxide film formed on sintered alloys. The average diameter of intermetallic phases was 201.3 nm in coarse grain zone, while its vale was 79.8 nm in fine grain zone. The alloying element content in intermetallic phases in coarse grain zone was 33% to 48% higher than that on fine grain zone. The alloying element depletion zone surrounding intermetallic phases in coarse grain zone showed a bigger width and a more severe element depletion. The coarse grain zone in alloys showed a bigger electrochemical heterogeneity as compared to fine grain zone. The passive film formed on coarse grain zone had a thicker thickness and a point defect density of 2.4 × 1024 m−3, and the film on fine grain zone had a thinner thickness and a point defect density of 4.0 × 1023 m−3. The film resistance was 3.25 × 105 Ωcm2 on coarse grain zone, while it was 6.46 × 105 Ωcm2 on fine grain zone. The passive potential range of sintered alloys increased from 457 mV to 678 mV, while the corrosion current density decreased from 8.59 × 10−7 A/cm2 to 6.78 × 10−7 A/cm2 as fine grain zone increasing from 0% to 100%, which implied that the corrosion resistance of alloys increased with the increasing content of fine grains. The passive film on coarse grain zone exhibited bigger corrosion cavities after pitting initiation compared to that on fine grain zone. The passive film formed on fine grain zone showed a better corrosion resistance. The protectiveness of passive film was mainly determined by defect density rather than the thickness in this work.

Dispersoid Phases in 6xxx Series Aluminium Alloys

2010 ◽  
Vol 654-656 ◽  
pp. 926-929 ◽  
Author(s):  
Katharina Strobel ◽  
Elizabeth Sweet ◽  
Mark Easton ◽  
Jian Feng Nie ◽  
Malcolm Couper
Keyword(s):  
Crystal Structure ◽  
Fracture Toughness ◽  
Chemical Composition ◽  
Aluminium Alloys ◽  
Alloy Composition ◽  
High Strength ◽  
Grain Structure ◽  
Improve Fracture Toughness ◽  
And Control ◽  
6Xxx Series

In high strength AlMgSi alloys additions of Mn and Cr lead to the formation of dispersoid phases whose primary functions are to improve fracture toughness and control grain structure. Whether or not dispersoid phases form during heating to the homogenisation temperature and which dispersoid forms is strongly dependent on the alloy composition. By correlating dispersoid features after different homogenisation heat treatments to TEM investigations into the crystal structure, it is proposed that the crystal structure and chemical composition of the dispersoids changes as the dispersoids coarsen at increased temperatures and times.

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