The rate of solidification and the effects of local composition on the subsequent nucleation of Al2Cu2Mn3 dispersoid phase in Al-4Cu-0.3Fe-0.4Mn-0.2Si alloys

Following solidification, an aluminum alloy microstructure is highly segregated. The microstructure consists of cored dendrites with various soluble and insoluble phases present in the inter-dendritic regions. The solidification rate has a marked effect on the amount of coring as well as grain dimensions and second phase particle size and spacing. Post-solidification cooling rates as well as subsequent heat treatments also affect the evolution of the microstructure. Understanding the effects of these thermal treatments is important in explaining differences in microstructures that are observed in alloys of identical compositions. The focus of this study is to determine the interaction between the coring of copper across dendrites during solidification and the precipitation of dispersoids during the homogenization treatments of an alloy. An aluminum alloy whose composition is in the range of Al-4Cu-0.3Fe-0.4Mn-0.2Si is ideally suited for this study for several reasons. First it is similar to a host of commercial aluminum copper alloys, and the presence of Mn, Fe, and Si affect the distribution of particles that control grain morphology in these alloys. Preliminary experimental results are discussed. Current numerical analysis techniques will be examined and possible methods to treat the problem will be presented.

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The Effect of Thermal Treatment on the Microstructural Evolution of an Al-Cu Alloy

Heat Transfer: Volume 3 ◽

10.1115/ht2003-47149 ◽

2003 ◽

Author(s):

Tracie L. Zoeller ◽

Thomas H. Sanders

Keyword(s):

Aluminum Alloy ◽

Chemical Composition ◽

Marked Effect ◽

Volume Fraction ◽

Solidification Rate ◽

Thermal Treatments ◽

Large Volume Fraction ◽

Cu Alloy ◽

Processing Step ◽

Alloy Microstructure

Following solidification, an aluminum alloy microstructure is highly segregated. The microstructure consists of cored dendrites with various soluble and insoluble phases present in the dendritic regions. The solidification rate has a marked effect on the amount of coring that an alloy experiences. Understanding the effects of the solidification rate is important in explaining differences in microstructures. Subsequent heat treatments are performed to homogenize the microstructure. The microstructure evolution after each processing step is dependent upon the previous microstructures. The variation in local chemical composition may promote or hinder precipitation of new phases. A large volume fraction of coarse insoluble phases can lead to the occurrence of recrystallized grains via particle stimulated nucleation, while inhomogeneous solute distribution can lead to the precipitation of an uneven distribution of dispersoid phases. The effect of solidification rate and subsequent thermal treatments on the microstructure of an Al-4Cu alloy will be investigated and experimental and numerical results will be presented.

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Orientation Mapping Study on the Inhomogeneous Microstructure Evolution during Annealing of 6013 Aluminum Alloy

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.163.13 ◽

2010 ◽

Vol 163 ◽

pp. 13-18 ◽

Cited By ~ 8

Author(s):

M. Bieda-Niemiec ◽

Krzystof Sztwiertnia ◽

A. Korneva ◽

Tomasz Czeppe ◽

R. Orlicki

Keyword(s):

Aluminum Alloy ◽

Particle Distribution ◽

Phase Particle ◽

Second Phase ◽

Transmission Electron ◽

Orientation Mapping ◽

Initial Stage ◽

Second Phase Particles ◽

Cold Rolled

Orientation mapping in transmission electron microscope was successfully applied to study microstructural changes at the initial stage of recrystallization in the aluminum alloy with a bimodal second-phase particle distribution. The alloy samples were reversibly cold rolled resulting in the formation of laminar structure with zones of localized strain around large second-phase particles. Orientation mapping and in-situ investigations carry information about the processes which are active in the deformation zones during annealing.

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Simulation of Damage Percolation Within Aluminum Alloy Sheet

Journal of Engineering Materials and Technology ◽

10.1115/1.3078389 ◽

2009 ◽

Vol 131 (2) ◽

Cited By ~ 4

Author(s):

O. S. Orlov ◽

M. J. Worswick ◽

E. Maire ◽

D. J. Lloyd

Keyword(s):

Aluminum Alloy ◽

Void Nucleation ◽

Phase Particle ◽

Three Dimensional ◽

Alloy Sheet ◽

Void Coalescence ◽

Second Phase ◽

X Ray ◽

Damage Initiation

A combined experimental and analytical approach is used to study damage initiation and evolution in three-dimensional second phase particle fields. A three-dimensional formulation of a damage percolation model is developed to predict damage nucleation and propagation through random-clustered second phase particle fields. The proposed approach is capable of capturing the three-dimensional character of damage phenomena and the three stages of ductile fracture, namely, void nucleation, growth, and coalescence, at the level of discrete particles. An in situ tensile test with X-ray tomography is utilized to quantify material damage during deformation in terms of the number of nucleated voids and porosity. The results of this experiment are used for both the development of a clustering-sensitive nucleation criterion and the validation of the damage percolation predictions. The evolution of damage in aluminum alloy AA5182 has been successfully predicted to match that in the in situ tensile specimen. Two forms of second phase particle field input data were considered: (1) that measured directly with X-ray tomography and (2) fields reconstructed statistically from two-dimensional orthogonal sections. It is demonstrated that the adoption of a cluster-sensitive void nucleation criterion, as opposed to a cluster-insensitive nucleation criterion, has a significant effect in promoting predicted void nucleation to occur within particle clusters. This behavior leads to confinement of void coalescence to within clusters for most of the duration of deformation followed by later development of a macrocrack through intracluster coalescence. The measured and reconstructed second phase particle fields lead to similar rates of predicted damage accumulation and can be used interchangeably in damage percolation simulations.

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Stability of Chemical Order in Ni4Mo Alloy under Fast Electron Irradiation

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100077864 ◽

1977 ◽

Vol 35 ◽

pp. 48-49

Author(s):

R. W. Carpenter ◽

E. A. Kenik

Keyword(s):

Copper Alloys ◽

Range Order ◽

Local Composition ◽

Chemical Order ◽

Cu Alloys ◽

Ti Alloys ◽

Void Swelling ◽

Aluminum Copper Alloys ◽

Modulated Structures ◽

The Stability

Short-range order (SRO) or clustering strongly influences swelling in alloys. For example, Al-Cu alloys containing G-P zones, Cu-Ti alloys containing modulated structures, and Ni-Mo alloys containing various degrees of chemical order are all resistant to void swelling caused by displacive irradiation at elevated temperature. Conversely, displacive particle irradiations may change the configuration of local composition variations. When aluminum-copper alloys containing G-P zones are irradiated with 1 MeV electrons a transformation to 'θ' occurs, and the usually observed θ” state is not observed. This paper presents the results of an experimental investigation of order stability in Ni—20 at. % Mo alloys during irradiation with 1 MeV electrons. This alloy is especially useful for studying the stability of order during irradiation because the symmetry of the intensity distribution in reciprocal space corresponding to SRO is quite different from that corresponding to the Dla long-range order (LRO) observed at thermal equilibrium in this alloy.

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Experimental Study on Evolution Process of Short Fatigue Crack in 2A12 Alloy under Complex Stress State

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.703.202 ◽

2016 ◽

Vol 703 ◽

pp. 202-206

Author(s):

Shan Lin Liu ◽

Lu Wang ◽

Zheng Wang

Keyword(s):

Aluminum Alloy ◽

Fatigue Crack ◽

Fatigue Life ◽

Phase Particle ◽

Fatigue Behavior ◽

Crack Coalescence ◽

Experimental Result ◽

Second Phase ◽

Middle Stage ◽

Short Fatigue Crack

The fatigue behavior of 2A12 Aluminum alloy was experimentally studied through different annular notched specimens under symmetrical triangle with the frequency of 0.5 Hz. The experimental result showed that the microstructure played an important role during the entire fatigue life of 2A12 Aluminum alloy. The short fatigue crack only initiated due largely to the second-phase particle such as the S phase (Al2CuMg), the θ phase (CuAl2) and especially the black impurity phases debonding from the basal body when the fatigue cycle was sufficient. The cracks propagated separately along the circumferential direction of the notch, crack coalescence and interaction of cracks were not common at early and middle stage of short crack’s fatigue life. Cracks tended to propagate along direction different from the original one after crack coalescence. Surface crack length at early and middle stage of short crack’s fatigue life were presented. These curves showed crack growth rate increased relatively as the reducing of notched radius or the increasing of nominal strain amplitude which implied that geometry and loading conditions were the factors of the crack propagation.

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