scholarly journals Rare Earth Metal-Based Intermetallics Formation in Al–Cu–Mg and Al–Si–Cu–Mg Alloys: A Metallographic Study

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
A. M. Samuel ◽  
E. M. Elgallad ◽  
M. G. Mahmoud ◽  
H. W. Doty ◽  
S. Valtierra ◽  
...  
Keyword(s):  
Eutectic Reaction ◽  
Earth Metal ◽  
Nucleation Site ◽  
Mg Alloys ◽  
Significant Drop ◽  
Metallographic Examination ◽  
Gray Phase ◽  
White Phase ◽  
Eutectic Si ◽  
Fixed Composition

This study was conducted on Al–Cu–Mg and Al–Si–Cu–Mg alloys containing either 5%La or 5%Ce. Two levels of Ti addition were examined, i.e., 0.05% and 0.15%. Thermal analysis was the only technique used to obtain castings, from which samples were then sectioned for metallographic examination. Based on the results obtained, the following points may be highlighted. Addition of a fairly large amount of RE metals (La or Ce) leads to the appearance of several peaks in the solidification curve between the precipitation of the primary α-Al phase and the (Al–Al2Cu) eutectic reaction. Although a significant drop in the eutectic temperature is caused by the addition of 5%La or Ce, the corresponding modification of the eutectic Si is marginal. Two main types of intermetallics were documented: a gray phase in the form of sludge with a fixed composition and a white phase in the shape of thin platelets. Due to the high affinity of RE to react with Si, Fe, and Cu, several compositions were obtained explaining the observed multiple peaks in the solidification curve. Judging by the morphology of the gray phase, it is assumed that this phase is precipitated in the liquid state and acts as a nucleation site for the white phase. Lanthanum and Ce can substitute each other.

scholarly journals Achievement of High Strength and Ductility in Al–Si–Cu–Mg Alloys by Intermediate Phase Optimization in As-Cast and Heat Treatment Conditions

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 647 ◽  
Author(s):  
Bingrong Zhang ◽  
Lingkun Zhang ◽  
Zhiming Wang ◽  
Anjiang Gao
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Intermediate Phase ◽  
High Strength ◽  
Mg Alloys ◽  
Artificial Ageing ◽  
Treatment Conditions ◽  
Eutectic Si

In order to obtain high-strength and high-ductility Al–Si–Cu–Mg alloys, the present research is focused on optimizing the composition of soluble phases, the structure and morphology of insoluble phases, and artificial ageing processes. The results show that the best matches, 0.4 wt% Mg and 1.2 wt% Cu in the Al–9Si alloy, avoided the toxic effect of the blocky Al2Cu on the mechanical properties of the alloy. The addition of 0.6 wt% Zn modified the morphology of eutectic Si from coarse particles to fine fibrous particles and the texture of Fe-rich phases from acicular β-Fe to blocky π-Fe in the Al–9Si–1.2Cu–0.4Mg-based alloy. With the optimization of the heat treatment parameters, the spherical eutectic Si and the fully fused β-Fe dramatically improved the ultimate tensile strength and elongation to fracture. Compared with the Al–9Si–1.2Cu–0.4Mg-based alloy, the 0.6 wt% Zn modified alloy not only increased the ultimate tensile strength and elongation to fracture of peak ageing but also reduced the time of peak ageing. The following improved combination of higher tensile strength and higher elongation was achieved for 0.6 wt% Zn modified alloy by double-stage ageing: 100 °C × 3 h + 180 °C × 7 h, with mechanical properties of ultimate tensile strength (UTS) of ~371 MPa, yield strength (YS) of ~291 MPa, and elongation to fracture (E%) of ~5.6%.

Role of Bi and Ca Additions in Controlling the Microstructure of Sr-Modified 319 Alloys

2006 ◽  
Vol 519-521 ◽  
pp. 1257-1264 ◽  
Author(s):  
S. El Hadad ◽  
A.M. Samuel ◽  
F.H. Samuel ◽  
H.W. Doty ◽  
S. Valtierra
Keyword(s):  
Electron Microscopy ◽  
Particle Size ◽  
Image Analysis ◽  
Mg Alloys ◽  
Microstructural Characteristics ◽  
Optical And Electron Microscopy ◽  
Modification Effect ◽  
Eutectic Si ◽  
Mg Addition

The role of bismuth (50 to 9000 ppm) and calcium (50 to 200 ppm) additions on the microstructural characteristics in Sr-modified 319 alloys (with/without 0.4 wt% Mg addition) were investigated using optical and electron microscopy, and image analysis. It was found that the modification effect of Sr continuously diminished with Bi addition up to ~3000 ppm Bi; further Bi addition led to the modification of the Si particles due to the presence of Bi. In the Ca-containing alloys, a coarse eutectic Si structure resulted with Ca additions of 50 ppm, due to the formation of Alx(Ca,Sr)Siy compounds. Increased Ca additions (up to 200 ppm) did not alter the Si particle size. The Alx(Ca,Sr)Siy phase particles appeared in rod-like form in the Sr-modified alloys and in plate-like form in the 319+0.4 wt% Mg alloys. MgO, Al2O3, and AlP particles appear to act as nucleants for the precipitation of the plate-like Alx(Ca,Sr)Siy phase.

scholarly journals Simultaneous Refinement of Primary Si and Modification of Eutectic Si in A390 Alloy Assisting by Sr-Modifier and Serpentine Pouring Channel Process

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3109 ◽  
Author(s):  
Pengyu Yan ◽  
Weimin Mao ◽  
Jing Fan ◽  
Bingkun Wang
Keyword(s):  
Eutectic Silicon ◽  
Primary Silicon ◽  
Interface Energy ◽  
Nucleation Site ◽  
Nucleation And Growth ◽  
Dominant Factor ◽  
Channel Process ◽  
Primary Si ◽  
Eutectic Si ◽  
A390 Alloy

In this study, A390 alloy was prepared using the combined process of a water-cooled copper serpentine pouring channel (SPC) and strontium (Sr) modifier, in order to simultaneously refine primary silicon (Si) and modify eutectic silicon (Si). The nucleation and growth mechanisms of the Si phase were discussed by morphology analysis and non-isothermal analytical kinetics. The results indicate that the size of primary Si is refined to 25.2–28.5 µm and the morphology of eutectic Si is modified from acicular into fibrous. The serpentine pouring channel process stimulates primary Si nucleation due to chilling effect and has no influence on eutectic Si nucleation. Impacts of Sr-modifier on primary and eutectic Si are similar, including three aspects: (1) poisoning of the nucleation site; (2) decreasing the interface energy between Si phase and liquid; (3) raising the activation energy for diffusion across solid-liquid interface. The content of Sr determines which one of the three aspects mentioned above is the dominant factor to promote or restrain the nucleation and growth of the primary and eutectic Si in hypereutectic Al-Si alloy.

scholarly journals Influence of the Solution and Artificial Aging Treatments on the Microstructure and Mechanical Properties of Die-Cast Al–Si–Mg Alloys

Metals ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 71
Author(s):  
Ho-Jung Kang ◽  
Jin-Young Park ◽  
Yoon-Suk Choi ◽  
Dae-Hyun Cho
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Solid Solution ◽  
Artificial Aging ◽  
Solution Treatment ◽  
Mg Alloys ◽  
Needle Type ◽  
Heat Treated ◽  
Die Cast ◽  
Eutectic Si

Heat treatment is widely used to improve the properties of Al–Si–Mg alloys and its outcomes are influenced by the parameters applied during the treatment. This study describes the effect of the solution and artificial aging treatments on the microstructure and mechanical properties of die-cast Al–Si–Mg alloys. The microstructure of the as-cast Al–Si–Mg alloy was mainly composed of α-Al, complex needle-type eutectic Si particles, Mg2Si, and α-AlFeMn. The complex needle-type eutectic Si particles disintegrated into spheroidal morphologies, while the Mg2Si was dissolved due to the solid solution treatment. The maximum yield strength (YS) and ultimate tensile strength (UTS) values were 126.06 and 245.90 MPa at 520 °C after 90 min of solution heat treatment, respectively. Although the YS and UTS values of the Al–Si–Mg alloys reduced due to the solution treatment, the elongation (EL) of the solid solution heat-treated Al–Si–Mg alloys was improved in comparison to that of the as-cast Al–Si–Mg alloy. The maximum YS and UTS of 239.50 and 290.93 MPa were obtained after performing artificial aging at 180 °C for 180 min, respectively. However, the EL of the aging heat-treated alloy was reduced by a minimal value.

Production and Metallographic Examination of Precipitable Cu–Mg Alloys

2011 ◽  
Vol 48 (11) ◽  
pp. 582-593 ◽  
Author(s):  
A. Zilly ◽  
U. Christian ◽  
S. Kött ◽  
D. Nobiling ◽  
N. Jost
Keyword(s):  
Mg Alloys ◽  
Metallographic Examination

Effect of Hot Rolling on the Microstructure and Mechanical Properties of Ti3Al Based Dual Phase Alloys

1998 ◽  
Vol 552 ◽  
Author(s):  
Jiansheng Wu ◽  
Lanting Zhang ◽  
Wei Hua ◽  
Guohua Qiu
Keyword(s):  
Hot Rolling ◽  
Room Temperature ◽  
Eutectic Reaction ◽  
Dual Phase ◽  
Cast State ◽  
Small Particles ◽  
Metallographic Examination ◽  
The Matrix ◽  
Effect Of Hot Rolling ◽  
Hot Rolled

ABSTRACTDevelopment of α 2-Ti3A1 based dual phase alloys have shown some promising potentials in property improvement by introducing Ti5Si3 sulicide phase into the matrix via Si alloying. However, the presence of coarse network of Ti5Si3phase formed by eutectic reaction in the as-cast state also embrittles the alloy. Both hot rolling and powder metallurgy are considered to be the possible ways to refine the Ti5Si3 phase in the matrix. Two Ti-Al-Si-Nb alloys whose Si contents are 2 and 5 at. % respectively were arc melted into ingots and then hot rolled to sheets in this investigation. Optical metallographic examination correlates the microstructures of the as-cast and as-rolled alloys with the different rolling amounts, showing that the coarse silicide network is broken into small particles after hot rolling. Mechanical property testing from room temperature to 8000°C indicates that the strength and plastic elongation of the hot-rolled alloys are much higher than those of the as-cast ones. The data obtained in this investigation are comparable with those obtained in the P/M processed specimens. Fracture surfaces of the alloys are also examined.

Accelerating pore nucleation and eutectic Si growth kinetics by increasing Cu and Sc for Al-Si-Mg alloys: In-situ observation

2021 ◽  
Vol 869 ◽  
pp. 159173
Author(s):  
Mingshan Zhang ◽  
Keli Liu ◽  
Bing Wang ◽  
Tingting Liang ◽  
Jiaqiang Han ◽  
...  
Keyword(s):  
Growth Kinetics ◽  
Mg Alloys ◽  
In Situ Observation ◽  
Eutectic Si ◽  
Pore Nucleation

scholarly journals Spheroidization and Coarsening of Eutectic Si Particles in Al-Si-Based Alloys

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Mohamed Ibrahim ◽  
Mohamed Abdelaziz ◽  
Agnes Samuel ◽  
Herbert Doty ◽  
Fawzy Samuel
Keyword(s):  
Mg Alloys ◽  
Spherical Particles ◽  
Heat Treated ◽  
Eutectic Si ◽  
Cast Alloys ◽  
Si Content ◽  
Solutionizing Time

The present study was carried out on three Al-Si cast alloys viz., 319, 356, and 413 alloys, solidified at 8°C/s. Samples from 319 and 413 alloys were solution heat-treated at 510°C, whereas samples from 356 alloy were solutionized at 550°C, for up to 1200 h. The results reveal that complete spheroidization of eutectic Si particles in terms of achieving individual spherical particles cannot be achieved in most Al-Si-Cu-Mg alloys even after a solutionizing time of 1200 h which contradicts with the existing theory. Addition of Sr to Cu-free 356 alloy could lead to complete spheroidization after 1200 h at 550°C if the alloy was solidified at 8°C/s. Besides the dissolution theory of Ostwald, coarsening of Si particles can as well take place by impingement, fusion, and agglomeration. Increasing the Si content makes it difficult to achieve spheroidization, i.e., fragmentation and coarsening. Results obtained from observations of deeply etched samples (3D) contradict those obtained from polished samples (2D).

scholarly journals Effect of Rare Earth Metals, Sr, and Ti Addition on the Microstructural Characterization of A413.1 Alloy

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
M. G. Mahmoud ◽  
A. M. Samuel ◽  
H. W. Doty ◽  
S. Valtierra ◽  
F. H. Samuel
Keyword(s):  
Rare Earth ◽  
Eutectic Temperature ◽  
Rare Earth Metals ◽  
Microstructural Characterization ◽  
Second Phase ◽  
White Phase ◽  
Eutectic Si ◽  
Ti Addition ◽  
Grey Phase

The present work was performed on A413.1 alloy containing 0.2–1.5 wt% rare earth metals (lanthanum or cerium), 0.05–0.15% Ti, and 0–0.02 wt% Sr. These elements were either added individually or combined. Thermal analysis, image analysis, and electron probe microanalysis were the main techniques employed in the present study. The results show that the use of the depression in the eutectic temperature as a function of alloy modification cannot be applied in the case when the alloy is treated with rare earth metals. Increasing the concentration of RE increases the solidification zone especially in Sr-modified alloys leading to poor feeding ability. This observation is more prominent in the case of Ce addition. Depending upon the amount of added Ti, two RE based intermetallics can be formed: (i) a white phase, mainly platelet-like (approximately 2.5 μm thick), that is rich in RE, Si, Cu, and Al and (ii) a second phase made up of mainly grey sludge particles (star-like) branching in different directions. The grey phase is rich in Ti with some RE (almost 20% of that in the white phase) with traces of Si and Cu. There is a strong interaction between RE and Sr leading to a reduction in the efficiency of Sr as a eutectic Si modifier causing particle demodification.

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