Effects of alloying elements (Sn, Cr and Cu) on second phase particles in Zr-Sn-Nb-Fe-(Cr, Cu) alloys

Magnesium (Mg) alloys constitute an attractive structural material for transportation industries, due to their low density and high strength/weight ratio. However, high susceptibility to corrosion of Mg alloys limits their use. Therefore, there is a growing interest for development of new Mg alloys with good mechanical properties and superior corrosion resistance. Production of wrought Mg alloys results in enhancement of mechanical properties, whereas addition of alloying elements may result in improved corrosion behavior. In this study we distinguish the role of aluminum, zinc, tin and calcium additions on the corrosion performance of new wrought Mg alloys. Overall, addition of alloying elements resulted in precipitation of second phase particles with cathodic behavior (relatively to Mg matrix). This enhanced the micro-galvanic effects and the corrosion resistance in short periods of immersion was deteriorated. However, in longer periods of immersion the passive characteristics of the oxide layer played a significant role in improving the alloys' corrosion resistance. The contribution of each element to the oxide layer will be discussed in detail. In general, the quantities of alloying element should be sufficient to stabilize the corrosion products layer; yet as low as possible, in order to reduce the micro-galvanic effects.

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Effects of Excessive Zr Content and Ultrasonic Treatment on Microstructure and Mechanical Properties of Al-Zn-Mg-Cu Alloy

Metals ◽

10.3390/met11040632 ◽

2021 ◽

Vol 11 (4) ◽

pp. 632

Author(s):

Cheng Li ◽

Shusen Wu ◽

Shulin Lü ◽

Jianyu Li ◽

Longfei Liu ◽

...

Keyword(s):

Mechanical Properties ◽

Grain Size ◽

Ultrasonic Vibration ◽

Ultrasonic Treatment ◽

Second Phase ◽

Cu Alloy ◽

Cu Alloys ◽

Microstructure And Mechanical Properties ◽

Second Phase Particles ◽

Properties Of Materials

The Zr element is one of the important grain refiners for 7xxx series Al-Zn-Mg-Cu alloys, but the effect of Zr content more than 0.15 wt.% needs to be deeply investigated under the action of ultrasonic vibration. In this study, the effects of Zr contents (0.1 to 0.25 wt.%) on microstructure and mechanical properties of Al-Zn-Mg-Cu alloy were studied. The results showed that Zr element could refine grains, but when the Zr content was greater than 0.15 wt.%, the grain size was not uniform, the number of second phase particles increased, and the segregation of components became more serious. It was found that after ultrasonic treatment, the grain-size inhomogeneity was greatly improved, and the Zr content could be added up to 0.2 wt.%. When the Zr content is equal or lower than 0.2 wt.%, ultrasonic treatment can effectively improve the mechanical properties of materials by refining grains and weakening segregation. However, when the Zr content is up to 0.25 wt.%, the effect is getting worse.

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Non-Heat Treatable Al-Alloys: Development of Intermetallic Particles during Solidification and Homogenization

Encyclopedia of Aluminum and Its Alloys ◽

10.1201/9781351045636-140000223 ◽

2019 ◽

Author(s):

Olaf Engler ◽

Katrin Kuhnke ◽

Jochen Hasenclever

Keyword(s):

Mechanical Properties ◽

Solid Solution ◽

Electrical Conductivity ◽

Al Alloys ◽

Alloying Elements ◽

Second Phase ◽

Phase Selection ◽

Industrial Processing ◽

Intermetallic Particles ◽

Second Phase Particles

The materials properties of Al-alloys are controlled by the added alloying elements and by the processing conditions through the resulting materials microstructure. An important aspect in the description of the microstructure is the constitution of the material in terms of alloying elements in solid solution and, in turn, volume, size, morphology, and species of second-phase particles. These constitutional characteristics, conveniently summarized as microchemistry, have an impact on physical properties like thermal or electrical conductivity and on mechanical properties including strength and formability of Al-alloys. In the present article, we summarize the phase selection upon solidification and the changes in microchemistry during subsequent homogenization annealing during conventional industrial processing of non-heat-treatable Al wrought alloys.

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Polishing process effect on the image of dispersed precipitates

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100112646 ◽

1984 ◽

Vol 42 ◽

pp. 534-535

Author(s):

C.T. Hu ◽

C.W. Allen

Keyword(s):

Matrix Material ◽

Specimen Preparation ◽

Second Phase ◽

Precipitate Particle ◽

Polishing Process ◽

Second Phase Particles ◽

The Matrix ◽

Surface Profiles ◽

Thinning Process

One important problem in determination of precipitate particle size is the effect of preferential thinning during TEM specimen preparation. Figure 1a schematically represents the original polydispersed Ni3Al precipitates in the Ni rich matrix. The three possible type surface profiles of TEM specimens, which result after electrolytic thinning process are illustrated in Figure 1b. c. & d. These various surface profiles could be produced by using different polishing electrolytes and conditions (i.e. temperature and electric current). The matrix-preferential-etching process causes the matrix material to be attacked much more rapidly than the second phase particles. Figure 1b indicated the result. The nonpreferential and precipitate-preferential-etching results are shown in Figures 1c and 1d respectively.

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Analytical Electron Microscopy Study of Second-Phase Particles in 7075 and 7475 Aluminum Alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100118618 ◽

1985 ◽

Vol 43 ◽

pp. 348-349

Author(s):

M. Raghavan ◽

J. Y. Koo ◽

J. W. Steeds ◽

B. K. Park

Keyword(s):

Aluminum Alloys ◽

Silicon Oxide ◽

Analytical Electron Microscopy ◽

Microscopy Study ◽

Electron Microscopy Study ◽

Partial Substitution ◽

Second Phase ◽

X Ray ◽

Second Phase Particles ◽

Almost All

X-ray microanalysis and Convergent Beam Electron Diffraction (CBD) studies were conducted to characterize the second phase particles in two commercial aluminum alloys -- 7075 and 7475. The second phase particles studied were large (approximately 2-5μm) constituent phases and relatively fine ( ∼ 0.05-1μn) dispersoid particles, Figures 1A and B. Based on the crystal structure and chemical composition analyses, the constituent phases found in these alloys were identified to be Al7Cu2Fe, (Al,Cu)6(Fe,Cu), α-Al12Fe3Si, Mg2Si, amorphous silicon oxide and the modified 6Fe compounds, in decreasing order of abundance. The results of quantitative X-ray microanalysis of all the constituent phases are listed in Table I. The data show that, in almost all the phases, partial substitution of alloying elements occurred resulting in small deviations from the published stoichiometric compositions of the binary and ternary compounds.

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Development of Second-Phase Particles during Solidification and Homogenization of Aluminium Alloy AlMn1

Practical Metallography ◽

10.3139/147.110556 ◽

2019 ◽

Vol 56 (5) ◽

pp. 317-341 ◽

Cited By ~ 1

Author(s):

O. Engler ◽

K. Kuhnke ◽

K. Westphal

Keyword(s):

Aluminium Alloy ◽

Second Phase ◽

Second Phase Particles

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Evidence of hydrogen trapping at second phase particles in zirconium alloys

Scientific Reports ◽

10.1038/s41598-021-83859-w ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Christopher Jones ◽

Vidur Tuli ◽

Zaheen Shah ◽

Mhairi Gass ◽

Patrick A. Burr ◽

...

Keyword(s):

Density Functional ◽

Secondary Ion Mass Spectrometry ◽

Zirconium Alloys ◽

Nuclear Industry ◽

Second Phase ◽

Hydrogen Trapping ◽

Functional Theory ◽

Second Phase Particles ◽

Hydrogen Isotope Ratios ◽

Dft Modelling

AbstractZirconium alloys are used in safety–critical roles in the nuclear industry and their degradation due to ingress of hydrogen in service is a concern. In this work experimental evidence, supported by density functional theory modelling, shows that the α-Zr matrix surrounding second phase particles acts as a trapping site for hydrogen, which has not been previously reported in zirconium. This is unaccounted for in current models of hydrogen behaviour in Zr alloys and as such could impact development of these models. Zircaloy-2 and Zircaloy-4 samples were corroded at 350 °C in simulated pressurised water reactor coolant before being isotopically spiked with 2H2O in a second autoclave step. The distribution of 2H, Fe and Cr was characterised using nanoscale secondary ion mass spectrometry (NanoSIMS) and high-resolution energy dispersive X-ray spectroscopy. 2H− was found to be concentrated around second phase particles in the α-Zr lattice with peak hydrogen isotope ratios of 2H/1H = 0.018–0.082. DFT modelling confirms that the hydrogen thermodynamically favours sitting in the surrounding zirconium matrix rather than within the second phase particles. Knowledge of this trapping mechanism will inform the development of current understanding of zirconium alloy degradation through-life.

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