Effect of Second Phase Particles on the Tensile Instability of a Nanostructured Al-1%Si Alloy

2014 ◽  
Vol 783-786 ◽  
pp. 2629-2634 ◽  
Author(s):  
Tian Lin Huang ◽  
Gui Lin Wu ◽  
Qing Liu ◽  
Xiao Xu Huang
Keyword(s):  
Tensile Tests ◽  
Structural Features ◽  
Second Phase ◽  
Commercial Purity ◽  
Localized Deformation ◽  
Dispersed Particles ◽  
Transmission Electron ◽  
Second Phase Particles ◽  
Tensile Instability ◽  
Recovery Annealing

A nanostructured Al-1%Si alloy containing dispersed Si particles was produced by heavily cold-rolling to study the effect of second phase particles on the tensile instability of nanostructured metals. Tensile tests were conducted on the as-deformed sample and the samples after recovery annealing treatments. The structural features of deformed and annealed samples were characterized by transmission electron microscopy. By comparing with the behavior of nanostructured commercial purity Al without dispersed particles, a remarked improvement in the tensile stability was found. This is related to a prevention of localized deformation by the presence of finely dispersed Si particles in the nanoscale matrix structure.

scholarly journals AA2219 Aluminum Alloy Processed via Multi-Axial Forging in Cryogenic and Ambient Environments

2019 ◽  
Vol 8 (2) ◽  
pp. 1 ◽  
Author(s):  
Amin Azimi ◽  
Gbadebo Moses Owolabi ◽  
Hamid Fallahdoost ◽  
Nikhil Kumar ◽  
Horace Whitworth ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Room Temperature ◽  
Tensile Tests ◽  
Second Phase ◽  
X Ray Diffraction ◽  
Transmission Electron Microscopy Micrographs ◽  
Transmission Electron ◽  
Second Phase Particles ◽  
Aa2219 Aluminum Alloy ◽  
Cryogenic Processing

This paper presents the microstructure and the mechanical behavior of nanocrystalline AA2219 processed by multi axial forging (MAF) at ambient and cryogenic temperatures. The X-ray diffraction pattern and transmission electron microscopy micrographs in the initial microstructure characterization indicate a more effective severe plastic deformation during the cryogenic MAF than the same process conducted at room temperature. MAF at cryogenic temperature results in crystallite size reduction to nanoscales as well as second phase particles breakage to finer particles which are the crucial factors to increasing the mechanical properties of the material. Fractography analysis and tensile tests results show that cryogenic forging does not only increase the mechanical strength and toughness of the alloys significantly, but also improves the ductility of the material in comparison with the conventional forging. In this comparative regard, cryogenic processing provides 44% increase in the tensile strength of the material only after 2 forging cycles when compared to the room temperature process. In addition, further forging process to the next cycles slightly enhances the tensile strength at the expense of ductility due to less ability of the dislocations to accumulate. However, the ductility of the ambient temperature forged samples decreases at a faster rate than that of cryoforged samples.

Transmission electron microscopy observation of second-phase particles in β–Si3N4 grains

1999 ◽  
Vol 14 (7) ◽  
pp. 2959-2965 ◽  
Author(s):  
Naoto Hirosaki ◽  
Tomohiro Saito ◽  
Fumio Munakata ◽  
Yoshio Akimune ◽  
Yuichi Ikuhara
Keyword(s):  
Electron Microscopy ◽  
Silicon Nitride ◽  
Heat Treating ◽  
High Resolution Electron Microscopy ◽  
Second Phase ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Second Phase Particles ◽  
Coarse Grains ◽  
Sintered Silicon

Silicon nitride was fabricated by adding Y2O3 and Nd2O3 as sintering additives, sintering for 8 h at 1900 °C, and heat treating for 4 h at 2200 °C to enhance grain growth. The microstructure was investigated by scanning electron microscopy, high-resolution electron microscopy, energy dispersive x-ray spectroscopy (EDS), and electron microdiffraction. This material had a duplex microstructure composed of many fine grains and a few coarse grains. In β–Si3N4 grains, second-phase particles with the composition of liquid phase, Y–Nd–Si–O or Y–Nd–Si–O–N, in the size of 10–30 nm were observed. EDS spectra and microdiffraction patterns revealed that those were amorphous or crystalline particles of Y–Nd–apatite, (Y,Nd)10Si6O24N2. These particles were presumably formed during cooling by the precipitation of Y–Nd–Si–O–N, which was trapped in the β–Si3N4 grains as solid solution or trapped liquid. The results suggest that attention should be paid to the trace amounts of trapped elements in β–Si3N4 grains in trying to improve the thermal conductivity of sintered silicon nitride.

scholarly journals Effect of Niobium and Titanium Addition on Formation of Second Phase Particles in CHQ Steel Using Transmission Electron Microscope

2021 ◽  
Vol 40 (1) ◽  
pp. 31-37
Author(s):  
Shahid Hussain Abro
Keyword(s):  
Heat Treatment ◽  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Weight Percent ◽  
Holding Time ◽  
Second Phase ◽  
Steel Matrix ◽  
Ehlers Danlos Syndrome ◽  
Transmission Electron ◽  
Second Phase Particles

It is common practice that formation of second phase particles such as nitrides or carbides in the steel matrix has significant role to control the grain size of steel. An attempt is made in the present research work to find out the role of nitrogen to form the nitride particles either with Al, Ti, B, Cr or Si. Two steel samples Steel-A and Steel-B with same titanium and aluminum weight percent in the chemical composition were obtained in hot rolled conditions from international market with only the difference of presence of Niobium in Steel-A. Solution heat treatment was performed at 1350°C with 60 minutes holding time in protherm heat treatment furnace available locally was used to dissolve the particles and then steel samples were reheat treated at 800°C with holding time of 60 minutes and water quenched and microstructure was revealed. Transmission electron microscope connected with Ehlers-Danlos Syndrome (EDS) was used to reveal the morphology of second phase particles. Both samples for a high resolution power Transmission Electron Microscopy (TEM) (Jeol JEM 3010) analysis were prepared by using carbon extraction replica method in 5% Nital solution as an etching technique. Both samples were then caught in copper grid of 3mm for using TEM analysis. TEM micrographs clearly revealed the second phase particles in the matrix of steel. The EDS peaks were studied and it was found that the peaks showed the titanium peaks in both the samples A and B and surprisingly there was no any peak found for aluminum. Stoichiometric calculations were carried out and it was found that weight percent nitrogen required for forming TiN is 0.0073, however the total nitrogen present in both the steels A and B is 0.0058 and 0.0061 respectively. That means that all the nitrogen present in the steel matrix was consumed by titanium to form the Titanium Nitride (TiN) so there was no nitrogen remain to fulfil the requirement of aluminum to form the Aluminum Nitride (AlN) particles.

scholarly journals Unravelling the characteristics of Al-alloy corrosion at the atomic to nanometre scale by transmission electron microscopy

2020 ◽  
Vol 326 ◽  
pp. 01007
Author(s):  
Shravan K. Kairy ◽  
Nick Birbilis
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Al Alloy ◽  
Second Phase ◽  
Clear Understanding ◽  
Transmission Electron ◽  
Second Phase Particles ◽  
Al Matrix

The localised corrosion associated with Mg2Si in the Al-matrix of an Al-Mg-Si alloy was studied in 0.1 M NaCl at pH 6 by quasi in-situ transmission electron microscopy. Herein, physical imaging of corrosion at the atomic to nanometre scale was performed. Phase transformation and subsequent chemical composition variations associated with the localised corrosion of Mg2Si were studied. It was observed that corrosion initiated upon Mg2Si, often preferentially at the interface with the Al-matrix, and propagated until Mg2Si was completely dealloyed by Mg-dissolution, resulting in an amorphous SiO-rich phase remnant. The SiO-rich remnant became electrochemically inert and did not initiate corrosion in the Al-matrix. This study provides a clear understanding on the localised corrosion of Al-alloys associated with Mg2Si. In addition, the methodology followed in this study can also be applied to understand the role of precipitates and second phase particles in the localised corrosion of Al-alloy systems.

scholarly journals Evolution of the Second-Phase Particles and Their Effect on Tensile Fracture Behavior of 2219 Al-xCu Alloys

Metals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 197
Author(s):  
Daofen Xu ◽  
Kanghua Chen ◽  
Yunqiang Chen ◽  
Songyi Chen
Keyword(s):  
Fracture Behavior ◽  
Solution Treatment ◽  
Aging Treatment ◽  
Fracture Initiation ◽  
Tensile Tests ◽  
Tensile Fracture ◽  
Second Phase ◽  
Cu Content ◽  
Second Phase Particles ◽  
Microcrack Propagation

In this study, the continuous evolution of the second-phase particles across as-cast, homogenization, multi-directional forging (MDF), and solution-aging treatment and their effect on tensile fracture behavior of 2219 aluminum alloys with different Cu contents was examined by optical microscopy (OM), scanning electron microscopy (SEM), and tensile tests. The results showed that the microstructure of as-cast 2219 aluminum alloy consisted of the α-Al matrix, Al2Cu coarse phase, and Fe-rich impurity phase. Severe segregation of Cu existed, and eutectic networks can be observed in the ingot. With an increase in Cu content, the eutectic networks became coarsen and thicker. During the complex improved process, the refinement mechanisms were fragmentation, dissolution, and diffusion of Al2Cu particles. Most fine Al2Cu particles were fully dissolved into the matrix and partial coarse particles were still retained after solution-aging treatment. Thus, the elongations of all the samples, undergoing solution treatment followed by water quenching, increased evidently. Then, the elongations decreased slightly due to the increase of precipitates. The fractography analysis of peak aged condition samples indicated that the fracture mode was diverted from a typical inter-granular fracture to a mainly trans-granular fracture with increase in Cu content from 5.56% to 6.52%. Fracture initiation mainly occurred by original microcrack propagation and microvoid nucleation at the coarse constituents.

Microstructure of Nb BASED A12O3 Composites

1998 ◽  
Vol 4 (S2) ◽  
pp. 588-589
Author(s):  
C. Scheu ◽  
G. Dehm ◽  
W. D. Kaplan ◽  
D. E. Garcia ◽  
N. Claussen
Keyword(s):  
Ceramic Composites ◽  
Second Phase ◽  
Pressureless Sintering ◽  
Powder Mixtures ◽  
Transmission Electron ◽  
Second Phase Particles ◽  
Wide Range ◽  
Metal Ceramic ◽  
High Resolution Tem ◽  
Al Powder

Metal-ceramic composites possess a wide range of applications due to an increased fracture toughness and strength compared to monolithic materials. A better understanding of the correlation between properties and microstructure of these materials requires a detailed analysis of the phases which form during processing. This can be accomplished by using various transmission electron microscopy (TEM) methods. In this study Nb based AI2O3 composites were investigated. The composites were prepared by pressureless sintering 2 of compacts of attrition milled AI2O3 and prealloyed Nb(Al) powder mixtures. The addition of 7 wt.% of Al to the Nb powder is supposed to assist in rapid and complete sintering of the material. The microstructure was studied in detail by conventional TEM using selected area diffraction (SAD). The chemistry and structure of the occurring phases, second phase particles and grain boundaries were analysed by analytical TEM and high resolution TEM (HRTEM).

Effect of Second-Phase Particles on Grain Refinement of Mg-Al-Zn Alloy during ECAE

2007 ◽  
Vol 546-549 ◽  
pp. 315-318
Author(s):  
Li Jin ◽  
Dong Liang Lin ◽  
Xiao Qin Zeng ◽  
Da Li Mao ◽  
Wen Jiang Ding
Keyword(s):  
Electron Microscopy ◽  
Grain Refinement ◽  
Equal Channel Angular Extrusion ◽  
Second Phase ◽  
Transmission Electron ◽  
Initial Stage ◽  
Mg17al12 Phase ◽  
Second Phase Particles ◽  
Zn Alloy ◽  
Zn Alloys

The effect of second-phase particles on the grain refinement of AZ61 and AZ91 Mg-Al-Zn alloys with different volume fractions of β-Mg17Al12 phase particles during equal channel angular extrusion (ECAE) has been investigated. The microstructure were observed by optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), which revealed that grain refinement was enhanced by second phase particles at initial stage of ECAE. And finer grains with the high angle grain boundaries (HAGBs) and disperse second-phase particles could be obtained in AZ61 and AZ91 after 8 passes of ECAE.

The effect of minor element concentrations on the strain rate sensitivity and ductility of commercial purity aluminium sheet

1980 ◽  
Vol 295 (1413) ◽  
pp. 130-130
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Minor Element ◽  
Tensile Tests ◽  
Plastic Instability ◽  
Alloy Sheet ◽  
Second Phase ◽  
Commercial Purity ◽  
Aluminium Sheet

Minor element levels vary considerably in commercial purity ( ca .99.5 % Al) aluminium alloy sheet obtained from various sources. Minor elements may be present in solution or as second phase particles formed during solidification or subsequent processing. The present work is largely concerned with the effects of elements in solution on strain-rate sensitivity and ductility. Recent treatments of plastic instability in tensile tests incorporate the strain rate sensitivity and note its importance in determining the strain at which instability occurs (Ghosh 1977; Marciniak 1974). Tensile properties have been determined on a range of aluminium sheet samples. The results show that small increases in solute concentration can result in a change from positive (flow stress increasing with strain rate) to negative strain rate sensitivity. The rate sensitivity was found to be strain dependent and this had led to a reconsideration of the effect of strain rate sensitivity on ductility. The work suggests that it is not the absolute value of the rate sensitivity that determines its effect on the strain to plastic instability, but rather the sign of its variation with strain. If this is positive then the strain to instability exceeds that expected in the absence of rate sensitivity; if the slope is negative the opposite trend is observed.

Study on the Preparation and Micro Structure of the Mg Containing Porous HA with Ultra-Fine Grain

2009 ◽  
Vol 610-613 ◽  
pp. 1132-1136
Author(s):  
Xing Yi Li ◽  
Xiang Cai Meng ◽  
Guo Quan Liu ◽  
Shi Dan Yuan
Keyword(s):  
Electron Microscopy ◽  
Photoelectron Spectroscopy ◽  
Chemical Precipitation ◽  
Second Phase ◽  
X Ray Diffraction ◽  
Micro Structure ◽  
X Ray ◽  
Fine Grain ◽  
Transmission Electron ◽  
Second Phase Particles

The Nano-HA powder were synthesized by chemical precipitation with Ca(H2PO4)2•H2O and Ca (OH)2 and porous HA was prepared by sintering with magnesium as pore-creator. Nano-HA powder and porous HA were characterized by wide angle X-ray diffraction, transmission electron microscopy(TEM), scanning electron microscopy (SEM), SEM in combination with energy dispersive X-ray spectroscopy (SEM-EDX), X-ray photoelectron spectroscopy. The experimental results show that HA powder synthesized by chemical precipitation is nanometer powder. Magnesium was ideal pore-creator for preparation of porous materials. The grain size of porous HA was sub-micron and MgO which existed in the grain boundary of HA as a second phase particles that played the roles of inhibiting the HA grain growth.

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