scholarly journals Influence of Minor Zn Addition on Precipitation Behavior and Intergranular Corrosion Properties of Al-Mg-Si Alloy

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 650 ◽  
Author(s):  
Shuiqing Chi ◽  
Yunlai Deng ◽  
Xuehong Xu ◽  
Xiaobin Guo
Keyword(s):  
Electron Microscope ◽  
Intergranular Corrosion ◽  
Corrosion Current ◽  
Age Hardening ◽  
Peak Hardness ◽  
Precipitation Behavior ◽  
Corrosion Properties ◽  
Free Zone ◽  
Transmission Electron ◽  
Zn Addition

The effect of 0.2 wt.% Zn addition on microstructure, age hardening and intergranular corrosion (IGC) properties of Al-Mg-Si alloy were investigated by scanning electron microscope, transmission electron microscope, hardness testing, and electrochemistry testing. The results showed that the addition of Zn can accelerate the transformation of GP zones into β″, and make the intragranular precipitates become smaller and with higher density. This is beneficial to the precipitation strengthening of the alloy, leading to obtaining higher hardness and enhancing the age hardening response. The peak hardness of the alloy with the addition of Zn is 125.8 HV which means increasing the hardness by 12.7 HV, compared with the alloy without Zn. However, the addition of Zn makes the precipitate-free zone (PFZ) of the alloy wider, and coarsens the grain boundary precipitates slightly, which result in the reduction of IGC resistance of Al-Mg-Si alloy. The maximum corrosion depth of the Zn-containing alloy is 121.3 μm in the peak age condition, which is 35.7 μm deeper than the alloy without Zn. The result of the potentiodynamic polarization curves also demonstrated the increase of IGC sensitivity. The corrosion current density of the alloy with added Zn is 0.595 μA/cm2 in the peak age condition, while that for the alloy without Zn is 0.199 μA/cm2.

Precipitation in Al-Li-Cu Alloys

1981 ◽  
Vol 39 ◽  
pp. 44-45
Author(s):  
J. E. O'Neal ◽  
K. K. Sankaran
Keyword(s):  
Electron Microscopy ◽  
Age Hardening ◽  
Precipitation Behavior ◽  
Zone Formation ◽  
Specific Strength ◽  
Hardening Behavior ◽  
Cu Alloys ◽  
High Specific Strength ◽  
Transmission Electron ◽  
Structural Applications

Al-Li-Cu alloys combine high specific strength and high specific modulus and are potential candidates for aircraft structural applications. As part of an effort to optimize Al-Li-Cu alloys for specific applications, precipitation in these alloys was studied for a range of compositions, and the mechanical behavior was correlated with the microstructures.Alloys with nominal compositions of Al-4Cu-2Li-0.2Zr, Al-2.5Cu-2.5Li-0.2Zr, and Al-l.5Cu-2.5Li-0.5Mn were argon-atomized into powder at solidification rates ≈ 103°C/s. Powders were consolidated into bar stock by vacuum pressing and extruding at 400°C. Alloy specimens were solution annealed at 530°C and aged at temperatures up to 250°C, and the resultant precipitation was studied by transmission electron microscopy (TEM).The low-temperature (≲100°C) precipitation behavior of the Al-4Cu-2Li-0.2Zr alloy is a combination of the separate precipitation behaviors of Al-Cu and Al-Li alloys. The age-hardening behavior at these temperatures is characteristic of Guinier-Preston (GP) zone formation, with additional strengthening resulting from the coherent precipitation of δ’ (Al3Li, Ll2 structure), the presence of which is revealed by the selected-area diffraction pattern (SADP) shown in Figure la.

Evolution of Nanostructure during the Early Stages of Ageing in Al-Zn-Mg-Cu Alloys

2006 ◽  
Vol 519-521 ◽  
pp. 555-560 ◽  
Author(s):  
Peter V. Liddicoat ◽  
Tomoyuki Honma ◽  
L.T. Stephenson ◽  
Simon P. Ringer
Keyword(s):  
Atom Probe Tomography ◽  
Atom Probe ◽  
Age Hardening ◽  
Peak Hardness ◽  
Cu Alloys ◽  
Transmission Electron ◽  
Element Species ◽  
Hardness Increase ◽  
Solute Interactions ◽  
Effect Of Copper

During age-hardening of certain Al-Zn-Mg-Cu alloys, a 90% hardness increase can occur with 75 seconds. The clustering and precipitation of solute element species during this early rapid hardening (RH) period has been investigated through atom probe tomography, transmission electron microscopy, and Vickers hardness measurements. This study has focussed on the effect of copper by analysing three alloys; Al-2.0Zn-1.8Mg-0.7Cu, Al-2.0Zn-1.7Mg-0.2Cu and Al-1.9Zn-1.7Mg (at.%). The early RH reaction in these alloys accounts for up to 70% of the total hardening (peak hardness minus as-quenched hardness) and takes place during the first 60 seconds of ageing. We report preferred solute-solute interactions in the as-quenched materials. This quenched-in nanostructure acts as a template for subsequent solute clustering, the nature of which we have correlated with ageing.

Microstructure Imaging, Precipitation Formation and Mechanical Properties: Al–Li and Al–Mg–Zn Alloys

2019 ◽  
Author(s):  
Wilfried Wunderlich ◽  
Janos Lendvai ◽  
Hans-Joachim Gudladt
Keyword(s):  
Hydrogen Embrittlement ◽  
Driving Force ◽  
Hydrogen Diffusion ◽  
Nano Particles ◽  
Peak Hardness ◽  
Free Zone ◽  
The Third ◽  
Transmission Electron ◽  
Moisture Conditions ◽  
Precipitation Formation

This article describes concepts of three features of microstructure–properties relationship, first the imaging and formation of nano-particles, then their contribution to hardness, and finally hydrogen embrittlement during fatigue. First, we briefly review the imaging modes in transmission electron microscopy (TEM) for nano-sized precipitates. The next issue is the hardening in Aluminum alloys, which is caused by GP-zones or precipitates, formed at the second step of the annealing process. After homogenization, the peak-hardness can be generally achieved by a few hours of annealing between 120°C and 200°C. Hardness measurements and equal-channel axial pressing (ECAP) showed that even at room temperature the driving force for formation of the particles is so strong that already within one hour of annealing after homogenization a remarkable hardening occurs. The third issue, hydrogen embrittlement, is caused by oxidation of pure Al surfaces produced at the crack tip during fatigue under ambient or wet moisture conditions. The cracks propagate preferentially along the precipitation free zone adjacent to grain boundaries, where hydrogen diffusion is fastest.

Effect of Mg/Si Ratio on Hardening Behavior, Microstructure and Properties of Al-Mg-Si Alloys

2022 ◽  
Vol 905 ◽  
pp. 56-60
Author(s):  
Ya Ya Zheng ◽  
Tao Long ◽  
Bing Li
Keyword(s):  
Mechanical Properties ◽  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Intergranular Corrosion ◽  
Corrosion Test ◽  
Electrochemical Test ◽  
Microstructure And Properties ◽  
Hardening Behavior ◽  
Transmission Electron ◽  
Precipitation Behaviour

The effects of Mg/Si ratio on precipitation behaviour and properties of Al-Mg-Si alloys were studied by using electrochemical test, corrosion test and transmission electron microscope (TEM). The results show that with the increases of Mg/Si ratio from 0.9 to 1.1, the density of the β" decreases, and the mechanical properties decrease. When the ratio of Mg/Si increases from 1.0 to 1.1, the density y of β" does not increase significantly, but the continuous degree of the MgSi phase decreases significantly. The source of cracks originate from MgSi phase, which reduces the mechanical properties. When the Mg/Si ratio is 0.9, the alloy is in an over-Si state, which results in serious intergranular corrosion (IGC).

HRTEM Observation of the Age Hardening Precipitates in Mg-Zn Alloy

2007 ◽  
Vol 26-28 ◽  
pp. 157-160
Author(s):  
Shogo Mori ◽  
Tokimasa Kawabata ◽  
Kenji Matsuda ◽  
Susumu Ikeno
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Early Stage ◽  
Age Hardening ◽  
Aged Specimen ◽  
Transmission Electron ◽  
Hrtem Observation ◽  
Peak Aged ◽  
Zn Alloy ◽  
Different Parts

The age hardening precipitates of Mg-4.7mass%Zn alloy aged at 423K,473K were studied by using high-resolution transmission electron microscope (HRTEM). Contrasts of mono layers were confirmed to exist on the (0001) and (1100) matrix planes. It was considered that the contrast of mono layer was plate-like shape, and identified as pre-precipitates from as-quenched stage to early stage of aging at 473K for 32h . In the peak aged specimen of aged at 473K, the β1’ phase was observed. The β1’ phase has a rod-like shape and parallel to c-axis of Mg matrix. It can be observed orientation relationship between Mg matrix and β1’phase has not only same parts to previous reports but also different parts in one β1’ phase .

TEM Study for Strengthening Mechanisms in Elgiloy

2010 ◽  
Vol 442 ◽  
pp. 268-274 ◽  
Author(s):  
I.N. Qureshi ◽  
S. Rani ◽  
F. Yasmin ◽  
M. Farooque
Keyword(s):  
Electron Microscope ◽  
Cold Work ◽  
Cold Deformation ◽  
Solution Treatment ◽  
Optical Microscope ◽  
Age Hardening ◽  
Solution Treated ◽  
Transmission Electron ◽  
P Transformation ◽  
Cold Worked

Elgiloy is Co based alloy (40wt%Co, 20wt%Cr, 15wt%Ni, 14wt%Fe and 7wt%Mo). It was strengthened by cold work and is capable of additional hardening by aging. The effects of solution treatment, cold working and age-hardening on the microstructure of elgiloy were investigated using optical microscope, scanning electron microscope (SEM) and transmission electron microscope (TEM). As rolled strips were solution treated at 1065°C/1hr. These solution treated strips were then reduced 50% by cold rolling. After cold-deformation both є-hcp phase and fcc deformation twins are also considered to coexist at room temperature. The cold worked strips were then age hardened at (450-600)°C. The age hardened strips showed formation of additional є-phase (via α f c c є h c p transformation).

Multiple Precipitation Behavior of Niobium Carbide and Copper in Martensitic Steel

2010 ◽  
Vol 89-91 ◽  
pp. 395-399 ◽  
Author(s):  
Masahiro Murakami ◽  
Nobuo Nakada ◽  
Toshihiro Tsuchiyama ◽  
Setsuo Takaki ◽  
Yoshitaka Adachi
Keyword(s):  
Niobium Carbide ◽  
Aging Treatment ◽  
Age Hardening ◽  
Peak Hardness ◽  
Precipitation Behavior ◽  
Tempered Martensite ◽  
5Mn Steel ◽  
Crystallographic Characteristics ◽  
Crystallographic Orientation Relationship ◽  
Martensite Matrix

The multiple precipitation behavior of NbC and Cu particles in martensitic structure was investigated by using 0.05C-0.46Nb-2Cu-1.5Mn steel (NbC-Cu steel). Additionally, 0.05C-0.45Nb-2Mn steel (NbC steel) and 2Cu-5Mn steel (Cu steel) were also prepared to examine the respective precipitation behaviors of NbC and Cu. Aging treatment at 873K after quenching revealed that these steels exhibit typical age hardening. Comparing the NbC steel and Cu steel in the precipitation rate, the Cu precipitated much faster than the NbC. On the other hand, the peak hardness in NbC-Cu steel is higher than that by the respective precipitations in NbC steel and Cu steel. Besides, the aging time for the peak hardness in NbC-Cu steel was between those in NbC steel and Cu steel. This suggests that the NbC and Cu particles were separately precipitated within martensite matrix and each of them contributed to the hardening in NbC-Cu steel. As a result of TEM investigation for crystallographic characteristics of the precipitates, the NbC and Cu particles had different crystallographic orientation relationship with tempered martensite matrix: Baker-Nutting relationship for NbC particle and Kurdjumov-Sachs relationship for Cu particle.

Improvement of Stress Corrosion Cracking (SCC) Resistance of a 7150 Al-Zn-Mg-Cu Alloy by Retrogression and Reageing (RRA) Treatment

2014 ◽  
Vol 984-985 ◽  
pp. 529-535 ◽  
Author(s):  
Prasanta Kumar Rout ◽  
M.M. Ghosh ◽  
K.S. Ghosh
Keyword(s):  
Electron Microscope ◽  
Grain Boundary ◽  
Transmission Electron Microscope ◽  
Stress Corrosion Cracking ◽  
Peak Hardness ◽  
Slow Strain Rate Test ◽  
Cu Alloy ◽  
Transmission Electron ◽  
Crack Morphology ◽  
Rate Test

A 7150 Al-Zn-Mg-Cu alloy is artificially aged at 120 oC for varying time. The peak hardness (T6 temper) is obtained at about 24 h at that temperature. Further, the T6 temper is subjected to retrogression and reageing (RRA) treatment. Slow strain rate test (SSRT) has been carried out on the T6 and RRA tempers. SSRT results indicated that the RRA temper have higher resistance to SCC compared to that of T6 temper. SCC behaviour of the alloy tempers have been explained with the help of microstructural features studied by transmission electron microscope (TEM). The large, discrete and discontinuous grain boundary precipitates observed in the microstructure of the RRA temper are believed to be the responsible factor for achieving higher SCC resistance. Further, SEM fractographs and crack morphology have also been analyzed to evaluate the SCC behaviour of the alloy tempers.

Microsture and Properties of a Cu-Cr-Zr-Fe-Ti Alloy

2015 ◽  
Vol 723 ◽  
pp. 556-560
Author(s):  
Fu Xiang Huang
Keyword(s):  
Electron Microscopy ◽  
Electrical Conductivity ◽  
Transmission Electron Microscopy ◽  
Age Hardening ◽  
Peak Hardness ◽  
Ti Alloy ◽  
Hardening Behavior ◽  
Transmission Electron ◽  
Zn Alloys ◽  
Scanning Electron

The effect of 0.45 wt. % Fe and 0.2 wt. % Ti additions on the age hardening behavior of Cu-Cr-Zr-Zn alloys has been investigated with respect to hardness, electrical conductivity and microstructure. It was showed that the addition of Fe /Ti to Cu-Cr-Zr-Zn alloys enhance strength and hardness, but decrease the electrical conductivity, and increase the aging temperature and time for attaining peak hardness. The scanning electron microscope (SEM) and transmission electron microscopy (TEM) results showed that there are four types of phases in the alloy, Cu-matrix, Cr-rich, (Cu,Zr)-rich and (Fe,Ti)-rich phases.

MICROSTRUCTURE EVOLUTION AND CORROSION PROPERTY OF MEDIUM-CARBON ALLOY STEEL AFTER HIGH-TEMPERATURE CARBURIZATION PROCESS

2016 ◽  
Vol 23 (05) ◽  
pp. 1650038
Author(s):  
DENG DEWEI ◽  
NIU TINGTING ◽  
LIU HAIYING ◽  
ZHANG LIN ◽  
SUN QI
Keyword(s):  
Electron Microscope ◽  
Electrochemical Corrosion ◽  
Corrosion Current ◽  
Optical Microscope ◽  
Corrosion Property ◽  
Carbon Steels ◽  
Smooth Transition ◽  
Hardness Profile ◽  
Medium Carbon ◽  
Transmission Electron

In the present study, the effects of carburization treatment on the microstructure and corrosion property of medium-carbon steels (40Cr) were investigated by means of X-ray diffraction (XRD), electron microprobe analyzer (EMPA), optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM) and electrochemical corrosion, respectively. It was found that the microstructures beneath the surface were refined and a smooth transition microstructure from the surface to the core was observed in carburized samples. The fine plate-like but not granular carbide precipitation (Cr7C3) was observed in carburized sample by heat-treatment. The carburized specimens exhibited some effectiveness in the improvement of hardness and a smooth transition hardness profile. Corrosion resistance of 40Cr was improved by carburization treatment, resulting in the higher self-corrosion potential and the lower self-corrosion current density.

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