scholarly journals Determination of Al-2.18Mg-1.92Li Alloy’s Microstructure Degradation in Corrosive Environment

Crystals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 338
Author(s):  
Franjo Kozina ◽  
Zdenka Zovko Brodarac ◽  
Sandra Brajčinović ◽  
Mitja Petrič
Keyword(s):  
Engineering Properties ◽  
Corrosive Environment ◽  
Transportation Industry ◽  
Free Zone ◽  
Β Phase ◽  
Thermo Calc Software ◽  
Aluminum Lithium ◽  
Δ Phase ◽  
Mechanical Properties And Corrosion ◽  
Equilibrium Phases

The utilization of aluminum-lithium-magnesium (Al-Li-Mg) alloys in the transportation industry is enabled by excellent engineering properties. The mechanical properties and corrosion resistance are influenced by the microstructure development comprehending the solidification of coherent strengthening precipitates, precipitation of course and angular equilibrium phases as well as the formation and widening of the Precipitate-free zone. The research was performed to determine the microstructure degradation of Al-2.18Mg-1.92Li alloy in a corrosive environment using electrochemical measurements. The solidification sequence of the Al-2.18Mg-1.92Li alloy, obtained using Thermo–Calc software support, indicated the transformation of the αAl dendritic network and precipitation of AlLi (δ), Al2LiMg (T), and Al8Mg5 (β) phase. All of the phases are anodic with respect to the αAl enabling microstructure degradation. To achieve higher microstructure stability, the sample was solution hardened at 520 °C. However, the sample in as-cast condition showed a lower corrosion potential (−749.84 mV) and corrosion rate (17.01 mm/year) with respect to the solution-hardened sample (−752.52 mV, 51.24 mm/year). Higher microstructure degradation of the solution-hardened sample is a consequence of δ phase precipitation at the grain boundaries and inside the grain of αAl, leading to intergranular corrosion and cavity formation. The δ phase precipitates from the Li and Mg enriched the αAl solid solution at the solution-hardening temperature.

Effect of Strain Amounts on Cold Compression Deformation Mechanism of Ti-55531 Alloy with Bimodal Microstructure

2021 ◽  
Vol 1035 ◽  
pp. 182-188
Author(s):  
Jian Hua Cai ◽  
She Wei Xin ◽  
Lei Li ◽  
Lei Zou ◽  
Hai Ying Yang ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Deformation Mechanism ◽  
True Strain ◽  
Bimodal Microstructure ◽  
Free Zone ◽  
Β Phase ◽  
Α Phase ◽  
Initial Stage ◽  
Pile Up ◽  
Dislocation Tangle

The plastic deformation mechanism of Ti-55531 alloy with bimodal microstructure was investigated by compression testing at room temperature. The bimodal microstructure was composed of equiaxed primary α phase (αp) and transformed β (βtrans) that consisted of acicular secondary α phase (αs) and residual β phase (βr). In the initial stage of deformation, the αp grains first underwent plastic deformation, the dislocations germinated and increased, forming the dislocation loop with the dislocation free zone in αp at the true stain of 0.083. With the true strain subsequently increasing to 0.105, the dislocation tangle and dislocation pile-up occurred in αp, and a lot of dislocations were also activated in most of αs. Moreover, the dislocation density was increasing gradually in βr with the adding of strain. Finally, the dislocation pile-up and dislocation tangle appeared in αs and βr at the true strain of 0.163. The whole deformation process was coordinated by αp, αs and βr. They accommodated mutually and completed deformation together.

Investigation of the Structure and Distribution of Chemical Elements between the Phases of Hard Alloys of the Cr3C2-Ti System, Obtained at Various Modes of Explosive Compaction

2020 ◽  
Vol 992 ◽  
pp. 487-492
Author(s):  
V.O. Kharlamov ◽  
Aleksandr Vasilevich Krokhalev ◽  
S.V. Kuz’min ◽  
V.I. Lysak
Keyword(s):  
Phase Composition ◽  
Powder Mixture ◽  
Chemical Interaction ◽  
Chemical Elements ◽  
Equilibrium Phase ◽  
Hard Alloys ◽  
Explosive Compaction ◽  
Thermo Calc Software ◽  
Equilibrium Phases ◽  
Explosive Pressing

The Article presents the findings of the studies of the microstructure, chemical and phase composition of the Cr3C2-Ti system alloys obtained by the explosion. Scanning electron microscopy, energy dispersive and x-ray diffraction analyses were used. The program Thermo-Calc software was used to calculate the equilibrium phases. The phase composition of the compact was shown to fully correspond to that of the initial powder mixture during explosive pressing in the modes of heating from 300 ̊С to 600 ̊С. When heated above 600 ̊С, the chemical interaction of the initial components begins with the formation of new boundary phases. Meanwhile, there is a change in the sample destruction nature and a significant increase in hardness, which points to the hard alloy consolidation. The increase in the powder mixture heating in shock waves to 1000 ̊С leads to intensive macrochemical interaction of the powder mixture components and to formation of an equilibrium phase composition. The established temperature limits determine the most appropriate parameters of shock-wave loading when producing hard alloys by explosive pressing.

Processing of high strength Mg–9Gd–3Nd–1Sn–1Zn–0.6Zr alloy by hot rolling and subsequent aging

2020 ◽  
Vol 10 (7) ◽  
pp. 1020-1031
Author(s):  
Zehua Yan ◽  
Yandong Yu ◽  
Yanchao Sang ◽  
Yiming Yao ◽  
Jiahao Qian
Keyword(s):  
Grain Boundary ◽  
Aging Time ◽  
Hot Rolling ◽  
Aging Treatment ◽  
High Strength ◽  
Subsequent Aging ◽  
Free Zone ◽  
Treatment Conditions ◽  
Peak Aging ◽  
Equilibrium Phases

Magnesium alloy plates can be strengthened by rolling, however, it is easy to crack or even break when the reduction of Mg–RE alloys is too large. Herein, the strengthening mechanical of the Mg–9Gd–3Nd–1Sn–1Zn– 0.6Zr alloy under different treatment conditions were investigated after hot-rolling to 80% reduction in thickness (0.8 mm) by multi-step methods. Furthermore, the rolled alloy by aging strengthening are explored. The results show that the hot-rolled alloy with 80% reduction are basically composed of dynamically recrystallized grains with the size of about 60 m, improving the mechanical properties significantly. The precipitates within grains undergo SSSS→ β″ → β′ phase transformation with the aging treatment up to 200 °C. Fine β″ precipitates were found in the grains of the rolled alloy under aged time (2 h), while β″ precipitates changed into β′ phase when the aging time was extended to 32 h. The base phase which is perpendicular to phase was precipitated in the alloy in longer aging time (96 h). In addition, the thickness of precipitates and precipitation-free zone (PFZ) at the grain boundary gradually increased as the time went on. Meanwhile, the discontinuous equilibrium phases at the grain boundary are gradually become continuous. The ultimate tensile strength and hardness were reached to 431.14 MPa, 105.9 HV at peak-aging, in addition, the elongation is reached to 3.11%, respectively. The formation of crack sources is due to the stress concentration between the brittle PFZ and the magnesium matrix, which leads to the decrease of ductility.

Behavior of β(Mg17Al12) Phases in Mg-Al Alloy Subject to Cycling Cryogenic Treatment

2013 ◽  
Vol 575-576 ◽  
pp. 390-393 ◽  
Author(s):  
Guirong Li ◽  
Hong Ming Wang ◽  
Yun Cai ◽  
Xue Ting Yuan
Keyword(s):  
Cryogenic Treatment ◽  
Weight Percent ◽  
Al Alloy ◽  
Β Phase ◽  
The Matrix ◽  
Thermo Calc Software ◽  
And Performance ◽  
And Behavior ◽  
Microstructure And Performance ◽  
Electronic Microscope

In Mg-Al alloy β (Mg17Al12) phase is the main precipitate and reinforced phase. The microstructure and performance of alloy are strongly dependent on the morphology and behavior of β phases. In this paper, a kind of Mg-Al alloy is chosen as the research object with 8.92 weight percent aluminum element. The alloy is subjected to cycling cryogenic treatment. The microstructure evolution and thermodynamic balance are analyzed by scanning electronic microscope and Thermo-CALC software. The results show that after two cryogenic treatments the quantity of the precipitate hardening β phase increases and the sizes of the precipitates are refined from 8~10 μm to 2~4μm. This is expected to be due to the decreased solubility of aluminum in the matrix at low temperatures and the significant plastic deformation due to internal differences in thermal contraction between phases and grains.

The thermodynamics of mixed crystals of ammonium chloride and ammonium bromide. - III. The heat capacity from 8 to 300 K of solid solutions of composition NH 4 Br 0.20 Cl 0.80 and NH 4 Br 0.74 Cl 0.26

1981 ◽  
Vol 375 (1762) ◽  
pp. 351-359
Keyword(s):  
Heat Capacity ◽  
Ammonium Chloride ◽  
Solid Solutions ◽  
Mixed Crystal ◽  
Mixed Crystals ◽  
Ammonium Bromide ◽  
Ammonium Ions ◽  
Β Phase ◽  
Δ Phase ◽  
Entropy Of Transition

The heat capacity of the mixed crystals NH 4 Br 0.20 CI 0.80 and NH 4 Br 0.74 CI 0.26 has been measured from ca . 8 to 300 K. The first of these solids has, as expected, two gradual transitions, the lower having an entropy of transition ∆ S λ of 3.79 J K –1 mol –1 , and the upper a ∆ S λ of 4.51 J K –1 mol –1 . The heat capacity between these two transitions is always considerably above the ‘normal’ or baseline value, and it appears that the orientational disordering of the ammonium ions, while completed in the γ → β transition, commences in the δ-phase. The other, bromide-rich mixed crystal shows no sign of a δ → γ transition, but has a λ -type γ → β transition which culminates at 262.5 K, with ∆ S λ = 7.31 J K –1 mol –1 . The heat capacity of both mixed crystals in the β-phase, like that of the pure components, is ‘anomalously’ high, the additional heat capacity for the solid solutions being larger than that for the pure salts. The phase diagram for the ammonium-chloride–ammonium-bromide system is shown; it combines previous information with that provided by the heat-capacity results reported in this and previous papers.

Phase Diagram Calculation and Experimental Study on the New Type Mg-Al-Zn-Ca-Sr Alloy in the Mg-Rich Region

2010 ◽  
Vol 650 ◽  
pp. 246-252 ◽  
Author(s):  
Su Qin Luo ◽  
Ai Tao Tang ◽  
Fu Sheng Pan ◽  
Yi Chen ◽  
Zhong Xue Feng
Keyword(s):  
Phase Diagram ◽  
Equilibrium Phase ◽  
Solidification Process ◽  
Secondary Phase ◽  
Calculated Phase Diagram ◽  
Rich Region ◽  
Thermo Calc Software ◽  
Calculation Results ◽  
New Type ◽  
Equilibrium Phases

Calculated phase diagram reveals important phase details for a new type muti-component magnesium alloy. Isothermal sections at 25°C of Mg-Ca-Sr, , Mg-2.74Al-Ca-Sr, Mg-2.74Al-0.79Zn-Ca-Sr system in the Mg-rich region were calculated using CALPHAD method, Thermo-Calc software and Mg-Al-Zn-Ca-Sr quinary database. The equilibrium phase composition in the Mg-rich region was analyzed. The equilibrium phases and solidification process of Mg-2.74Al-0.79Zn-0.68Ca-0.03Sr quinary alloy was calculated. The calculation results were consistent with the experimental results of SEM-EDX analysis and DSC spectrum. The solidification process of Mg-2.74Al-0.79Zn-0.68Ca-0.03Sr quinary alloy is as follow : α-Mg precipitates at 621°C, secondary phase C15-Al2(Ca, Sr) and Gamma-Mg17Al12 precipitate at around 520°C and 160°C in sequence, A4B-(Al4Ca,Al4Sr) may precipitate at around 460°C.

scholarly journals Role of magnesium and minor zirconium on the wear behavior of 5xxx series aluminum alloys under different environments

2020 ◽  
Vol 4 (3) ◽  
pp. 209-220
Author(s):  
Mohammad Salim Kaiser ◽  
Mohammad Abdul Matin ◽  
Kazi Mohammad Shorowordi
Keyword(s):  
Aluminum Alloys ◽  
Fracture Surface ◽  
Wear Behavior ◽  
Corrosive Environment ◽  
Ambient Conditions ◽  
Saline Environment ◽  
Β Phase ◽  
Pin On Disk ◽  
Film Lubrication

The tribological performance of 5xxx series aluminum alloys with ternary zirconium is evaluated at ambient conditions under dry, wet and saline environment. The experiment has been done using a Pin-on-Disk apparatus under an applied load of 20N. The sliding distances varies ranging from 116m-2772m at a sliding velocity of 0.385 ms-1. The results show that presence of Mg and Zr into this alloy helps to increase their strength and wear resistance under dry sliding condition. But they significantly suffer under wet and corrosive environment due to formation of β-phase Al3Mg2, to slip bands and grain boundaries which may lead to and stress-corrosion cracking. The variation of friction coefficient is observed in wet and corrosive environment due to the formation of oxidation film, lubrication, and corrosion action in solution. The SEM fracture surface shows that brittle Al3Mg2 phase initiate the brittle fracture surface for Al-Mg alloy and Zr addition accelerate the brittleness of the alloy owing the fine precipitates of Al3Zr.

Calculation of Aluminum Equivalent Based on Thermo-Calc Software in Ti-Al-Nb Ternary System

2014 ◽  
Vol 788 ◽  
pp. 144-149 ◽  
Author(s):  
Hui Min Yang ◽  
Liang Shun Luo ◽  
Mei Hui Song ◽  
Hai Qun Qi ◽  
Chun Yan Wang ◽  
...  
Keyword(s):  
Phase Diagram ◽  
Ternary Phase ◽  
Ternary Phase Diagram ◽  
Primary Phase ◽  
Ternary Alloys ◽  
Al Content ◽  
Β Phase ◽  
Thermo Calc Software ◽  
Vertical Sections ◽  
Aluminum Equivalent

Ti-Al-Nb ternary phase diagrams were calculated by Thermo-Calc software. The analysis of the calculated vertical sections of Ti-Al-Nb phase diagram indicated that when Nb content is fixed at 5at.% and Al content is lower than 52.3at.%, the primary phase would be β phase during solidification. With 10 at.%Nb and Al content lower than 55.8at.%, or with 15 at.%Nb and Al content lower than 56.9at.%, the primary phase would be β phase. The vertical sections of Ti-Al-Nb ternary phase diagram were further simplified into pseudo-Ti-Al binary phase diagram. According to the pseudo-Ti-Al diagram, the expression of the aluminum equivalent was obtained in Ti-Al-5Nb ternary alloys.

A First-Principles Study of Phase Transition of Octahydro-1,3,5,7-Tetranitro-1,3,5,7-Tetrazocine (HMX) under Static Compression

2016 ◽  
Vol 258 ◽  
pp. 33-36
Author(s):  
Lei Zhang ◽  
Sheng Li Jiang ◽  
Jun Chen
Keyword(s):  
Phase Transition ◽  
First Principles ◽  
Condensed Matter ◽  
Interaction Energies ◽  
Static Compression ◽  
Molecular Systems ◽  
Β Phase ◽  
Equation Of States ◽  
Structure Of Molecules ◽  
Δ Phase

The issue of HMX phase transition under hydrostatic compression is not clear and experiments show conflicting results. Effective solution via first-principles simulation is challenged by difficulty of accurate prediction of Van der Waals interaction, which exists ubiquitously and is crucial for determining the structure of molecules and condensed matter. We have contributed to this by constructing a set of pseudopotentials and pseudoatomic orbital basis, specialized for molecular systems with C/H/N/O elements. The reliability of the method is verified from the interaction energies of 45 complexes (comparing to the results of coupled cluster with singles and doubles (Triple) (CCSD)(T)) and the crystalline structures of 7 typical explosives (comparing to experiments). Using this method, we complete the phase diagram of HMX under static compression up to 50 GPa. We make it clear that no β→δ/ε→δ phase transition occurs at 27 GPa, which has long been a hot debate in experiments. A possible γ→β phase transition is found at around 2.10 GPa in the environment of vapour. We have also predicted the equation of states for α-, δ-, and γ-HMX, which are experimentally absent.

Microstructure and Mechanical Properties and Corrosion Behavior of Ti-Mo-Sn Alloys

2007 ◽  
Vol 348-349 ◽  
pp. 281-284
Author(s):  
Yu Feng Zheng ◽  
Yan Bo Wang
Keyword(s):  
Mechanical Properties ◽  
Tensile Test ◽  
Corrosion Behavior ◽  
Electrochemical Measurement ◽  
Xrd Analysis ◽  
Test Results ◽  
Β Phase ◽  
Measurement Results ◽  
Mechanical Properties And Corrosion ◽  
Minor Content

The phase constitution, mechanical properties, and corrosion behavior of TiMoSn alloys were investigated by means of XRD, tensile test, electrochemical measurement and XPS techniques. The XRD analysis results showed that at room temperature TiMoSn alloys are mainly composed of β phase, with minor content of α" phase, in as-cast and solid solution treated conditions. The tensile test results indicate that the elastic moduli of the Ti-Mo-Sn alloys are in the range of 52~74GPa. The electrochemical measurement results indicate that TiMoSn alloys have excellent corrosion resistance in simulated body fluid. The XPS analysis results reveal that the passive films of TiMoSn alloys after polarization consist of TiO2, SnO2 and Mo2O5.

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