scholarly journals Effect of Pretreatment and Cryogenic Temperatures on Mechanical Properties and Microstructure of Al-Cu-Li Alloy

Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 4873
Author(s):  
Cheng Wang ◽  
Jin Zhang ◽  
Youping Yi ◽  
Chunnan Zhu
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Hot Deformation ◽  
Electron Backscatter Diffraction ◽  
Coarse Grained ◽  
Second Phase ◽  
Strengthening Effect ◽  
Cryogenic Temperatures ◽  
Transmission Electron ◽  
Strength And Ductility

The mechanical properties of Al-Cu-Li alloys after different pretreatments were investigated through tensile testing at 25 and −196 °C, and the corresponding microstructure characteristics were obtained through optical metallography, scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy. An increasing mechanism of both strength and ductility at cryogenic temperatures was revealed. The results show that the hot deformation pretreatment before homogenization promoted the precipitation of Al3Zr particles, improved particle distribution, and inhibited local precipitation-free zones (PFZ). Both hot deformation pretreatment before homogenization and cryogenic temperature were able to improve strength and ductility. The former improved strength by promoting the precipitation of Al3Zr particles while enhancing the strengthening effect of the second-phase particles and reducing the thickness of the coarse-grained layer. Meanwhile, the increase in ductility is attributable to the decrease in thickness of the coarse-grained layer, which reduced the deformation incompatibility between the coarse and fine grains and increased the strain-hardening index. The latter improved the strength by suppressing dynamic recovery during the deformation process, increasing the dislocation density, and enhancing the work hardening effect. Additionally, the increase in ductility is attributable to the suppression of planar slip and strengthening of grain boundaries, which promoted the deformation in grain interiors and made the deformation more uniform.

Microstructure and mechanical properties of 15-5 PH stainless steel under different aging temperature

2021 ◽  
Vol 118 (6) ◽  
pp. 601
Author(s):  
Chunhui Jin ◽  
Honglin Zhou ◽  
Yuan Lai ◽  
Bei Li ◽  
Kewei Zhang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Aging Temperature ◽  
Electron Backscatter Diffraction ◽  
Lath Martensite ◽  
Optical Microscope ◽  
Second Phase ◽  
Strengthening Mechanisms ◽  
Microstructure And Mechanical Properties ◽  
Transmission Electron

The influence of aging temperature on microstructure and mechanical properties of Cr15Ni5 precipitation hardening stainless steel (15-5 PH stainless steel) were investigated at aging temperature range of 440–610 °C. The tensile properties at ambient temperature of the 15-5 PH stainless steel processed by different aging temperatures were tested, and the microstructural features were further analyzed utilizing optical microscope (OM), transmission electron microscope (TEM), electron backscatter diffraction (EBSD) as well as X-ray diffraction (XRD), respectively. Results indicated the strength of the 15-5 PH stainless steel was firstly decreased with increment of aging temperature from 440 to 540 °C, and then increased with the increment of aging temperature from 540 to 610 °C. The strength and ductility were well matched at aging temperature 470 °C, and the yield strength, tensile strength as well as elongation were determined to be 1170 MPa, 1240 MPa and 24%, respectively. The microstructures concerning to different aging temperatures were overall confirmed to be lath martensite. The strengthening mechanisms induced by dislocation density and the second phase precipitation of Cu-enriched metallic compound under different aging temperatures were determined to be the predominant strengthening mechanisms controlling the variation trend of mechanical properties corresponding to different aging temperatures with respect to 15-5 PH stainless steel.

scholarly journals Research on the Microstructures and Mechanical Properties of Bainite/Martensite Rail Treated by the Controlled-Cooling Process

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3061 ◽  
Author(s):  
Jiajia Qiu ◽  
Min Zhang ◽  
Zhunli Tan ◽  
Guhui Gao ◽  
Bingzhe Bai
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Tensile Strength ◽  
Impact Toughness ◽  
Electron Backscatter Diffraction ◽  
Microstructural Characterization ◽  
Cooling Process ◽  
Controlled Cooling ◽  
Transmission Electron ◽  
Backscatter Diffraction

A bainite/martensite multiphase rail is treated by the controlled-cooling process with different finish-cooling temperatures. The simulated temperature–time curves of the position of 5 mm and 15 mm below the rail tread (P5 and P15) express different trends. P5 has greater impact toughness and lower tensile strength than P15. Microstructural characterization was carried out by conducting scanning electron microscopy, X-ray diffraction, electron backscatter diffraction, and transmission electron microscopy. The greater tensile strength is due to the dispersed ε-carbides hindering the movement of dislocations. The greater impact toughness is attributed to the filmy retained austenite and the smaller effective grain with high-angle boundary. Finite element modeling (FEM) and microstructural characterization reasonably explain the changes of mechanical properties. The present work provides experimental and theoretical guidance for the development of rail with excellent mechanical properties.

scholarly journals Strengthening of a Near β-Ti Alloy through β Grain Refinement and Stress-Induced α Precipitation

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4255 ◽  
Author(s):  
Wei Chen ◽  
Chao Li ◽  
Kangtun Feng ◽  
Yongcheng Lin ◽  
Xiaoyong Zhang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
High Strength ◽  
Ti Alloy ◽  
Β Phase ◽  
Ti Alloys ◽  
Α Phase ◽  
Transmission Electron ◽  
Strength And Ductility ◽  
Α Particles

Near β-Ti alloys with high strength and good ductility are desirable for application in aviation and aerospace industries. Nevertheless, strength and ductility are usually mutually exclusive in structural materials. Here we report a new thermo-mechanical process, that is, the alloy was cross-rolled in β field then aged at 600 °C for 1 h. By such a process, a high strength (ultimate tensile strength: 1480 MPa) and acceptable ductility (elongation: 10%) can be simultaneously achieved in the near β-Ti alloy, based on the microscale β matrix and nanoscale α phase. The microstructure evolution, mechanical properties and strengthening mechanisms have been clarified by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that the grain size of the β phase progressively decreased with the increasing of rolling reduction. Moreover, dense dislocation structures and martensite phases distributed in the cross-rolled β matrix can effectively promote the precipitation of nanoscale α particles. TEM analyses confirmed that a heat-treatment twin was generated in the newly formed α lath during aging. These findings provide insights towards developing Ti alloys with optimized mechanical properties.

The Structure and Properties of MoSi2-Mo5Si3 Composites

1992 ◽  
Vol 273 ◽  
Author(s):  
H. Kung ◽  
D. P. Mason ◽  
A. Basu ◽  
H. Chang ◽  
D. C. Van Aken ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Transmission Electron Microscopy ◽  
High Temperature ◽  
Second Phase ◽  
Structure And Properties ◽  
Transmission Electron ◽  
Interfacial Structures ◽  
Two Phases ◽  
Hardness Values

ABSTRACTThe addition of Mo5Si3 as a reinforcing second phase in a MoSi2 matrix has been investigated for possible high temperature strengthening effects. MoSi2 with up to 45 vol % Mo5Si3 was fabricated using powder metallurgy (PM) and arc-casting (AC) techniques. Effects of processing routes, which result in different microstructures, on their mechanical properties are given. PM composites, which have an equiaxed microstructure, exhibit a limited increase in hardness. Higher hardnesses are observed in script-structured AC eutectics and Er-modifiedeutectics throughout the temperatures studied (25–1300°C). Crack propagation paths induced by indentation show long transphase cracks in the AC materials vs short intergranular and interphase cracks in the PM composites at high temperatures.Transmission electron microscopy discloses that the interface in the AC composites has a low-index orientation relationship between the two phases and shows regularly faceted interfacial structures, while planar interfaces are found in the PM composites. These observations suggest the interface is stronger and lower in energy in the AC composites, which is consistent with the higher hardness values and long transphase cracks observed.Dislocation analysis shows the presence of ordinary dislocations (<100>, <110> and 1/2<111>) in MoSi2 in the as-fabricated composites. These types of dislocation are also responsible for the high temperature plastic deformation in compression in both the monolithic MoSi2 and the composites. <331> types of dislocation are only found in MoSi2 either near the interface of the AC composites or in materials deformed below 1000°C.

scholarly journals Effects of Different Heat Treatments on Mechanical Properties and Corrosion Resistance of Al-7.95Zn-1.84Mg-0.65Cu Aluminum Alloy

2020 ◽  
Vol 38 (3) ◽  
pp. 596-603
Author(s):  
Xiuqin Kuang ◽  
Ruilei Li ◽  
Qingqing Ji ◽  
Junjie Jiang ◽  
Man Jin
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Transmission Electron Microscopy ◽  
Corrosion Resistance ◽  
Aluminum Alloy ◽  
Intergranular Corrosion ◽  
Tensile Tests ◽  
Strengthening Effect ◽  
Transmission Electron ◽  
Mechanical Properties And Corrosion

The effects of retrogression and re-aging(RRA) heat treatment on the mechanical properties and corrosion resistance of Al-7.95Zn-1.84Mg-0.65Cu aluminum alloy were investigated by hardness and tensile tests, as well as intergranular corrosion and transmission electron microscopy (TEM). The results show that the Al-7.95Zn-1.84Mg-0.65Cu alloy can obtain better hardness than the single-stage peak aging (T6) process after RRA process (120℃/24 h+200℃/10 min+120℃/24 h). At the same time, the tensile strength is 528.37 MPa, with 13.73% elongation and 29.4% increase in strong plastic product. The electrical conductivity is 40.47% IACS, the intergranular corrosion depth is only 59.43 μm, and the exfoliation corrosion grade is EA. The test results of transmission electron microscopy showed that the η' phase with larger size, greater strengthening effect and more obvious contrast is found in the alloy crystal after RRA treatment, and grain boundary precipitates (GBPs) become more discrete and coarser and precipitation-free precipitated zone (PFZ) becomes wider.

The Formation of Acicular Ferrite and Mechanical Properties Behaviors in a Low Welding Crack Susceptibility Steel

2010 ◽  
Vol 163-167 ◽  
pp. 337-341 ◽  
Author(s):  
Liang Yun Lan ◽  
Chun Lin Qiu ◽  
De Wen Zhao
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Acicular Ferrite ◽  
Electron Backscatter Diffraction ◽  
High Strength ◽  
Accelerated Cooling ◽  
Transmission Electron ◽  
Crystallographic Characteristics ◽  
Backscatter Diffraction ◽  
Crack Susceptibility

The nucleation and crystallographic characteristics of acicular ferrite in the as-rolled and tempered steel were investigated by using an optical microscopy (OM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) equipped with electron backscatter diffraction (EBSD). The results showed that acicular ferrite forms at nucleation sites such as dislocations within austenite grains under the heavy reduction in the austensite non-recrystallization region and accelerated cooling conditions, and the inclusions such as Al2O3•MnS may have promotion effect for the formation of acicular ferrite. Acicular ferrite has high misorientation angle boundaries and a number of sub-boundaries or high density of dislocations inside, which contributes to an excellent combination of high strength and toughness. And the morphology of acicular ferrite does not show obvious change in tempering microstructure due to high temperature thermal stability, which plays an important part in keeping good mechanical properties for tempered specimens.

Microstructural Characterization of Aluminum-Carbon Nanotube Nanocomposites Produced Using Different Dispersion Methods

2016 ◽  
Vol 22 (3) ◽  
pp. 725-732 ◽  
Author(s):  
Sónia Simões ◽  
Filomena Viana ◽  
Marcos A. L. Reis ◽  
Manuel F. Vieira
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Ball Milling ◽  
Electron Backscatter Diffraction ◽  
Microstructural Characterization ◽  
Single Step ◽  
Strengthening Effect ◽  
Transmission Electron ◽  
The Impact

AbstractThis research focuses on characterization of the impact of dispersion methods on aluminum-carbon nanotubes (Al-CNTs) nanocomposite structure. Nanocomposites were produced by a conventional powder metallurgy process after the dispersion of the CNTs on the Al powders, using two approaches: (1) the dispersion of CNTs and mixture with Al powders were performed in a single step by ultrasonication; and (2) the CNTs were previously untangled by ultrasonication and then mixed with Al powders by ball milling. Microstructural characterization of Al-CNT nanocomposites was performed by optical microscopy, scanning and transmission electron microscopy, electron backscatter diffraction, and high-resolution transmission electron microscopy (HRTEM). Microstructural characterization revealed that the use of ball milling for mixing CNTs with Al powders promoted the formation of CNT clusters of reduced size, more uniformly dispersed in the matrix, and a nanocomposite of smaller grain size. However, the results of HRTEM and Raman spectroscopy show that ball milling causes higher damage to the CNT structure. The strengthening effect of the CNT is attested by the increase in hardness and tensile strength of the nanocomposites.

Controlling the Microstructure and Texture Using Multidirectional Forging (MDF) to Develop a Low Corrosion Rate Mg Alloy

CORROSION ◽  
10.5006/3485 ◽  
2020 ◽  
Vol 76 (8) ◽  
pp. 750-765 ◽  
Author(s):  
Ahmad Bahmani ◽  
Kwang Seon Shin
Keyword(s):  
Electron Microscopy ◽  
Corrosion Rate ◽  
Uniform Distribution ◽  
Electron Backscatter Diffraction ◽  
Mg Alloy ◽  
Second Phase ◽  
Compression Tests ◽  
Multidirectional Forging ◽  
Transmission Electron ◽  
Tension And Compression

A new Mg alloy was cast, then extruded, and finally multidirectionally forged (MDF) at 180°C (MDF180) and 300°C (MDF300). The corrosion behavior was evaluated using electrochemical and immersion techniques. The mechanical property was assessed using tension and compression tests. The microstructures were analyzed using optical microscopy, scanning electron microscopy, transmission electron microscopy, x-ray diffraction (XRD), and thermodynamic calculations, while texture was studied by XRD and electron backscatter diffraction. Results indicated that due to grain refinement and good distribution of second phase after MDF, yield strength as well as elongation were improved. The corrosion rates were reduced for MDF180 due to the uniform distribution of the second phase along with uniform distribution of grains. Corrosion rate was more reduced for MDF300 due to dissolution of second phase and elimination of worked grains.

Microstructure, Texture and Property of Interstitial-Free (IF) Steel after Ultra-Fast Annealing

2015 ◽  
Vol 1120-1121 ◽  
pp. 1003-1007 ◽  
Author(s):  
He Long Cai ◽  
Jun Sheng Mou ◽  
Zi Yong Hou
Keyword(s):  
Electron Microscopy ◽  
Electron Backscatter Diffraction ◽  
Second Phase ◽  
Interstitial Free ◽  
If Steel ◽  
Steel Sheets ◽  
Transmission Electron ◽  
Second Phase Particles ◽  
Backscatter Diffraction ◽  
Equiaxed Grain

In this paper, common continous annealing (CCA) and ultra-fast annealing (UFA) were carried out on a cold-rolled interstitial-free (IF) steel, respectively. The microstructure of the annealed IF steel was characterized by means of scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The mechanical property was examined using tensile test. The optimum annealing process parameters were then obtained. The results showed that, the recrystallization occurs at the temperature in the range of 780-830°C. The fraction of equiaxed grain increases with the annealing temperature increasing. The well combination of mechanical properties and formability was obtained when the IF steel annealed at 820°C, which was the result of the fine dispersed second phase particles. {001} texture was absent in the whole thickness of all the annealed IF steels. In addition, the strongest γ texture was found, and this was a potential way to improve the deep drawability of annealed steel sheets.

Phase Transformations in Ti-7w/oMo-3w/oMe Alloy

1974 ◽  
Vol 32 ◽  
pp. 514-515
Author(s):  
S. Fujishiro
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Transmission Electron Microscopy ◽  
Tensile Strength ◽  
Mechanical Processing ◽  
Ray Method ◽  
X Ray ◽  
Transmission Electron ◽  
Water Quench ◽  
Alpha Beta

The mechanical properties of three titanium alloys (Ti-7Mo-3Al, Ti-7Mo- 3Cu and Ti-7Mo-3Ta) were evaluated as function of: 1) Solutionizing in the beta field and aging, 2) Thermal Mechanical Processing in the beta field and aging, 3) Solutionizing in the alpha + beta field and aging. The samples were isothermally aged in the temperature range 300° to 700*C for 4 to 24 hours, followed by a water quench. Transmission electron microscopy and X-ray method were used to identify the phase formed. All three alloys solutionized at 1050°C (beta field) transformed to martensitic alpha (alpha prime) upon being water quenched. Despite this heavily strained alpha prime, which is characterized by microtwins the tensile strength of the as-quenched alloys is relatively low and the elongation is as high as 30%.

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