scholarly journals Development from Alloys to Nanocomposite for an Enhanced Mechanical and Ignition Response in Magnesium

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1792
Author(s):  
Khin Sandar Tun ◽  
Tan Yan Shen Brendan ◽  
Sravya Tekumalla ◽  
Manoj Gupta
Keyword(s):  
Federal Aviation Administration ◽  
Specific Yield ◽  
Compositional Variation ◽  
Potential Candidate ◽  
Compressive Properties ◽  
Alloying Element ◽  
Grain Sizes ◽  
B4c Nanoparticles ◽  
Lightweight Engineering ◽  
Evolution Of Microstructure

The current study reports on the evolution of microstructure, variations in compressive properties and the ignition resistance of Mg through compositional variation, using alloying elements and nanoreinforcement. The alloys were designed with the use of a singular alloying element, Ca, and a binary alloying element, Ca+Sc, to develop Mg1Ca (wt.%) and Mg1Ca1Sc (wt.%) alloys. B4C nanoparticles were addedas the reinforcement phase in the Mg1Ca1Sc alloy to create the Mg1Ca1Sc/1.5B4C (wt.%) nanocomposite. The most effective compressive properties and level of ignition resistance was displayed by the developed composite. The grain sizes were significantly reduced in the Mg alloys (81%) and the composite (92%), compared with that of the Mg. Overall, the microstructural features (i.e., grain refinement, the formation of favorable intermetallic compounds, and hard reinforcement particles with an adequate distribution pattern) enhanced both the compressive strength and strain of the alloys and the composite. The ignition resistance was progressively increased from the alloys to the nanocomposite, and a peak ignition temperature of 752 °C was achieved in the composite. When compared with the ignition resistant of Elektron 21 (E21) alloy, which met the Federal Aviation Administration (FAA) requirements, the Mg1Ca1Sc/1.5B4C nanocomposite showed a higher specific yield strength and better ignition resistance, asserting it as a potential candidate material for lightweight engineering applications, including aerospace and defense sectors.

Bacterial influence on the formation of hematite: implications for Martian dormant life

2021 ◽  
pp. 1-15
Author(s):  
Sudeera Wickramarathna ◽  
Rohana Chandrajith ◽  
Atula Senaratne ◽  
Varun Paul ◽  
Padmanava Dash ◽  
...  
Keyword(s):  
Inductively Coupled Plasma ◽  
Soil Layer ◽  
Soil Samples ◽  
Mineral Weathering ◽  
Compositional Variation ◽  
Rrna Gene ◽  
Potential Candidate ◽  
Metabolic Processes ◽  
Extraterrestrial Life ◽  
X Ray

Abstract Previous exploration missions have revealed Mars as a potential candidate for the existence of extraterrestrial life. If life could have existed beneath the Martian subsurface, biosignatures would have been preserved in iron-rich minerals. Prior investigations of terrestrial biosignatures and metabolic processes of geological analogues would be beneficial for identifying past metabolic processes on Mars, particularly morphological and chemical signatures indicative of past life, where biological components could potentially be denatured following continued exposure to extreme conditions. The objective of the research was to find potential implications for Martian subsurface life by characterizing morphological, mineralogical and microbial signatures of hematite deposits, both hematite rock and related soil samples, collected from Highland Complex of Sri Lanka. Rock samples examined through scanning electron microscopy-energy dispersive X-ray (SEM-EDX) spectroscopy. Analysis showed globular and spherical growth layers nucleated by bacteria. EDX results showed a higher iron to oxygen ratio in nuclei colonies compared to growth layers, which indicated a compositional variation due to microbial interaction. X-ray diffraction analysis of the hematite samples revealed variations in chemical composition along the vertical soil profile, with the top surface soil layer being particularly enriched with Fe2O3, suggesting internal dissolution of hematite through weathering. Furthermore, inductively coupled plasma-mass spectrometry analyses carried out on both rock and soil samples showed a possible indication of microbially induced mineral-weathering, particularly release of trapped trace metals in the parent rock. Microbial diversity analysis using 16S rRNA gene sequencing revealed that the rock sample was dominated by Actinobacteria and Proteobacteria, specifically, members of iron-metabolizing bacterial genera, including Mycobacterium, Arthrobacter, Amycolatopsis, Nocardia and Pedomicrobium. These results suggest that morphological and biogeochemical clues derived from studying the role of bacterial activity in hematite weathering and precipitation processes can be implemented as potential comparative tools to interpret similar processes that could have occurred on early Mars.

Compressive properties of Cu with different grain sizes: sub-micron to nanometer realm

2008 ◽  
Vol 43 (9) ◽  
pp. 3305-3313 ◽  
Author(s):  
Akhtar S. Khan ◽  
Babak Farrokh ◽  
Laszlo Takacs
Keyword(s):  
Compressive Properties ◽  
Grain Sizes

scholarly journals Textural and compositional variation of sand along the Manahara-Bagmati river basin, Kathmandu Valley

2001 ◽  
Vol 23 ◽  
Author(s):  
Naresh Kazi Tamrakar ◽  
Hari Nandan Gurmaita
Keyword(s):  
River Basin ◽  
River System ◽  
Compositional Variation ◽  
Humid Climate ◽  
Quartz Content ◽  
Rock Fragments ◽  
Grain Sizes ◽  
Size Grade ◽  
The Mean ◽  
Bagmati River

The Manahara-Bagmati river basin is located in a humid climate and has a 51 km long low gradient profile. It collects sediments from metamorphic, metasedimentary, and fluvio-lacustrine sources. The sediment samples collected from 17 localities were studied texturally and compositionally to infer how sediment modifies due course of transport and whether the trends are interfered by mixing, recycling, and weathering. For this purpose, two size grades (i.e., 0-1ϕ and 2-3ϕ) were studied. Between them, the trends were more conspicuous in the 0-1ϕ sand grade. Mean (M2) and median (M6) grain sizes increase downstream exponentially. Sorting (σ1) also improves along the river course. Quartz content gradually increases downstream, whilst feldspars and rock fragments decrease remarkably along the river course.  Rapid dilution of feldspars and rock fragments (from coarser size grade) occurs after 27 km of transport. The Modified Maturity Index, which ranges from 19.8 to 214, increases from the Manahara to Bagmati River sands. The mica content in the Bagmati River is from 2 to 8 times higher than in the Manahara River. Within the studied river course, the mean projection sphericity (ψp) of quartz remains high (0.80 in average) but does not show any consistent trend. The mean roundness (ρ) of the 0-1ϕ sand grade increases conspicuously against the distance of transport. The majority of samples belong to submature class. Local influx of sediments and recycling are profound from Sankhu to Sanothimi and from Chobhar to Hasdol. Rapid weathering of labile grains is inferred in the middle reach of the Manahara- Bagmati river system (i.e., between Sanothimi and Chobhar).

scholarly journals Compressive Properties of A2024 Alloy Foam Fabricated through a Melt Route and a Semi-Solid Route

Metals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 153 ◽  
Author(s):  
Takashi Kuwahara ◽  
Taro Osaka ◽  
Mizuki Saito ◽  
Shinsuke Suzuki
Keyword(s):  
Grain Size ◽  
Absorption Efficiency ◽  
S Phase ◽  
Compressive Properties ◽  
Alloying Element ◽  
Plateau Stress ◽  
Energy Absorption Efficiency ◽  
Semi Solid ◽  
Primary Crystals ◽  
Solid Temperature

A2024 alloy foams were fabricated by two methods. In the first method, the melt was thickened by Mg, which acts as an alloying element (melt route). In the second method, the melt was thickened by using primary crystals at a semi-solid temperature with a solid fraction of 20% (semi-solid route). A2024 alloy foams fabricated through the semi-solid route had coarse and uneven pores. This led to slightly brittle fracture of the foams, which resulted in larger energy absorption efficiency than that of the foams fabricated through the melt route. Moreover, A2024 alloy foams fabricated through the semi-solid route had a coarser grain size because of the coarse primary crystals. However, by preventing the decrease in the alloying element Mg, the θ/θ’ phase was suppressed. Additionally, by preventing the precipitation of the S′ phase, the amount of Guinier-Preston-Bagaryatsky (GPB) zone increased. This resulted in a larger plateau stress.

Evolution of microstructure and hardness in a dual-phase Al0.5CoCrFeNi high-entropy alloy with different grain sizes

Rare Metals ◽  
2019 ◽  
Vol 39 (2) ◽  
pp. 156-161 ◽  
Author(s):  
Hao-Xue Yang ◽  
Jin-Shan Li ◽  
Tong Guo ◽  
William-Yi Wang ◽  
Hong-Chao Kou ◽  
...  
Keyword(s):  
High Entropy Alloy ◽  
Dual Phase ◽  
High Entropy ◽  
Grain Sizes ◽  
Evolution Of Microstructure

scholarly journals SHS Synthesis, SPS Densification and Mechanical Properties of Nanometric Tungsten

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 252
Author(s):  
Sarah Dine ◽  
Elodie Bernard ◽  
Nathalie Herlin ◽  
Christian Grisolia ◽  
David Tingaud ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Cooling System ◽  
Second Phase ◽  
Alloying Element ◽  
Pure Tungsten ◽  
Powder Synthesis ◽  
Grain Sizes ◽  
Chromium Alloys ◽  
Current Production ◽  
Strength And Ductility

Recent studies have shown that low grain sizes are favorable to improve ductility and machinability in tungsten, as well as a resistance to ablation and spallation, which are key properties for the use of this material in a thermonuclear fusion environment (Tokamaks such as ITER). However, as one of the possible incidents during Tokamak operation is the leakage of air or water from the cooling system inside the chamber, resulting in the so-called loss of vacuum accident (LOVA), extensive oxidation may arise on tungsten components, and the use of an alloy with improved oxidation resistance is therefore highly desirable. As current production routes are not suitable for the fabrication of bulk nanostructured tungsten or tungsten alloys samples, we have proposed a new methodology based on powder metallurgy, including the powder synthesis, the densification procedure, and preliminary mechanical testing, which was successfully applied to pure tungsten. A similar study is hereby presented on tungsten-chromium alloys with up to 6 wt.% Cr. Results show that full tungsten densification may be obtained by SPS at a temperature lower than 1600 °C. The resulting morphology strongly depends on the amount of the alloying element, presenting a possible second phase of chromium oxide, but always keeps a partial nanostructure inherited from the synthesized powders. Such microstructure had previously been identified as being favorable to the use of these materials in fusion environments and for improved mechanical properties, including hardness, yield strength and ductility, all of which is confirmed by the present study.

Improvement of Compressive Properties of Porous HA Scaffold by Introducing PCL Secondary Phase

2013 ◽  
Vol 858 ◽  
pp. 96-102 ◽  
Author(s):  
Phanny Yos ◽  
Mitsugu Todo
Keyword(s):  
Fracture Property ◽  
Secondary Phase ◽  
Solution Concentration ◽  
Template Method ◽  
Potential Candidate ◽  
Compression Tests ◽  
Compressive Properties ◽  
Composite Scaffolds ◽  
Two Phase ◽  
Porous Hydroxyapatite

Continuous porous hydroxyapatite (HA) scaffold has been considered to be used in bone tissue engineering. However, the low fracture property of HA scaffold has been a problem to be solved. In the present study, polycaprolactone (PCL) was introduced as a secondary phase into the porous structure of HA scaffold to improve the low fracture property. HA scaffolds were firstly fabricated using the template method. The HA scaffolds were then coated with PCL by changing the solution concentration from 1 to 5 wt%. Compression tests and SEM were done to examine the mechanical properties and the morphology of the two-phase composite scaffolds. It was found that the compression strength and modulus increased with increasing PCL concentration. It is also noted that PCL coating can greatly improve the brittleness of pure HA scaffolds. XRD test was also done to study the phase stability of HA and the two-phase scaffolds. There was no chemical reaction between PCL and HA observed by the XRD results. On the overall, these results indicated that PCL coating can effectively improve the low fracture property of pure HA scaffold and the two-phase scaffold could be a potential candidate for bone regeneration.

scholarly journals Evolution of Microstructure and Precipitation in Heat-Treatable Aluminium Alloys during ECA Pressing and Subsequent Heat Treatment

2006 ◽  
Vol 503-504 ◽  
pp. 275-280 ◽  
Author(s):  
Nong Gao ◽  
Marco J. Starink ◽  
Minoru Furukawa ◽  
Z. Horita ◽  
Cheng Xu ◽  
...  
Keyword(s):  
Thermal Effects ◽  
Hardness Testing ◽  
Scanning Calorimetry ◽  
Grain Sizes ◽  
Angular Pressing ◽  
2024 Alloy ◽  
Transmission Electron ◽  
Evolution Of Microstructure ◽  
Al 2024 ◽  
Microstructural Examination

The precipitation and evolution of microstructure in a spray-cast Al-7034 alloy and a commercial wrought Al-2024 alloy were studied after equal-channel angular pressing (ECAP) using transmission electron microscopy and differential scanning calorimetry (DSC). Microstructural examination showed the grain sizes of both alloys were reduced to the range of ~0.3–0.5 μm through ECAP. The DSC analysis identified the occurrence of thermal effects involving the formation, coarsening, dissolution and melting of the precipitate phases and concurrent recrystallization. The heating and ageing response of the alloys processed by ECAP was identified by micro-hardness testing of the samples after interrupted heating and ageing treatments.

scholarly journals Superior Properties of Ultra-fine-grained Steels

10.14311/572 ◽  
2004 ◽  
Vol 44 (3) ◽  
Author(s):  
J. I. Leinonen
Keyword(s):  
Control Process ◽  
Rolling Process ◽  
Potential Candidate ◽  
Test Results ◽  
Fine Grained ◽  
Grain Sizes ◽  
Hot Rolling Process ◽  
Potential Applications ◽  
New Generation ◽  
Fine Grained Steels

A description of the improved mechanical properties obtained in ultra-fine-grained steels up to now will be presented in this paper, and some potential applications of these new generation steels will be described. In addition, the principle and implementation of a novel hot rolling process developed by the author will be introduced. This novel Thermomechanical Nonrecrystallisation Control Process (TNCP) has been shown to give an ultra-fine ferrite (uff) structure with grain sizes of 2 to 3mm in various test steels, thus resulting in super-toughness. Charpy V impact test results suggest that some of these steels could still be tough at temperatures lower than -100 °C. This novel process, TNCP, is one potential candidate for the commercial production of superior ultra-fine-grained steels in the future.

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