scholarly journals Crystal Strengths at Micro- and Nano-Scale Dimensions

Crystals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 88
Author(s):  
Ronald W. Armstrong ◽  
Wayne L. Elban
Keyword(s):  
Grain Size ◽  
Present Report ◽  
Crack Size ◽  
Strength Properties ◽  
Indentation Hardness ◽  
Mems Devices ◽  
Iron And Steel ◽  
Nano Scale ◽  
Silicon Crystals ◽  
Dependent Strain

Higher strength levels, achieved for dimensionally-smaller micro- and nano-scale materials or material components, such as MEMS devices, are an important enabler of a broad range of present-day engineering devices and structures. Beyond such applications, there is an important effort to understand the dislocation mechanics basis for obtaining such improved strength properties. Four particular examples related to these issues are described in the present report: (1) a compilation of nano-indentation hardness measurements made on silicon crystals spanning nano- to micro-scale testing; (2) stress–strain measurements made on iron and steel materials at micro- to nano-crystal (grain size) dimensions; (3) assessment of small dislocation pile-ups relating to Griffith-type fracture stress vs. crack-size calculations for cleavage fracturing of α-iron; and (4) description of thermally-dependent strain rate sensitivities for grain size strengthening and weakening for macro- to micro- to nano-polycrystalline copper and nickel materials.

Material grain size and crack size influences on cleavage fracturing

2015 ◽  
Vol 373 (2038) ◽  
pp. 20140124 ◽  
Author(s):  
Ronald W. Armstrong
Keyword(s):  
Grain Size ◽  
Fracture Mechanics ◽  
Crack Size ◽  
Size Dependent ◽  
Silicon Crystals ◽  
Pile Up ◽  
Crack Tip Plasticity ◽  
Material Grain Size ◽  
Stress Behaviour ◽  
Relationship Of

A review is given of the analogous dependence on reciprocal square root of grain size or crack size of fracture strength measurements reported for steel and other potentially brittle materials. The two dependencies have much in common. For onset of cleavage in steel, attention is focused on relationship of the essentially athermal fracture stress compared with a quite different viscoplastic yield stress behaviour. Both grain-size-dependent stresses are accounted for in terms of dislocation pile-up mechanics. Lowering of the cleavage stress occurs in steel because of carbide cracking. For crack size dependence, there is complication of localized crack tip plasticity in fracture mechanics measurements. Crack-size-dependent conventional and indentation fracture mechanics measurements are described also for results obtained on the diverse materials: polymethylmethacrylate, silicon crystals, alumina polycrystals and WC-Co (cermet) composites.

scholarly journals Overview of HSS Steel Grades Development and Study of Reheating Condition Effects on Austenite Grain Size Changes

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1988
Author(s):  
Tibor Kvackaj ◽  
Jana Bidulská ◽  
Róbert Bidulský
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
High Strength Steel ◽  
Single Phase ◽  
Hsla Steel ◽  
High Strength ◽  
Strength Properties ◽  
Austenite Grain Size ◽  
Austenite Grain ◽  
Steel Grades

This review paper concerns the development of the chemical compositions and controlled processes of rolling and cooling steels to increase their mechanical properties and reduce weight and production costs. The paper analyzes the basic differences among high-strength steel (HSS), advanced high-strength steel (AHSS) and ultra-high-strength steel (UHSS) depending on differences in their final microstructural components, chemical composition, alloying elements and strengthening contributions to determine strength and mechanical properties. HSS is characterized by a final single-phase structure with reduced perlite content, while AHSS has a final structure of two-phase to multiphase. UHSS is characterized by a single-phase or multiphase structure. The yield strength of the steels have the following value intervals: HSS, 180–550 MPa; AHSS, 260–900 MPa; UHSS, 600–960 MPa. In addition to strength properties, the ductility of these steel grades is also an important parameter. AHSS steel has the best ductility, followed by HSS and UHSS. Within the HSS steel group, high-strength low-alloy (HSLA) steel represents a special subgroup characterized by the use of microalloying elements for special strength and plastic properties. An important parameter determining the strength properties of these steels is the grain-size diameter of the final structure, which depends on the processing conditions of the previous austenitic structure. The influence of reheating temperatures (TReh) and the holding time at the reheating temperature (tReh) of C–Mn–Nb–V HSLA steel was investigated in detail. Mathematical equations describing changes in the diameter of austenite grain size (dγ), depending on reheating temperature and holding time, were derived by the authors. The coordinates of the point where normal grain growth turned abnormal was determined. These coordinates for testing steel are the reheating conditions TReh = 1060 °C, tReh = 1800 s at the diameter of austenite grain size dγ = 100 μm.

scholarly journals Mechanical and Processing Properties of Rice Grains

2020 ◽  
Vol 12 (2) ◽  
pp. 552 ◽  
Author(s):  
Weronika Kruszelnicka ◽  
Andrzej Marczuk ◽  
Robert Kasner ◽  
Patrycja Bałdowska-Witos ◽  
Katarzyna Piotrowska ◽  
...  
Keyword(s):  
Grain Size ◽  
Oryza Sativa ◽  
Negative Correlation ◽  
Oryza Sativa L ◽  
Strength Properties ◽  
Rice Grain ◽  
Static Compression ◽  
Positive Correlation ◽  
Rice Grains ◽  
Processing Properties

Strength properties of grains have a significant impact on the energy demand of grinding mills. This paper presents the results of tests of strength and energy needed the for destruction of rice grains. The research aim was to experimentally determine mechanical and processing properties of the rice grains. The research problem was formulated in the form of questions: (1) what force and energy are needed to induce a rupture of rice grain of the Oryza sativa L. of long-grain variety? (2) what is the relationship between grain size and strength parameters and the energy of grinding rice grain of the species Oryza sativa L. long-grain variety? In order to find the answer to the problems posed, a static compression test of rice grains was done. The results indicate that the average forces needed to crush rice grain are 174.99 kg m·s−2, and the average energy is 28.03 mJ. There was no statistically significant relationship between the grain volume calculated based on the volumetric mass density Vρ and the crushing energy, nor between the volume Vρ and other strength properties of rice grains. In the case of Vs, a low negative correlation between strength σmin and a low positive correlation between the power inducing the first crack were found for the grain size related volume. A low negative correlation between the grain thickness a3, stresses σmin and work WFmax was found as well as a low positive correlation between thickness a3 and the force inducing the first crack Fmin.

Rapid Synthesis of Nanostructural Intermetallics and their Bulk Properties

1996 ◽  
Vol 457 ◽  
Author(s):  
S. M. Pickard ◽  
A. K. Ghosh
Keyword(s):  
Grain Size ◽  
Physical Vapor Deposition ◽  
High Speed ◽  
Single Phase ◽  
Deposition Process ◽  
Indentation Hardness ◽  
Rotational Rate ◽  
Fine Grain ◽  
Compositional Variability ◽  
Nano Grains

ABSTRACTA rapid physical vapor deposition process (PVD) utilizing a high speed rotating substrate and small substrate-to-source spacing has been used to produce bulk sheet of Ti-Al alloys in the compositional range Ti-12% Al to Ti-75% Al1 at a rate of 1–3 μm/minute. Microstructural architectures produced by the method comprise of either fully homogenous phase mixtures of nano-grains, or nanolaminated material, depending on the substrate rotational rate, with lower rotational rate producing a layered microstructure. Defect populations within the as-deposited material are characterized by TEM and SEM, and hot pressing consolidation of the as-deposited material, which retains a grain size < 1000 nm, has been investigated. While indentation hardness of α2+γ(2 phase) alloys exceeded 7 GPa, brittle failure occurred in the elastic regime at nominally lower tensile stress than that for conventionally produced alloys containing Nb and Cr as solute elements. α2+γ alloys can exhibit tensile elongations of more than 100% at 850°C with retention of fine grain size. Elevated temperature failure occurs by the formation of voids in regions of compositional variability in the composite where single phase α2-Ti3Al structure was present.

scholarly journals Effect of Grain Size on the Microstructure and Strain Hardening Behavior of Solution Heat-Treated Low-C High-Mn Steel

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1489 ◽  
Author(s):  
Marek Opiela ◽  
Gabriela Fojt-Dymara ◽  
Adam Grajcar ◽  
Wojciech Borek
Keyword(s):  
Grain Size ◽  
Strain Hardening ◽  
Strengthening Mechanism ◽  
Strength Properties ◽  
Low Carbon ◽  
Premature Failure ◽  
Hardening Behavior ◽  
Heat Treated ◽  
Strain Hardening Behavior ◽  
Grain Diameter

The low-carbon high-Mn austenitic steel microalloyed with titanium was investigated in this work. The steel was solution heat-treated at different temperatures in a range from 900 to 1200 °C. The aim was to receive a different grain size before the static tensile test performed at room temperature. The samples of different grain sizes showed the different strain hardening behavior and resulting mechanical properties. The size of grain diameter below 19 μm was stable up to 1000 °C. Above this temperature, the very enhanced grain growth took place with the grain diameter higher than 220 μm at 1200 °C. This huge grain size at the highest temperature resulted in the premature failure of the sample showing the lowest strength properties at the same time. Correlations between the grain size, the major strengthening mechanism, and fracture behavior were addressed. The relationships were assessed based on microstructural investigations and fractography tests performed for the deformed samples. The best combination of strength and ductility was found for the samples treated at 1000–1100 °C.

Mg–TM (TM: Ti, Nb, V, Co, Mo or Ni) core–shell like nanostructures: synthesis, hydrogen storage performance and catalytic mechanism

2014 ◽  
Vol 2 (25) ◽  
pp. 9645-9655 ◽  
Author(s):  
Jie Cui ◽  
Jiangwen Liu ◽  
Hui Wang ◽  
Liuzhang Ouyang ◽  
Dalin Sun ◽  
...  
Keyword(s):  
Grain Size ◽  
Transition Metals ◽  
Hydrogen Storage ◽  
Catalytic Mechanism ◽  
Core Shell ◽  
Storage Performance ◽  
Nano Scale ◽  
Hydrogen Storage Performance

Magnesium coated by different transition metals (TM: Ti, Nb, V, Co, Mo, or Ni) with a grain size in the nano-scale formed a core (Mg)–shell (TM) like structure which can catalyse dehydrogenation.

Preparation of Nano-Scale Piece of Sericite by Using Mechanical Exfoliation Method and Ultrasonic Method

2012 ◽  
Vol 268-270 ◽  
pp. 184-188 ◽  
Author(s):  
Yu Liang ◽  
Hao Ding ◽  
Fen Chen
Keyword(s):  
Grain Size ◽  
Acid Treatment ◽  
Thermal Activation ◽  
Ultrasonic Method ◽  
Raw Material ◽  
Traditional Methods ◽  
Mechanical Exfoliation ◽  
Nano Scale

The structure of sericite is very stable, so it is hard to peel it directly using traditional methods. In this article, the sericite which was processed through thermal activation, acid treatment, Na-modification and CTAB intercalation was used as raw material to do the exfoliation. The mechanical exfoliation method and ultrasonic method were used respectively to exfoliate the modified sericite. The grain size of final product using mechanical exfoliation method reached 16.6nm and the grain size of final product using ultrasonic method reached 8.1nm. Alongside with the result of TEM images, the ultrasonic method is thought to be better.

Laser Growth of Thin Silicon Crystals in Patterned Structures

1980 ◽  
Vol 1 ◽  
Author(s):  
R. M. Fastow ◽  
H. J. Leamy ◽  
G. K. Celler ◽  
Y. H. Wong ◽  
C. J. Doherty
Keyword(s):  
Grain Size ◽  
Crystal Growth ◽  
Heat Flow ◽  
Single Crystals ◽  
Polycrystalline Silicon ◽  
Silicon Crystals ◽  
Patterned Structures ◽  
Amorphous Substrates ◽  
Thin Polycrystalline ◽  
Polycrystalline Silicon Films

ABSTRACTBeam processing can be applied to thin, polycrystalline silicon films on amorphous substrates to: a( increase grain size, b( produce single, isolated crystals, and c( to produce oriented single crystals. Specific methods for these tasks are outlined. Crystal growth and heat flow consideration appropriate to each are presented.

Anomalous fading in TL, OSL and TA – OSL signals of Durango apatite for various grain size fractions; from micro to nano scale

2018 ◽  
Vol 195 ◽  
pp. 216-224 ◽  
Author(s):  
G.S. Polymeris ◽  
I.K. Sfampa ◽  
M. Niora ◽  
E.C. Stefanaki ◽  
L. Malletzidou ◽  
...  
Keyword(s):  
Grain Size ◽  
Size Fractions ◽  
Nano Scale ◽  
Grain Size Fractions
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