scholarly journals The Effect of Different Thermal Treatment on the Allotropic fcc↔hcp Transformation and Compression Behavior of Polycrystalline Cobalt

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5775
Author(s):  
Michal Knapek ◽  
Peter Minárik ◽  
Patrik Dobroň ◽  
Jana Šmilauerová ◽  
Mayerling Martinez Celis ◽  
...  
Keyword(s):  
Grain Size ◽  
Yield Strength ◽  
Performance Optimization ◽  
Fracture Strain ◽  
Mechanical Performance ◽  
Effective Means ◽  
Basic Material ◽  
Phase Content ◽  
Compression Behavior ◽  
Fcc Phase

Pure polycrystalline cobalt is systematically thermally treated in order to assess the effect of the microstructure on the compression behavior. Isothermal annealing of the as-drawn material leads to recrystallization and grain growth dependent on the annealing temperature (600–1100 ∘C). Consequently, the yield strength decreases and the fracture strain increases as a function of rising grain size; the content of the residual fcc phase is ~6–11%. Subsequent thermal cycling around the transition temperature is applied to further modify the microstructure, especially in terms of the fcc phase content. With the increasing number of cycles, the grain size further increases and the fraction of the fcc phase significantly drops. At the same time, the values of both the yield strength and fracture strain somewhat decrease. An atypical decrease in the fracture strain as a function of grain size is explained in terms of decreasing fcc phase content; the stress-induced fcc→hcp transformation can accommodate a significant amount of plastic strain. Besides controlling basic material parameters (e.g., grain size and texture), adjusting the content of the fcc phase can thus provide an effective means of mechanical performance optimization with respect to particular applications.

scholarly journals Mechanical properties of boron nitride sheet with randomly distributed vacancy defects

2019 ◽  
Vol 8 (1) ◽  
pp. 210-217 ◽  
Author(s):  
Yingjing Liang ◽  
Hongfa Qin ◽  
Jianzhang Huang ◽  
Sha Huan ◽  
David Hui
Keyword(s):  
Mechanical Properties ◽  
Boron Nitride ◽  
Performance Optimization ◽  
Fracture Strain ◽  
Mechanical Performance ◽  
Hexagonal Boron Nitride ◽  
Stable Configuration ◽  
Vacancy Defects ◽  
And Performance ◽  
Dynamics Simulations

Abstract Defects and temperature effects on the mechanical properties of hexagonal boron nitride sheet (h-BN) containing randomly distributed defects are investigated by molecular dynamics simulations and the reasons of the results are discussed. Results show that defect deteriorate the mechanical performance of BNNS. The mechanical properties are reduced by increasing percentage of vacancy defects including fracture strength, fracture strain and Young’s modulus. Simulations also indicate that the mechanical properties decrease with the temperature increasing. Moreover, defects affect the stable configuration at high temperature. With the percentage of defect increases the nanostructures become more and more unstable. Positions of the defect influent the mechanical properties. The higher the temperature and the percentage of defect are, the stronger the position of the randomly distributed defect affects the mechanical properties. The study provides a theoretical basis for the preparation and performance optimization of BNNSs.

scholarly journals ODS EUROFER Steel Strengthened by Y-(Ce, Hf, La, Sc, and Zr) Complex Oxides

Metals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1148 ◽  
Author(s):  
Roman Husák ◽  
Hynek Hadraba ◽  
Zdeněk Chlup ◽  
Milan Heczko ◽  
Tomáš Kruml ◽  
...  
Keyword(s):  
Grain Size ◽  
Yield Strength ◽  
Complex Oxides ◽  
Oxide Dispersion Strengthened ◽  
Interparticle Spacing ◽  
Oxide Dispersion ◽  
Strengthening Effect ◽  
Dispersion Strengthening ◽  
Doping Element ◽  
Average Grain Size

Oxide dispersion-strengthened (ODS) materials contain homogeneous dispersions of temperature-stable nano-oxides serving as obstacles for dislocations and further pinning of grain boundaries. The strategy for dispersion strengthening based on complex oxides (Y-Hf, -Zr, -Ce, -La) was developed in order to refine oxide dispersion to enhance the dispersion strengthening effect. In this work, the strengthening of EUROFER steel by complex oxides based on Y and elements of the IIIB group (lanthanum, scandium) and IVB group (cerium, hafnium, zirconium) was explored. Interparticle spacing as a dispersoid characteristic appeared to be an important factor in controlling the dispersion strengthening contribution to the yield strength of ODS EUROFER steels. The dispersoid size and average grain size of ODS EUROFER steel were altered in the ranges of 5–13 nm and 0.6–1.7 µm, respectively. Using this strategy, the yield strength of the prepared alloys varied between 550 MPa and 950 MPa depending on the doping element.

Improvement of Strength of Mg-12Gd-3Y-0.5Zr Alloys Processed by Combination of ECAP and Extrusion

2011 ◽  
Vol 682 ◽  
pp. 211-216
Author(s):  
Rong Zhu ◽  
Jin Qiang Liu ◽  
Jing Tao Wang ◽  
Ping Huang ◽  
Yan Jun Wu ◽  
...  
Keyword(s):  
Grain Size ◽  
Yield Strength ◽  
Grain Boundary ◽  
Low Temperatures ◽  
Basal Slip ◽  
Extrusion Direction ◽  
Strengthening Mechanisms ◽  
Step Process ◽  
Angular Pressing ◽  
Peak Intensity

Equal channel angular pressing (ECAP) has been used to refine the grain size of Mg-12Gd-3Y-0.5Zr billet at about 400°C because it lacks sufficient ductility at low temperatures. However, <0001> peak intensity is oriented about 50º from the extrusion direction, which facilitates the basal slip, and decreases the yield strength. We have employed conventional extrusion at 300°C following ECAP to modify the texture in hard orientation. This two-step process makes use of two strengthening mechanisms a) grain boundary strengthening due to small grain size, and (b) texture strengthening due to grains in hard orientation. The samples processed by the two-step show the yield and ultimate strength to 283 and 308 MPa, respectively. Moreover, the activation of <c+a> slip and fine grains resulted from the ECAP helped to maintain a good ductility even after significant straining from conventional extrusion.

The effect of grain size on the yield strength of Ni3Al

1985 ◽  
Vol 33 (9) ◽  
pp. 1587-1591 ◽  
Author(s):  
E.M Schulson ◽  
T.P Weihs ◽  
D.V Viens ◽  
I Baker
Keyword(s):  
Grain Size ◽  
Yield Strength

Effects of Intensity of Alternating Electromagnetic Field on Microstructure and Property of ZL114A Aluminum Alloy Castings

2013 ◽  
Vol 278-280 ◽  
pp. 429-432
Author(s):  
Qing Song Yan ◽  
Yong Li ◽  
Gang Lu ◽  
Bai Ping Lu ◽  
Bo Wen Xiong ◽  
...  
Keyword(s):  
Grain Size ◽  
Electromagnetic Field ◽  
Aluminum Alloy ◽  
Mechanical Performance ◽  
Great Influence ◽  
Current Intensity ◽  
Alloy Castings

Through analyzing and testing the microstructure and property of ZL114A aluminum alloy castings under the condition of alternating electromagnetic field, the effects of the intensity of alternating electromagnetic field on the microstructure and property of ZL114A aluminum alloy castings are studied. The results showed the intensity of alternating electromagnetic field had a great influence on the microstructure and property of ZL114A aluminum alloy castings. With the increase of the intensity of alternating electromagnetic field, the grain size of ZL114A aluminum alloy was more and more small, under the 10A current intensity, the grain was the finest. Whereas, with the increase of the intensity of alternating electromagnetic field further, the grain is more and more big. Meanwhile, in a certain rang of current intensity, the mechanical performance of ZL114A aluminum alloy had been improved comprehensively, its tensile intensity was improved 10MPa and the elongation was increased by 30%.

Novel Microstructures in Microwave Sintered Silicon Nitride

1996 ◽  
Vol 430 ◽  
Author(s):  
M. E. Brito ◽  
K. Hirao ◽  
M. Toriyama ◽  
M. Hirota
Keyword(s):  
Grain Size ◽  
Silicon Nitride ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Mechanical Performance ◽  
Microwave Sintering ◽  
Preliminary Results ◽  
Nitride Ceramics ◽  
Positive Effect ◽  
Sintered Silicon

AbstractPreliminary results on microwave sintering of seeded silicon nitride show that a well defined bi-modal grain size distribution is attainable in Si3N4-Y2O3-Al2O 3-MgO sintered bodies by microwave sintering at 28 GHz of materials seeded with ß-Si3N4 particles (2 vol. %). A positive effect on the mechanical performance is anticipated for these microstructurally controlled silicon nitride ceramics

Microstructure and Mechanical Performance of AZ31-1.7 Wt.% Si Alloy Processed by Cyclic Channel Die Compression

2010 ◽  
Vol 667-669 ◽  
pp. 457-461
Author(s):  
Wei Guo ◽  
Qu Dong Wang ◽  
Man Ping Liu ◽  
Tao Peng ◽  
Xin Tao Liu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Tensile Strength ◽  
Mechanical Performance ◽  
Chinese Script ◽  
Cast State ◽  
Microstructure And Mechanical Properties ◽  
Mean Grain Size ◽  
The Matrix ◽  
The Mean

Cyclic channel die compression (CCDC) of AZ31-1.7 wt.% Si alloy was performed up to 5 passes at 623 K in order to investigate the microstructure and mechanical properties of compressed alloys. The results show that multi-pass CCDC is very effective to refine the matrix grain and Mg2Si phases. After the alloy is processed for 5 passes, the mean grain size decreases from 300 μm of as-cast to 8 μm. Both dendritic and Chinese script type Mg2Si phases break into small polygonal pieces and distribute uniformly in the matrix. The tensile strength increases prominently from 118 MPa to 216 MPa, whereas the hardness of alloy deformed 5 passes only increase by 8.4% compared with as-cast state.

Paradox of Strength and Ductility in Metals Processed Bysevere Plastic Deformation

2002 ◽  
Vol 17 (1) ◽  
pp. 5-8 ◽  
Author(s):  
R. Z. Valiev ◽  
I. V. Alexandrov ◽  
Y. T. Zhu ◽  
T. C. Lowe
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Grain Size ◽  
Yield Strength ◽  
Mechanical Behavior ◽  
High Strength ◽  
High Ductility ◽  
Elongation To Failure ◽  
Failure Ductility ◽  
Strength And Ductility

It is well known that plastic deformation induced by conventional forming methodssuch as rolling, drawing or extrusion can significantly increase the strength of metalsHowever, this increase is usually accompanied by a loss of ductility. For example, Fig.1 shows that with increasing plastic deformation, the yield strength of Cu and Almonotonically increases while their elongation to failure (ductility) decreases. Thesame trend is also true for other metals and alloys. Here we report an extraordinarycombination of high strength and high ductility produced in metals subject to severeplastic deformation (SPD). We believe that this unusual mechanical behavior is causedby the unique nanostructures generated by SPD processing. The combination ofultrafine grain size and high-density dislocations appears to enable deformation by newmechanisms. This work demonstrates the possibility of tailoring the microstructures ofmetals and alloys by SPD to obtain both high strength and high ductility. Materialswith such desirable mechanical properties are very attractive for advanced structuralapplications.

A work-hardening model of the lower yield strength of discontinuously yielding alloys: Ni3Al and mild steel

1989 ◽  
Vol 4 (3) ◽  
pp. 470-472 ◽  
Author(s):  
E. M. Schulson
Keyword(s):  
Grain Size ◽  
Yield Strength ◽  
Mild Steel ◽  
Work Hardening ◽  
Lower Yield ◽  
Hardening Model ◽  
Lower Yield Strength ◽  
Work Hardening Model ◽  
Lüders Bands

The lower yield strengths of Ni3Al and mild steel and their respective relationships to (grain size)−0.8 and (grain size)−0.5 are explained in terms of work hardening within Lüders bands.

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