Microstructure and Enhanced Properties of Copper-Vanadium Nanocomposites Obtained by Powder Metallurgy

Cu-2.4 wt.%V nanocomposite has been prepared by mechanical alloy and vacuum hot-pressed sintering technology. The composites were sintered at 800 °C, 850 °C, 900 °C, and 950 °C respectively. The microstructure and properties of composites were investigated. The results show that the Cu-2.4 wt.%V composite presents high strength and high electrical conductivity. The composite sintered at 900 °C has a microhardness of 205 HV, a yield strength of 404.41 MPa, and an electrical conductivity of 79.5% International Annealed Copper Standard (IACS); the microhardness and yield strength reduce gradually with the increasing consolidation temperature, which is mainly due to the growth of copper grain size. After sintering, copper grain size and V nanoparticle both maintain in nanoscale; the strengthening mechanism is related to grain boundary strengthening and dispersion strengthening, while the grain boundary strengthening mechanism plays the most important role. This study indicates that the addition of small amounts of V element could enhance the copper matrix markedly with the little sacrifice of electrical conductivity.

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Design and Synthesis of C-O Grain Boundary Strengthening of Al Composites

Nanomaterials ◽

10.3390/nano10030438 ◽

2020 ◽

Vol 10 (3) ◽

pp. 438

Author(s):

Jianian Hu ◽

Jian Zhang ◽

Guoqiang Luo ◽

Yi Sun ◽

Qiang Shen ◽

...

Keyword(s):

Tensile Strength ◽

Ultimate Tensile Strength ◽

Yield Strength ◽

Grain Boundary ◽

Pure Aluminum ◽

Polyvinyl Butyral ◽

Strengthening Mechanism ◽

Vertical Tube ◽

Al Matrix ◽

Grain Boundary Strengthening

This research presents an approach for C-O grain boundary strengthening of Al composites that used an in situ method to synthesize a C-O shell on Al powder particles in a vertical tube furnace. The C-O reinforced Al matrix composites (C-O/Al composites) were fabricated by a new powder metallurgy (PM) method associated with the hot pressing technique. The data indicates that Al4C3 was distributed within the Al matrix and an O-Al solution was distributed in the grain boundaries in the strengthened structure. The formation mechanism of this structure was explained by a combination of TEM observations and molecular dynamic simulation results. The yield strength and ultimate tensile strength of the C-O/Al composites, modified by 3 wt.% polyvinyl butyral, reached 232.2 MPa and 304.82 MPa, respectively; compared to the yield strength and ultimate tensile strength of the pure aluminum processed under the same conditions, there was an increase of 124% and 99.3%, respectively. These results indicate the excellent properties of the C-O/Al-strengthened structure. In addition, the strengthening mechanism was explained by the Hall–Petch strengthening, dislocation strengthening, and solid solution strengthening mechanisms, which represented contributions of nearly 44.9%, 15.9%, and 16.6% to the total increased strength, respectively. The remaining increment was attributed to the coupled strengthening of the C and O, which contributed 20.6% to the total increase.

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Development of Micro-Alloying Ultra-Fine Grain High Strength Steel Produced by EAF-TSCR

Materials Science Forum ◽

10.4028/www.scientific.net/msf.697-698.474 ◽

2011 ◽

Vol 697-698 ◽

pp. 474-478

Author(s):

Ji Xiang Gao ◽

Xin Ping Mao ◽

L.J. Li

Keyword(s):

Grain Size ◽

Yield Strength ◽

Continuous Casting ◽

High Strength Steel ◽

Raw Materials ◽

High Strength ◽

Strengthening Mechanism ◽

Fine Grain ◽

Ferrite Grain Size

Based on the characteristics of raw materials in EAF-TSCR, the composition of VN micro-alloyed was designed, the processes of the steelmaking, continuous casting, soaking, rolling, cooling were controlled, and at last the VN Micro-alloying high strength steel with ultra-fine grain was developed. The ferrite grain size of the steel reaches 3.0 to 4.0 microns, and the yield strength of which reaches 550MPa. Besides, the steel processes good toughness, cold formability and weldability. In the end, the strengthening mechanism of the ultra-fine steel was discussed.

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

Metals ◽

10.3390/met9111148 ◽

2019 ◽

Vol 9 (11) ◽

pp. 1148 ◽

Cited By ~ 2

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.

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

Materials Science Forum ◽

10.4028/www.scientific.net/msf.682.211 ◽

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.

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Fabrication of Cu-Al2O3 Composites by Simplified Internal Oxidation Process

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.148-149.416 ◽

2010 ◽

Vol 148-149 ◽

pp. 416-419

Author(s):

Bao Hong Tian ◽

Cheng Dong Xia ◽

Shu Guo Jia

Keyword(s):

Electrical Conductivity ◽

Tensile Strength ◽

Internal Oxidation ◽

Oxidation Process ◽

Hot Extrusion ◽

Softening Temperature ◽

Copper Matrix ◽

Dispersion Strengthening ◽

Powder Metallurgical Process ◽

Thermal Stability Of

Cu-Al2O3 composites were prepared by a new simplified internal oxidation process integrating with powder metallurgical process, and then the hot extrusion and the cold rolling processes were carried out. The microstructure, electrical conductivity, hardness, tensile strength and thermal stability of the composites were investigated. The results show that Cu-Al2O3 composites were fabricated successfully by the simplified process in which internal oxidation completed during the sintering. There are a mass of fine Al2O3 particles in size varying from 5 nm to 20nm dispersed in copper matrix after sintering 950 for 4h. After sintered at 950 for 4h and extruded at 950 followed with the cold deforming of 80%, the electrical conductivity, hardness, tensile strength and softening temperature of composite reach 81％IACS, 137HV, 561MPa and 850 respectively. It is considered that the dispersion strengthening and strain hardening have greatly contribution to the Cu-Al2O3 composites fabricated with the simplified process.

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Dislocation versus grain boundary strengthening in SPD processed metals: Non-causal relation between grain size and strength of deformed polycrystals

Materials Science and Engineering A ◽

10.1016/j.msea.2017.08.069 ◽

2017 ◽

Vol 705 ◽

pp. 42-45 ◽

Cited By ~ 28

Author(s):

M.J. Starink

Keyword(s):

Grain Size ◽

Grain Boundary ◽

Causal Relation ◽

Grain Boundary Strengthening

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Paradox of Strength and Ductility in Metals Processed Bysevere Plastic Deformation

Journal of Materials Research ◽

10.1557/jmr.2002.0002 ◽

2002 ◽

Vol 17 (1) ◽

pp. 5-8 ◽

Cited By ~ 858

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.

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Effect of enhanced weld cooling on the mechanical properties of a structural steel with a yield strength of 700 MPa

SN Applied Sciences ◽

10.1007/s42452-020-03695-x ◽

2020 ◽

Vol 2 (11) ◽

Author(s):

Juhani Laitila ◽

Lassi Keränen ◽

Jari Larkiola

Keyword(s):

Mechanical Properties ◽

Grain Size ◽

Fatigue Strength ◽

Impact Toughness ◽

Yield Strength ◽

Uniform Elongation ◽

High Strength ◽

Low Alloy Steel ◽

External Cooling ◽

Welding Processes

AbstractIn this study, we present the effect of enhanced cooling on the mechanical properties of a high-strength low-alloy steel (having a yield strength of 700 MPa) following a single-pass weld process. The properties evaluated in this study include uniform elongation, impact toughness, yield, tensile and fatigue strengths alongside the cooling time of the weld. With the steel used in this study, the enhanced cooling resulted in a weld joint characterized with excellent cross-weld uniform elongation, yield and fatigue strength. The intensified cooling reduced the time it takes for the weld to reach 100 °C by around 190 s. Not only the fusion line of the weld was less pronounced, but also the grain size of the CGHAZ was greatly refined as a result of the enhanced cooling. The results indicate that combining external cooling to the welding processes can be beneficial for the studied high-strength steel.

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