Microstructure Evolution and Deformation Mechanisms of Harmonic Structure Designed Materials

2016 ◽  
Vol 879 ◽  
pp. 145-150
Author(s):  
Kei Ameyama ◽  
Sanjay Kumar Vajpai ◽  
Mie Ota
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Powder Metallurgy ◽  
Early Stage ◽  
High Strength ◽  
Plastic Instability ◽  
Structure Design ◽  
Harmonic Structure ◽  
Homogeneous Microstructure ◽  
Macro Scale

This paper presents the novel microstructure design, called Harmonic Structure, which gives structural metallic materials outstanding mechanical properties through an innovative powder metallurgy process. Homogeneous and ultra-fine grain (UFG) structure enables the materials high strength. However, such a “Homo-“ and “UFG” microstructure does not, usually, satisfy the need to be both strong and ductile, due to the plastic instability in the early stage of the deformation. As opposed to such a “Homo-and UFG“ microstructure, “Harmonic Structure” has a heterogeneous microstructure consisting of bimodal grain size together with a controlled and specific topological distribution of fine and coarse grains. In other words, the harmonic structure is heterogeneous on micro-but homogeneous on macro-scales. In the present work, the harmonic structure design has been applied to pure metals and alloys via a powder metallurgy route consisting of controlled severe plastic deformation of the corresponding powders by mechanical milling or high pressure gas milling, and subsequent consolidation by SPS. At a macro-scale, the harmonic structure materials exhibited superior combination of strength and ductility as compared to their homogeneous microstructure counterparts. This behavior was essentially related to the ability of the harmonic structure to promote the uniform distribution of strain during plastic deformation, leading to improved mechanical properties by avoiding or delaying localized plastic instability.

High Temperature Mechanical Properties of Harmonic Structure Designed SUS304L Austenitic Stainless Steel

2016 ◽  
Vol 879 ◽  
pp. 2507-2511 ◽  
Author(s):  
Masashi Nakatani ◽  
Yuya Fujiki ◽  
Mie Ota ◽  
Sanjay Kumar Vajpai ◽  
Kei Ameyama
Keyword(s):  
Stainless Steel ◽  
High Temperature ◽  
Austenitic Stainless Steel ◽  
Elevated Temperatures ◽  
Early Stage ◽  
Tensile Tests ◽  
Structure Design ◽  
Harmonic Structure ◽  
Homogeneous Microstructure ◽  
Macro Scale

Through many years, conventional material developments have emphasized on microstructural refinement and homogeneity. However, "nanoand Homogeneous "microstructures do not, usually, satisfy the need to be both strong and ductile, due to the plastic instability in the early stage of the deformation. As opposed to such a “nanoand homo-“microstructure design, we have proposed “Harmonic Structure” design. The harmonic structure has a heterogeneous microstructure consisting of bimodal grain size together with a controlled and specific topological distribution of fine and coarse grains. In other words, the harmonic structure is heterogeneous on micro-but homogeneous on macro-scales. In the present work, the harmonic structure design has been applied to SUS304L austenitic stainless steel via a ball milling process and a large size (50 mm in diameter) SPS sintering process. At a macro-scale, the harmonic structure SUS304Lcompacts exhibited significantly better combination of strength and ductility, under quasi-static tensile loadings, as compared to their homogeneous microstructure counterparts. High temperature tensile tests revealed that they also indicated high strength at elevated temperatures.

Harmonic Structure Design of Co-Cr-Mo Alloy with Outstanding Mechanical Properties

2014 ◽  
Vol 939 ◽  
pp. 60-67 ◽  
Author(s):  
Choncharoen Sawangrat ◽  
Osamu Yamaguchi ◽  
Sanjay Kumar Vajpai ◽  
Kei Ameyama
Keyword(s):  
Mechanical Properties ◽  
Mechanical Milling ◽  
Three Dimensional ◽  
High Strength ◽  
Surface Region ◽  
Structure Design ◽  
Coarse Grained ◽  
Harmonic Structure ◽  
Fine Grained ◽  
Plasma Sintering

Co-Cr-Mo alloy powders were subjected to controlled mechanical milling at room temperature under Ar atmosphere to fabricate bimodal microstructure in the MM powders, having nanosized grains in the surface region and micron-sized coarse grains in the center of the milled powders. Subsequently, the MM powder was compacted by spark-plasma sintering (SPS) process. The sintered compacts indicated two structure areas: (i) ultra-fine grained (UFG) regions, called shell, and (ii) the coarse grained regions called core. The shell and the core correspond to the surface and center of the MM powders, respectively. The shell regions established a continuous three dimensional network of high strength ultra-fine grained regions, which surrounded the discrete coarse grained ductile regions. Such a microstructure is referred as Harmonic Structure. The sintered Co-Cr-Mo alloy compacts exhibited outstanding mechanical properties. The yield strength increased from 605 to 635 MPa, and ultimate tensile strength increased from 1201 to 1283 MPa. Moreover, the elongation was maintained more or less same as that of coarse grained compacts. Therefore, the harmonic structure design leads to the new generation microstructure of Co-Cr-Mo alloy, which demonstrates outstanding mechanical properties, i.e. superior strength and excellent ductility as compared to conventional materials. Keywords: mechanical milling, Co-Cr-Mo alloys, mechanical properties, harmonic structure.

Improving Mechanical Properties of Co-Cr-W Alloys by Powder Metallurgy

2017 ◽  
Vol 890 ◽  
pp. 348-351
Author(s):  
Choncharoen Sawangrat ◽  
Komgrit Leksakul
Keyword(s):  
Mechanical Properties ◽  
Powder Metallurgy ◽  
Total Elongation ◽  
Structure Design ◽  
Coarse Grained ◽  
Harmonic Structure ◽  
Fine Grained ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Commercial Applications

This study focuses on improving the mechanical properties of Co-Cr-W alloys by applying Harmonic Structure Design – bimodal grain size distribution with an interconnected framework of ultra-fine-grained (UFG) regions, called the “shell region”, surrounding isolated coarse-grained (CG) regions. Harmonic structure Co-Cr specimens were successfully fabricated by Powder Metallurgy (PM) that consisted of controlled mechanical milling and spark plasma sintering. The sintered compacts revealed an outstanding combination of strength and total elongation. Moreover, the sintering dwell time significantly improved densification and led to large total elongation. PM improved the mechanical properties of Co-Cr-W alloys and offered an attractive approach to fabricate harmonic structures for commercial applications.

Development Of High-Strength Aluminum-Based Alloys By Synthesis Of New Multicomponent Quasicrystals

1998 ◽  
Vol 553 ◽  
Author(s):  
A. Inoue ◽  
H. M. Kimura
Keyword(s):  
Mechanical Properties ◽  
Powder Metallurgy ◽  
Rapid Solidification ◽  
Future Development ◽  
High Strength ◽  
Supercooled Liquid ◽  
Engineering Properties ◽  
Atomic Configuration ◽  
Lanthanide Metal ◽  
Bulk Alloys

AbstractBy the control of composition, clustered atomic configuration and stability of the supercooled liquid in the rapid solidification and powder metallurgy processes, high-strength Al-based bulk alloys containing nanoscale nonperiodic phases were produced in AI-Ln-LTM, AI-ETM-LTM and Al-(V, Cr, Mn)-LTM (Ln=lanthanide metal, LTM=VII and VIII group metals, ETM=IV to VI group metals) alloys containing high Al contents of 92 to 95 at%. The nonperiodic phases are composed of amorphous or icosahedral (I) phase. In particular, the Al-based bulk alloys consisting of nanoscale I particles surrounded by Al phase exhibit much better mechanical properties as compared with commercial Al base alloys. The success of producing the Al-based alloys with good engineering properties by use of I phase is important for future development of I-based alloys as practical materials.

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.

Characterization and Properties of Copper-Silica Sand Nanoparticle Composites

2011 ◽  
Vol 319-320 ◽  
pp. 95-105 ◽  
Author(s):  
Tahir Ahmad ◽  
Othman Mamat
Keyword(s):  
Mechanical Properties ◽  
Electrical Conductivity ◽  
Plastic Deformation ◽  
Powder Metallurgy ◽  
Silica Sand ◽  
Prealloyed Powder ◽  
Powder Metallurgy Process ◽  
Rearrangement Mechanism ◽  
Nanoparticle Composites ◽  
Metallurgy Process

Copper-based microcomposites fabricated by powder metallurgy with subsequent plastic deformation have received increasing attention over recent years. These microcomposites possess good electrical conductivity in combination with high mechanical properties. The present study aims to explore potential technical merits in developing a prealloyed powder metallurgy copper based composites with silica sand nanoparticles reinforcement. Relevant mechanical properties and electrical conductivity improvements are the main targets. A copper based composite with 5, 10, 15 and 20 wt.% of silica sand nanoparticles were developed through the powder metallurgy process. It was observed that by addition of silica sand nanoparticles with 20% increased the hardness up to 143HV. Optimum electrical conductivity of the composites was achieved in the 15 wt.% silica sand nanoparticles. Advanced particle rearrangement mechanism due to homogeneous and fine distribution of silica sand nanoparticles into pore sites of the composites was also observed. The silica sand nanoparticles composites properties that are much more surface-related seen to be improved convincingly compared with the bulk controlled.

Mechanical Properties of High-Manganese Austenitic TWIP-Type Steel

2014 ◽  
Vol 783-786 ◽  
pp. 27-32 ◽  
Author(s):  
Leszek Adam Dobrzański ◽  
Wojciech Borek ◽  
Janusz Mazurkiewicz
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
High Strength ◽  
Deformation Energy ◽  
Mechanical Twinning ◽  
Austenitic Steels ◽  
Manganese Steel ◽  
Cold Plastic Deformation ◽  
High Plasticity ◽  
High Manganese

Taking into consideration increased quantity of accessories used in modern cars, decreasing car’s weight can be achieved solely by optimization of sections of sheets used for bearing and reinforcing elements as well as for body panelling parts of a car. Application of sheets with lower thickness requires using sheets with higher mechanical properties, however keeping adequate formability. The goal of structural elements such as frontal frame side members, bumpers and the others is to take over the energy of an impact. Therefore, steels that are used for these parts should be characterized by high value of UTS and UEl, proving the ability of energy absorption. Among the wide variety of recently developed steels, high-manganese austenitic steels with low stacking faulty energy are particularly promising, especially when mechanical twinning occurs. Beneficial combination of high strength and ductile properties of these steels depends on structural processes taking place during cold plastic deformation, which are a derivative of SFE of austenite, dependent, in turn on the chemical composition of steel and deformation temperature. High-manganese austenitic steels in effect of application of proper heat treatment or thermo-mechanical treatment can be characterized by different structure assuring the advantageous connection of strength and plasticity properties. Proper determinant of these properties can be plastic deformation energy supply determined by integral over surface of cold plastic deformation curve. Obtaining of high strength properties with retaining the high plasticity has significant influence for the development of high-manganese steel groups and their significance for the development of materials engineering.

Influence of Severe Plastic Deformation on Mechanical Properties of an AA5024 Alloy

2016 ◽  
Vol 879 ◽  
pp. 1317-1322 ◽  
Author(s):  
Anna Mogucheva ◽  
Diana Yuzbekova ◽  
Tatiana Lebedkina ◽  
Mikhail Lebyodkin ◽  
Rustam Kaibyshev
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Severe Plastic Deformation ◽  
High Strength ◽  
Coarse Grained ◽  
Type B ◽  
Angular Pressing ◽  
Ultrafine Grained ◽  
Elongation To Failure ◽  
Dislocation Strengthening

The paper reports on the effect of severe plastic deformation on mechanical properties of an Al-4.57Mg-0.35Mn-0.2Sc-0.09Zr (in wt. pct.) alloy processed by equal channel angular pressing followed by cold rolling (CR). The sheets of the 5024 alloy with coarse grained (CG) structure exhibited a yield stress (YS) near 410 MPa and an ultimate tensile strength (UTS) of 480 MPa, while the YS and UTS of this material with ultrafine-grained (UFG) structure increased to 530 and 560 MPa, respectively. On the other hand, the elongation to failure decreased by a factor of 2 and 4 after CR and CR following ECAP, respectively. It was shown that dislocation strengthening attributed to extensive CR plays a major role in achieving high strength of this alloy. Besides these macroscopic characteristics, jerky flow caused by the Portevin-Le Chatelier (PLC) instability of plastic deformation was examined. The formation of UFG structure results in a transition from mixed type A+B to pure type B PLC serrations. No such effect on the serrations type was observed after CR.

scholarly journals Comparative analysis of characteristics of stainless steel cellular material prepared through powder metallurgy using accicular and crushed urea as spaceholder

2019 ◽  
Vol 16 (2) ◽  
pp. 183-188
Author(s):  
Shailendra Joshi
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Powder Metallurgy ◽  
High Strength ◽  
Metallic Foam ◽  
Space Holder ◽  
Excellent Mechanical Property ◽  
Circular Holes ◽  
Steel Foam ◽  
Damping Capability

Stainless steel has an excellent mechanical property as well as high corrosion resistance. Stainless steel foams, therefore, seemed like an attractive material for impact energy absorption applications where damping capability is required such as in vehicles and buildings. Also when stainless steel foam is produced as stainless steel foam, the material density will be reduced thus the resulting foam will be a combination of light weight and high strength that can also be used in high strength applications. In our analysis, we tried to produce stainless steel foam through powder metallurgy in order to control mechanical properties in a better manner compared to the casting method. Also, we try to compare the pore morphology in foams on changing the space holder from accicular urea to crushed urea using FE-SEM. The properties of stainless steel foam, to a large extent, are found to depend on the arrangement of the pores which is decided by the space holder utilized during its synthesis using powder metallurgy route. The stainless steel obtained using acicular carbamide as space holder is found to possess acicular or irregular pores whereas those produced with crushed urea as space holder possesses nearly circular holes. Also, the previous foams are found to have better mechanical properties contributing towards more useful metallic foam.

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