scholarly journals Mechanism of Gradient Strengthening Layer Formation Based on Microstructure and Microhardness of Inconel 718 Grinding Surface

2021 ◽  
Author(s):  
Zhigang Dong ◽  
Nianwei Xu ◽  
Yuan Zhang ◽  
Lu Han ◽  
Renke Kang ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Refinement ◽  
Inconel 718 ◽  
Strengthening Mechanism ◽  
High Density ◽  
Microstructure Observation ◽  
Dislocation Strengthening ◽  
The Difference ◽  
Dislocation Layer ◽  
Grain Boundary Strengthening

Abstract Gradient strengthening layer will emerge on the grinding surface of Inconel 718 due to the difference of microstructure. The surface microstructure and microhardness are not independent of each other, and the microhardness is the embodiment of the microstructure evolution in the strength aspect. In this paper, the microstructure observation, microhardness experiments and strengthening theory were combined to analyze. The experimental results show that the grinding surface consists of grain refinement layer and high-density dislocation layer. The grain refinement layer is constituted of equiaxed nano-grains and elongated grains, in which grain boundary strengthening occurred leading to an increase in microhardness. Dislocation strengthening occurred in the high-density dislocation layer, in which the increment of dislocation density is approximately 3.54 × 109 mm− 2 compared with inner matrix. Microhardness of high-density dislocation region reaches the maximum (438.6 ± 11.1 HV0.01) because of the dislocation strengthening. The variation of microhardness is discussed from two strengthening mechanisms of grain boundary strengthening and dislocation strengthening, and the strengthening mechanism in the different regions of grinding surface is revealed. The calculated microhardness increments through these mechanisms in the refined-grain region and the high-density dislocation region are basically consistent with the measured values.

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

Materials ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 339 ◽  
Author(s):  
Yong Wang ◽  
Jinguo Wang ◽  
Haohao Zou ◽  
Yutong Wang ◽  
Xu Ran
Keyword(s):  
Electrical Conductivity ◽  
Grain Size ◽  
Yield Strength ◽  
Grain Boundary ◽  
High Strength ◽  
Strengthening Mechanism ◽  
Copper Matrix ◽  
Dispersion Strengthening ◽  
Annealed Copper ◽  
Grain Boundary Strengthening

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.

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

Nanomaterials ◽  
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.

Thermal stability and grain boundary strengthening in ultrafine-grained CoCrFeNi high entropy alloy composite

2017 ◽  
Vol 134 ◽  
pp. 426-433 ◽  
Author(s):  
Praveen Sathiyamoorthi ◽  
Joysurya Basu ◽  
Sanjay Kashyap ◽  
K.G. Pradeep ◽  
Ravi Sankar Kottada
Keyword(s):  
Thermal Stability ◽  
Grain Boundary ◽  
High Entropy Alloy ◽  
Alloy Composite ◽  
High Entropy ◽  
Ultrafine Grained ◽  
Grain Boundary Strengthening

scholarly journals Variation of class I HLA antigen expression among platelet density cohorts: a possible index of platelet age?

Blood ◽  
1988 ◽  
Vol 71 (2) ◽  
pp. 516-519
Author(s):  
J Pereira ◽  
C Cretney ◽  
RH Aster
Keyword(s):  
Hla Antigens ◽  
Antigen Expression ◽  
High Density ◽  
Class I ◽  
Surface Markers ◽  
Low Density ◽  
Hla Antigen ◽  
The Difference ◽  
Hla Molecules

Platelet alloantigens and other surface markers were studied in platelet cohorts of different mean density, using monoclonal and polyclonal probes. High density (HD) platelets expressed 12% more P1A1 molecules (46,942) than low density (LD) platelets (41,892). However, LD platelets carried 42% more HLA-A2 molecules (6,267 +/- 184) than HD platelets (4,406 +/- 232) (P less than .01) and 55% more class I HLA antigens (17,034 +/- 2,062 v 11,007 +/- 2,190) (P = .05). The platelet subpopulations did not differ in their content of glycoprotein (GP)IIb/IIIa complex or Baka antigen. The difference in expression of class I HLA antigens on HD and LD platelets is consistent with two possibilities: either class I HLA molecules are acquired from plasma or they are released into plasma as platelets age in circulation. Accordingly, class I HLA molecules may provide a useful marker of platelet age.

Grain boundary strengthening in austenitic nitrogen steels

1999 ◽  
Vol 271 (1-2) ◽  
pp. 14-21 ◽  
Author(s):  
V.G Gavriljuk ◽  
H Berns ◽  
C Escher ◽  
N.I Glavatskaya ◽  
A Sozinov ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Nitrogen Steels ◽  
Grain Boundary Strengthening
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