The Effect of BN Reinforcement on the Mechanical Properties of Nanostructured Al2O3 Ceramics

2020 ◽  
Vol 20 (7) ◽  
pp. 4353-4357 ◽  
Author(s):  
Seong-Eun Kim ◽  
Woo-Jin Cho ◽  
Jin-Kook Yoon ◽  
In-Jin Shon
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Grain Size ◽  
Transition Temperature ◽  
Composite Materials ◽  
Pulsed Current ◽  
Nanostructured Composite ◽  
Reinforcing Agent ◽  
Rapid Sintering ◽  
Sintering Method

In spite of many attractive properties, the low fracture toughness of Al2O3 ceramic below ductilebrittle transition temperature limits its wide application in industry. One of the most obvious methods to improve the fracture toughness has been to add reinforcing compounds to fabricate nanostructured composite materials. In this respect, BN was evaluated as the reinforcing agent of Al2O3 ceramics using pulsed current activated sintering (PCAS). Highly dense alumina-BN composites with a relative density of up to 100% were achieved within short periods (2 min) by PCAS under a 80 MPa pressure. The rapid sintering method allowed the retention of the nanostructure by inhibiting the grain growth. The grain size of alumina was reduced remarkably by the addition of BN. The addition of BN to Al2O3 ceramic simultaneously improved the hardness and fracture toughness of alumina-BN composite.

Rapid Sintering of Nanostructured WC-Graphene Composites and Their Mechanical Properties

2020 ◽  
Vol 20 (7) ◽  
pp. 4436-4439
Author(s):  
Seong-Eun Kim ◽  
Jin-Kook Yoon ◽  
In-Jin Shon
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
High Frequency ◽  
Second Phase ◽  
Ductile Brittle Transition Temperature ◽  
Reinforcing Agent ◽  
Current Concern ◽  
Rapid Sintering ◽  
Sintering Method ◽  
High Frequency Induction

The current concern about WC focuses on its low fracture toughness below the ductile-brittle transition temperature despite its many attractive properties. To improve its mechanical properties, the approach generally utilized has been the addition of a second phase to form composites and to make nanostructured materials. In this paper, graphene was evaluated as the reinforcing agent in WC ceramics using a novel sintering method (high-frequency induction heated sintering method). Highly dense nanostructured WC and WC-graphene composites were obtained within two min at 1550 °C. The effect of graphene on the grain size and the mechanical properties (hardness and fracture toughness) of WC-graphene composites was evaluated.

Mechanical Properties and Consolidation of WC-8wt.%Ni Hard Materials by HFIHS and PCAS

2007 ◽  
Vol 124-126 ◽  
pp. 1153-1156 ◽  
Author(s):  
In Kyoon Jeong ◽  
Hwan Cheol Kim ◽  
Jung Mann Doh ◽  
Jin Kook Yoon ◽  
In Yong Ko ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Particle Size ◽  
Grain Size ◽  
High Frequency ◽  
Sintering Behavior ◽  
Pulsed Current ◽  
Hard Materials ◽  
Short Time ◽  
High Frequency Induction

Two methods, High-Frequency Induction-Heated Sintering (HFIHS) and Pulsed Current Activated Sintering (PCAS), were utilized to consolidate WC-8wt.%Ni hard materials. The demonstrated advantages of these processes are rapid densification to near theoretical density in a relatively short time and with insignificant change in grain size. The hardness, fracture toughness, and the relative density of the dense WC–8Ni composites produced by HFIHS and PCAS were investigated. And the effect of variation in particle size of WC powder on the sintering behavior and mechanical properties were investigated.

FABRICATION OF NANOSTRUCTURED WC-BASED HARD MATERIALS WITH DIFFERENT CONTENTS OF Co BY HIGH FREQUENCY INDUCTION HEATED SINTERING

2010 ◽  
Vol 17 (02) ◽  
pp. 251-255
Author(s):  
DUCK-SOO KANG ◽  
KEE-DO WOO ◽  
EUI-PYO KWON ◽  
SANG-HYUK KIM ◽  
MIN-SEOK MOON ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
High Frequency ◽  
Cutting Tool ◽  
Hard Material ◽  
Hard Materials ◽  
Sintering Time ◽  
Rapid Sintering ◽  
Sintering Method ◽  
High Frequency Induction

Hard materials, in particular tungsten carbide ( WC ) hard material has been used in many industries as cutting tool and abrasive materials. For improving toughness, binders are added into carbide materials. The effect of Co as binder on the mechanical properties in the nanosized WC was discussed. The hardness and fracture toughness were also investigated using 30 kgf load Vickers indenter. The nanosized WC-8 , 10 and 12 vol.% Co composites were successfully fabricated without grain growth by high frequency induction heated sintering (HFIHS), which is the rapid sintering method, due to short sintering time 1140°C. The nanosized WC–Co composites fabricated by HFIHS have better mechanical properties than WC–Co composite fabricated by commercial sintering.

Effect of Microcast-X Fine Grain Casting on the Microstructure and Mechanical Properties of K492M Alloy at 760°C

2016 ◽  
Vol 849 ◽  
pp. 549-556
Author(s):  
Pin Pin Hu ◽  
Qi Dong Gai ◽  
Qing Li ◽  
Xin Tang
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Grain Size ◽  
Rupture Life ◽  
Stress Rupture ◽  
Casting Alloy ◽  
Stress Rupture Life ◽  
Casting Technique ◽  
Conventional Casting ◽  
Fine Grain

The effect of Microcast-X fine grain casting on the microstructure and mechnical property K492M alloy at 760°C of was investigated. The results indicated that Microcast-X fine grain casting decreased grain size and dendrite space of γ′ phase and γ/γ′ eutectic. In addition, the element segregation decreased significantly compared to conventional casting technique. Also, the size and distribution of MC carbide were improved. By Microcast-X fine grain casting, the tensile strength increased from 934MPa of conventional casting alloy to 1089MPa and the elongation increased from 1.9% to 5.7%. In addition, the stress-rupture life increased from 28.8h of conventional casting alloy to 72.5h. And the fracture mechanism for the alloys by Microcast-X fine grain casting is trans-granular fracture toughness.

Thermal Conductivity of Si₃N₄ Ceramics Fabricated From Carbothermal-reduction-derived Powder

2021 ◽  
Author(s):  
Yuelong Wang ◽  
Xingyu Li ◽  
Haoyang Wu ◽  
Baorui Jia ◽  
Deyin Zhang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Fracture Toughness ◽  
Grain Size ◽  
Flexural Strength ◽  
Grain Boundaries ◽  
Carbothermal Reduction ◽  
Secondary Phase ◽  
Gas Pressure ◽  
Gas Pressure Sintering

Abstract Si3N4-based ceramic (Si3N4-5wt%Y2O3-3wt%MgO) was obtained from carbothermal-reduction-derived powder combined with gas pressure sintering. The phase, microstructure, thermal conductivity and mechanical properties of Si3N4 ceramics were comprehensively analyzed. Dense Si3N4 ceramic with uniform grain size was obtained after sintering at 1900°C for 7 h under a N2 pressure of 1.2 MPa. The secondary phase consisted of Y4Si2O7N2 and Y2Si3O3N4 was found to gather around triangular grain boundaries. The thermal conductivity, flexural strength, hardness and fracture toughness of the Si3N4 ceramics were 95.7 W·m-1·k-1, 715 MPa, 17.2 GPa and 7.2 MPa·m1/2, respectively. The results were compared with product derived from commercial powder, the improvement of thermal conductivity (~8.3%) and fracture toughness (~4.3%) demonstrating the superiority of Si3N4 ceramics prepared from carbothermal-reduction-derived powder.

scholarly journals Influence of Vacuum Heat Treatments on Microstructure and Mechanical Properties of M35 High Speed Steel

Metals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 643
Author(s):  
Chiara Soffritti ◽  
Annalisa Fortini ◽  
Ramona Sola ◽  
Elettra Fabbri ◽  
Mattia Merlin ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Grain Size ◽  
Vickers Hardness ◽  
High Speed ◽  
High Speed Steel ◽  
Plane Strain Fracture Toughness ◽  
Secondary Carbides ◽  
Heat Treated ◽  
Strain Fracture

Towards the end of the last century, vacuum heat treatment of high speed steels was increasingly used in the fabrication of precision cutting tools. This study investigates the influence of vacuum heat treatments at different pressures of quenching gas on the microstructure and mechanical properties of taps made of M35 high speed steel. Taps were characterized by optical microscopy, scanning electron microscopy with energy dispersive spectroscopy, X-ray diffraction, apparent grain size and Vickers hardness measurements, and scratch tests. Failure analysis after tapping tests was also performed to determine the main fracture mechanisms. For all taps, the results showed that microstructures and the values of characteristics of secondary carbides, retained austenite, apparent grain size and Vickers hardness were comparable to previously reported ones for vacuum heat treated high speed steels. For taps vacuum heat treated at six bar, the highest plane strain fracture toughness was due to a higher content of finer small secondary carbides. In contrast, the lowest plane strain fracture toughness of taps vacuum heat treated at eight bar may be due to an excessive amount of finer small secondary carbides, which may provide a preferential path for crack propagation. Finally, the predominant fracture mechanism of taps was quasi-cleavage.

Pressureless Sintering and Properties Investigation of Silicon Nitride

2011 ◽  
Vol 194-196 ◽  
pp. 1464-1469
Author(s):  
Bin Li ◽  
Yi Feng ◽  
Hui Qiang Liu ◽  
Yan Fang Zhu ◽  
Dong Bo Yu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Grain Size ◽  
Bending Strength ◽  
Fracture Morphology ◽  
Pressureless Sintering ◽  
Sintering Aids ◽  
Α Phase ◽  
Different Grain Size ◽  
Si3n4 Ceramics

Different grain size of starting powder was choosed and different sintering additives were used to fabricate Si3N4 ceramics by pressureless sintering. Samples’ relative density and mechanical properties including Vickers hardness, bending strength and fracture toughness were tested. Then XRD, SEM and EDS were carried out to identify phase and observe microstructure and fracture morphology. The result shows that high purity α phase Si3N4 powder of 5 μm is suitable for sintering and combination of 5 wt.% MgO +5 wt.% Y2O3 is most effective within six kinds of sintering aids.

Mechanical Properties of Polycrystalline NiAl from Miniaturized Disk-Bend Tests

1994 ◽  
Vol 364 ◽  
Author(s):  
S. J. Eck ◽  
A. J. Ardell
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Grain Size ◽  
Plastic Zone ◽  
Strain Hardening ◽  
Fracture Stress ◽  
Preliminary Estimate ◽  
Sharp Minimum ◽  
Bend Tests ◽  
True Fracture

AbstractDisk-shaped specimens of polycrystalline NiAl (grain size ∽25 μm), 3 mm in diameter and ranging in thickness from 165 to 370 μm, were indented in their centers to various indentation loads, F, using a Vickers indenter. The yield stress, σy, and apparent fracture stress, σfa, were measured as a function of F, with the indented side in tension, using a miniaturized disk-bend test (MDBT). Fracture does not originate at the indentation for F ≤ 39.2 N. Within this regime of behavior both σy and σfa are slightly larger than in unindented specimens, although σfa passes through a sharp minimum for F < 10 N. For F ≥ 39.2 N fracture originates at the indentations. In this regime σy is essentially constant, but significantly larger than σy at smaller values of F, while σfa decreases steadily with increasing F. We attribute the larger values of σy to strain hardening within the relatively large plastic zone surrounding the indentation. The reduction of σfa with increasing F in this regime occurs because the indentation serves as the point of failure. Fractography reveals NiAl fractures primarily in an intergranular manner. A preliminary estimate of the fracture toughness is 8.54 MPa·a.m1/2, which overestimates the true fracture toughness because σfa exceeds the true fracture stresses.

Sign in / Sign up

Export Citation Format

Share Document