Multifunctional BN/Si3N4 and TiN/Si3N4 Nanocomposites Prepared by In Situ Nitridation Method

2007 ◽  
Vol 336-338 ◽  
pp. 2247-2250
Author(s):  
Lian Gao ◽  
Xi Hai Jin ◽  
Jing Guo Li ◽  
Takafumi Kusunose ◽  
Koichi Niihara
Keyword(s):  
Electrical Resistivity ◽  
Electrical Discharge ◽  
Phase Distribution ◽  
Electrical Discharge Machining ◽  
High Strength ◽  
Second Phase ◽  
Ammonia Gas ◽  
The Matrix

Machinable BN/Si3N4 and electroconductive TiN/Si3N4 nanocomposites were prepared, using powders synthesized through an in-situ nitridation method in flowing ammonia gas. Due to the homogeneous mixing of various components in the powders, nanocomposites with homogeneous second phase distribution in the matrix were obtained. These nanocomposites showed enhanced strengths and distinctive functionalities. BN/Si3N4 nanocomposite with 20-25vol% BN showed a relatively high strength of over 700 MPa and was able to be machined into complicated shapes with diamond bits. Electroconductive TiN/Si3N4 nanocomposite with 25vol% TiN showed a high strength of 1100MPa and low electrical resistivity of 1.1×10-2 ⋅cm, and was promising for electrical discharge machining.

scholarly journals Wire Electrical Discharge Machining, Mechanical and Tribological Performance of TiN Reinforced Multiscale SiAlON Ceramic Composites Fabricated by Spark Plasma Sintering

2021 ◽  
Vol 11 (2) ◽  
pp. 657
Author(s):  
Sergey Grigoriev ◽  
Yuri Pristinskiy ◽  
Marina Volosova ◽  
Sergey Fedorov ◽  
Anna Okunkova ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Spark Plasma Sintering ◽  
Electrical Discharge ◽  
Electrical Discharge Machining ◽  
Ceramic Composites ◽  
Second Phase ◽  
Commercial Sample ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Tin Content

An effective approach for preparing electrically conductive multiscale SiAlON-based nanocomposites with 10 wt.% and 20 wt.% of titanium nitride was developed. Fully dense samples were obtained by spark plasma sintering (SPS) at 1700 °C and 80 MPa for 30 min. The morphology of nanocomposites was observed using scanning electron microscopy and the effects of TiN particles on the mechanical properties and electrical resistivity were studied. It was found that the addition of 20 wt.% TiN increased the hardness and fracture toughness compared to the commercial ceramic analogue TC3030. Meanwhile, the presence of TiN particles reduced the flexural strength of the nanocomposites due to the shrinkage difference between TiN particles and ceramic matrix during cooling, which led to tensile residual stresses and, consequently, to changes in strength values. In addition, the electrical resistivity of nanocomposites decreased with the increase of TiN content and reached 1.6 × 10−4 Ω∙m for 20 wt.% amount of second phase, which consequently made them suitable for electrical discharge machining. In addition to enhanced mechanical and electrical properties, under identical conditions, SPS-sintered multiscale nanocomposites exhibited a higher wear resistance (more than about 1.5-times) compared to the commercial sample due to their higher toughness and hardness.

scholarly journals Multi-Objective Optimization of Wire Electrical Discharge Machining of AL 2124/SIC Composite

2019 ◽  
Vol 9 (1) ◽  
pp. 2155-2163
Keyword(s):  
Electrical Discharge ◽  
Electrical Discharge Machining ◽  
Removal Rate ◽  
High Strength ◽  
Wire Electrical Discharge Machining ◽  
Multi Objective Optimization ◽  
Multi Objective ◽  
Predicted Values ◽  
Pulse On Time ◽  
Pulse Off Time

The growing demand for the use of high strength to weight alloys in industries for manufacturing complex structures challenges the machinability of such advanced materials. In the present investigation, the machinability of SiC particle reinforced Al 2124 composite was studied on Wire electrical discharge machining (WEDM). The process parameters namely pulse on-time (Ton), pulse off time (Toff), peak current (IP), and servo voltage (SV) were optimized by utilizing the central composite design layout. The output responses such as kerf and material removal rate (MRR) were studied in detail. The single and multi-objective optimization was studied for a combination effect using Derringer’s desirability approach and Genetic Algorithm (GA). The experimental and predicted values for each response were validated at the optimized condition. The experimental results were found in line with the predicted values. Multi objective optimization of kerf and MRR by GA showing better result compared to RSM.

Fracture Mechanisms in Laminates in the Alumina - Titania System

2005 ◽  
Vol 290 ◽  
pp. 208-213 ◽  
Author(s):  
S. Bueno ◽  
Carmen Baudín
Keyword(s):  
High Strength ◽  
Fracture Mechanisms ◽  
Second Phase ◽  
Alumina Layer ◽  
Laminated Structure ◽  
Stable Crack Propagation ◽  
Aluminium Titanate ◽  
Intermediate Layers ◽  
Composite Layers

Alumina (Al2O3)-aluminium titanate (Al2TiO5) composites present higher toughness than alumina materials but rather low strength due to microcracking. Laminates in which a flaw tolerant material is located between high strength layers is one way to overcome this problem. In this work, the fracture behaviour of a laminated structure constituted by five layers, where low residual stresses are expected, is studied. In this system, external and central layers of monophase alumina with high strength were combined with intermediate layers of alumina with 10vol.% of aluminium titanate. In the monophase alumina layers, an additional "in situ" formed layer of about 200 µm, constituted by large (@10µm) grains was found, close to the composite layers. The laminated structure presented semistable behaviour during SENVB tests for conditions in which stable crack propagation is not predicted for small grain sized alumina materials. Toughening mechanisms related to thermal expansion mismatch between matrix and second phase in the composite layers and crack bridging in the large grain sized alumina layer were identified.

Preparation of Nano Ti3SiC2/MoSi2 Composite by SPS Process

2011 ◽  
Vol 284-286 ◽  
pp. 2414-2419 ◽  
Author(s):  
Jun Cai Zhang ◽  
Cheng Chang Jia
Keyword(s):  
Mechanical Activation ◽  
Particle Diameter ◽  
Second Phase ◽  
Strong Restriction ◽  
Matrix Surface ◽  
Second Phase Particles ◽  
The Matrix ◽  
Strong Repulsion

In this paper, nano-Ti3SiC2/MoSi2 composite, whose second phase was 20-150nm, was in situ prepared by mechanical activation (MA) and SPS process with the quaternary powers of Mo, Si, Ti, and C. The results showed that: (1) matrix MoSi2 has strong repulsion to other elements, which leads to more second-phase particles inside the matrix rather than on the matrix surface; (2) matrix MoSi2 has strong restriction on the growing of the second phase, which makes the particle diameter of the second phase inside the matrix only in 200 nm around, while that over the surface reaches to 800 nm around.

Continuous and Discontinuous Recrystallization of 6013 Aluminum Alloy

2013 ◽  
Vol 753 ◽  
pp. 221-224 ◽  
Author(s):  
Krzysztof Sztwiertnia ◽  
Magdalena Bieda ◽  
Anna Korneva
Keyword(s):  
Aluminum Alloy ◽  
Grain Boundaries ◽  
Second Phase ◽  
Sheet Plane ◽  
Temperature Range ◽  
Orientation Mapping ◽  
Second Phase Particles ◽  
The Matrix ◽  
Continuous Recrystallization

In situ orientation mapping using TEM and calorimetric measurements were carried out to investigate the annealing behavior of cold-rolled 6013 aluminum alloy. The recrystallization of the material can be considered to be a number of processes that correspond to two separate stored energy release peaks. In the temperature range of the peak 1, the deformation zones around the large second-phase particles acted as sites for particle-stimulated nucleation. In the matrix, at the same time, some elongation of grains occurred. The elongated matrix grains appeared because of the reduction of the dislocation density and the annihilation of some low-angle grain boundaries between chains of subgrains lying in layers parallel to the sheet plane. The matrix processes in this temperatures range can be considered forms of continuous recrystallization. The matrix high-angle grain boundaries started to migrate at the temperature range of the peak 2. They moved mostly in the direction normal to the sheet plane. Heating of the sample for an appropriate time at those temperatures resulted in the complete discontinuous recrystallization of the material. The recrystallized microstructure was dominated now by elongated grains, which were a few times thicker than those obtained by annealing at the temperatures of the peak 1.

Microstructure and Mechanical Properties of X70 Pipeline Steel with High H2S Resistance

2015 ◽  
Vol 816 ◽  
pp. 755-760 ◽  
Author(s):  
Jing Li ◽  
Xiu Hua Gao ◽  
Yong Lu ◽  
Lin Xiu Du
Keyword(s):  
Mechanical Properties ◽  
Pipeline Steel ◽  
High Strength ◽  
Granular Bainite ◽  
Second Phase ◽  
Precipitation Behavior ◽  
Experimental Steel ◽  
X70 Pipeline Steel ◽  
The Matrix ◽  
Sour Service

Anti-H2S X70 pipeline steel was developed. The microstructure of X70 pipeline steel was studied by the analysis of OM, SEM and TEM. The precipitation behavior was discussed. The comprehensive mechanical properties, HIC and SCC performance were systematically studied. The results indicated that the microstructure of the experimental steel was mainly acicular ferrite and granular bainite. The second phase precipitates dispersedly distributed in the matrix. The experimental steel possessed excellent strength, plasticity, low temperature toughness and low yield ratio. And therefore, the X70 pipeline steel in the study is suitable for sour service with the high strength, excellent toughness and low HIC&SSC susceptibility.

scholarly journals Quantitative analysis of microstructure and mechanical properties of Nb–V microalloyed high-strength seismic reinforcement with different Nb additions

2021 ◽  
Vol 40 (1) ◽  
pp. 300-309
Author(s):  
Sheng Huang ◽  
Changrong Li ◽  
Zhiying Li ◽  
Zeyun Zeng ◽  
Yongqiang Zhai ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Dislocation Line ◽  
High Strength ◽  
Second Phase ◽  
Seismic Zone ◽  
Niobium Content ◽  
Precipitated Phase ◽  
Microstructure And Mechanical Properties ◽  
The Matrix

Abstract HRB500E seismic steel bars are mainly used in high-rise buildings near the seismic zone. The influence of different niobium contents (0–0.023%) on the microstructure and mechanical properties of HRB500E seismic reinforcement was studied. Results showed that the grain size of ferrite was between 3.6 and 8.3 μm when only V was added. Meanwhile, as the niobium content increases, the ferrite particles are further refined. After adding niobium, the grain contribution increased by 9%. The addition of niobium significantly refined the grain size of HRB500E seismic reinforcement. The second-phase nano-elliptic precipitate is NbC. The precipitated phase is dispersed on the grain boundary and the matrix, and the dislocation density on the matrix promotes the precipitation of NbC particles along the dislocation line. The second-phase precipitation of niobium can form an effective pinning effect and then refine the pearlite spacing. The microhardness and the tensile strength also significantly improved. The yield strength increased from 509 to 570 MPa.

scholarly journals Interpretation of Specific Strength-Over-Resistivity Ratio in Cu Alloys

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7150
Author(s):  
Hongming Li ◽  
Shuang Zhang ◽  
Yajun Zhao ◽  
Xiaona Li ◽  
Fushi Jiang ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Lower Limit ◽  
High Strength ◽  
Alloy System ◽  
Resistivity Ratio ◽  
Specific Strength ◽  
Cu Alloys ◽  
The Matrix ◽  
In Series ◽  
Pure Cu

Reaching simultaneously high mechanical strength and low electrical resistivity is difficult as both properties are based on similar microstructural mechanisms. In our previous work, a new parameter, the tensile strength-over-electrical resistivity ratio, is proposed to evaluate the matching of the two properties in Cu alloys. A specific ratio of 310 × 108 MPa·Ω−1·m−1, independent of the alloy system and thermal history, is obtained from Cu-Ni-Mo alloys, which actually points to the lower limit of prevailing Cu alloys possessing high strength and low resistivity. The present paper explores the origin of this specific ratio by introducing the dual-phase mechanical model of composite materials, assuming that the precipitate particles are mechanically mixed in the Cu solid solution matrix. The strength and resistivity of an alloy are respectively in series and parallel connections to those of the matrix and the precipitate. After ideally matching the contributions from the matrix and the precipitate, the alloy should at least reach half of the resistivity of pure Cu, i.e., 50%IACS, which is the lower limit for industrially accepted highly conductive Cu alloys. Under this condition, the specific 310 ratio is related to the precipitate-over-matrix ratios for strength and resistivity, which are both two times those of pure Cu.

Mismatch and misorientation at the precipitate/matrix interface in an Al-Zralloy

1983 ◽  
Vol 41 ◽  
pp. 242-243
Author(s):  
Angus Porter ◽  
Louise Makin ◽  
Brian Ralph
Keyword(s):  
High Strength ◽  
Second Phase ◽  
Exact Nature ◽  
Matrix Interface ◽  
Single Image ◽  
Second Phase Particles ◽  
The Matrix ◽  
Lattice Planes ◽  
Zr Alloy ◽  
Zr Alloys

Much of the hardening of high strength aluminium alloys containing zirconium results from the precipitation of the metastable γ' (Al3Zr) phase (Ll2 structure, cube/cube related to the matrix). There exists some controversy in the literature as to the magnitude of the matrix (γ)-γ' misfit in Al-Zr alloys; the values reported range from 1% down to rather less than half this figure. In the present paper, the use of moire fringe imaging to study mismatch and misorientation between the γ and γ' lattice in a binary Al-Zr alloy will be considered. The advantages of this technique for the study of small second-phase particles are three-fold. The information obtained is specific to a single particle; the exact nature of the particle/matrix interface is unimportant, as long as the two lattices exhibit nearly coincident diffraction maxima; and mismatch and misorientation of particular sets of lattice planes can be determined from a single image.

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