Large strain hardening of magnesium containing in situ nanoparticles

Abstract In this work, in situ magnesium-based composite composed of nanoscale magnesium oxide (MgO), prepared by spark plasma sintering, shows significant plasticity and high strain hardening. During the strain-hardening stage, the incremental work-hardening exponent shows drastic fluctuations due to the pile-up and release of dislocations. The dislocation pile-up at the interface makes it possible to form dislocation cells. Mixed dislocations can be generated within the cells surrounding the MgO particles, which can interact with the stress field and effectively hinder the movement of dislocations, leading to an increase in dislocation density. What is more, grain boundaries have higher elastic modulus and hardness, which may lead to the appearance of microcracks and eventually intergranular fractures. Our results may shed some light on understanding the role of MgO particles in influencing the mechanical properties of Mg alloys and Mg-based composites, especially in work hardening.

Download Full-text

Role of Ti3AlC2 MAX phase on characteristics of in-situ synthesized TiAl intermetallics. Part I: sintering and densification

Synthesis and Sintering ◽

10.53063/synsint.2021.1347 ◽

2021 ◽

Vol 1 (3) ◽

pp. 169-175

Author(s):

Maryam Akhlaghi ◽

Esmaeil Salahi ◽

Seyed Ali Tayebifard ◽

Gert Schmidt

Keyword(s):

Max Phase ◽

Displacement Rate ◽

Heating Process ◽

Aluminum Powders ◽

Plasma Sintering ◽

Rate Versus ◽

Spark Plasma ◽

Composite Samples

Five TiAl–Ti3AlC2 composite samples containing (10, 15, 20, 25 and 30 wt% Ti3AlC2 MAX phase) were prepared by spark plasma sintering technique at 900 °C for 7 min under 40 MPa. For this purpose, metallic titanium and aluminum powders (aiming at the in-situ formation of the TiAl matrix phase) were ball-milled with predetermined contents of Ti3AlC2 MAX phase, which already was synthesized using the same metallic powders as well as graphite flakes. Displacement-time-temperature variations during the heating and sintering steps, displacement rate versus temperature, displacement rate versus time, and densification behavior were studied. Two sharp changes were detected in the diagrams: the first one, ~16 min after the start of the heating process due to the melting of Al, and the second one, after ~35 min because of the sintering progression and the applied final pressure. The highest relative densities were measured for the samples doped with 20 and 25 wt% Ti3AlC2 additives. More Ti3AlC2 addition resulted in decreased relative density because of the agglomeration of MAX phase particles.

Download Full-text

Electric Current-Assisted Joining of Copper Plates Using Silver Formed by In-Situ Decomposition of Ag2C2O4

Metals ◽

10.3390/met8070538 ◽

2018 ◽

Vol 8 (7) ◽

pp. 538 ◽

Cited By ~ 1

Author(s):

Dina Dudina ◽

Alexander Matvienko ◽

Anatoly Sidelnikov ◽

Mikhail Legan ◽

Vyacheslav Mali ◽

...

Keyword(s):

Shear Strength ◽

Electric Current ◽

Reference Sample ◽

Silver Layer ◽

Metallic Silver ◽

Plasma Sintering ◽

Spark Plasma ◽

In Situ Decomposition

Pulsed electric current can be used for the fast sintering of powders as well as joining of macroobjects. In this work, we brazed copper plates using a silver layer that was formed in situ by the decomposition of a silver oxalate Ag2C2O4 powder placed between the plates. Joining was conducted in the chamber of a Spark Plasma Sintering (SPS) facility with and without a graphite die. In the die-assisted tooling configuration, indirect heating of the assembly from the graphite die carrying electric current occurred until the brazing layer transformed into metallic silver. The passage of electric current through a Cu/Ag2C2O4/Cu stack placed between the electrodes without a die was possible because of the formation of Cu/Cu contacts in the areas free from the Ag2C2O4 particles. Joints that were formed in the die-assisted experiments showed a slightly higher shear strength (45 MPa) in comparison with joints formed without a die (41 MPa). The shear strength of the reference sample (obtained without a die), a stack of copper plates joined without any brazing layer, was only 31 MPa, which indicates a key role of the silver in producing strong bonding between the plates. This study shows that both die-assisted tooling configurations and those without a die can be used for the SPS brazing of materials by the oxalate-derived silver interlayer.

Download Full-text

Study on mechanical properties and wear behavior of in-situ synthesized CNTs/ CuCrZrY composites prepared by spark plasma sintering

Vacuum ◽

10.1016/j.vacuum.2021.110180 ◽

2021 ◽

pp. 110180

Author(s):

Honglei Zhou ◽

Xiaohong Chen ◽

Ping Liu ◽

Weidong Wang ◽

Wen Liu

Keyword(s):

Mechanical Properties ◽

Spark Plasma Sintering ◽

Wear Behavior ◽

Plasma Sintering ◽

Spark Plasma

Download Full-text

Microstructure and properties of nano-laminated Y3Si2C2 ceramics fabricated via in situ reaction by spark plasma sintering

Journal of Advanced Ceramics ◽

10.1007/s40145-021-0459-0 ◽

2021 ◽

Vol 10 (3) ◽

pp. 578-586

Author(s):

Lin-Kun Shi ◽

Xiaobing Zhou ◽

Jian-Qing Dai ◽

Ke Chen ◽

Zhengren Huang ◽

...

Keyword(s):

Spark Plasma Sintering ◽

Atomic Scale ◽

Max Phase ◽

X Ray Diffraction ◽

Selected Area Electron Diffraction ◽

Plasma Sintering ◽

Transmission Electron ◽

Spark Plasma ◽

Diffraction Patterns

AbstractA nano-laminated Y3Si2C2 ceramic material was successfully synthesized via an in situ reaction between YH2 and SiC using spark plasma sintering technology. A MAX phase-like ternary layered structure of Y3Si2C2 was observed at the atomic-scale by high resolution transmission electron microscopy. The lattice parameters calculated from both X-ray diffraction and selected area electron diffraction patterns are in good agreement with the reported theoretical results. The nano-laminated fracture of kink boundaries, delamination, and slipping were observed at the tip of the Vickers indents. The elastic modulus and Vickers hardness of Y3Si2C2 ceramics (with 5.5 wt% Y2O3) sintered at 1500 °C were 156 and 6.4 GPa, respectively. The corresponding values of thermal and electrical conductivity were 13.7 W·m-1·K-1 and 6.3×105 S·m-1, respectively.

Download Full-text