scholarly journals Analysis of the In Situ Crack Evolution Behavior in a Solid Solution Mg-13Gd-5Y-3Zn-0.3Zr Alloy

Materials ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 36
Author(s):  
Yaqin Yang ◽  
Chongli Mu ◽  
Zhongjian Han ◽  
Jian Xu ◽  
Baocheng Li
Keyword(s):  
Solid Solution ◽  
Stress Concentration ◽  
High Performance ◽  
Solution Treatment ◽  
High Strength ◽  
Lpso Phase ◽  
Stacking Order ◽  
Micro Cracks ◽  
Evolution Behavior

The low plasticity of high strength Mg-Gd-Y alloy has become the main obstacle to its application in engineering. In this paper, the origin, propagation and fracture processes of cracks of a solution of treated Mg-13Gd-5Y-3Zn-0.3Zr alloy were observed and studied with scanning electron microscopy (SEM) in an in situ tensile test to provide theoretical references for the development of a new high-performance Mg-Gd-Y alloy. The results showed that there was still some bulk long period stacking order (LPSO) phase remaining in solid solution Mg-13Gd-5Y-3Zn-0.3Zr alloy. Most importantly, it was found that the locations of micro-cracks vary with the different solution treatment processes, mainly including the following three types. (1) At 480 × 10 h and 510 °C × 10 h, much bulk LPSO phase with higher elastic modulus remains in the alloy, which can lead to micro-cracks in the LPSO phase due to stress concentration. (2) At 510 °C × 13 h and 510 °C × 16 h, the phase structure of bulk LPSO changes, and the stress concentration easily appears at the LPSO/α-Mg interface, which leads to micro-cracks at the interface. (3) At 510 °C × 19 h and 510 °C × 22 h, the grain size increases, and the stress concentration is obvious at the grain boundary of coarse grains, which leads to the formation of micro-cracks.

scholarly journals Microstructural evolution and mechanical properties of nano-ATZ ceramics by solid solution precipitation

2021 ◽  
Author(s):  
Yongdong Yu ◽  
Xudong Liu ◽  
Yuchen Yuan ◽  
Wanjun Yu ◽  
Hang Yin ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Solid Solution ◽  
High Performance ◽  
High Hardness ◽  
High Strength ◽  
Low Density ◽  
Single Edge ◽  
High Toughness ◽  
Beam Method

Abstract Alumina toughened zirconia (ATZ) nanoceramics with high-strength, high-toughness and high-hardness were prepared by in-situ nanoprecipitation from solid solution micro-powders. The submicron Al2O3 (~ 450 nm) and ZrO2 (~ 350 nm) grains contained low-density precipitated nano-ZrO2 (~ 40 nm) and nano-Y4Al2O9 (YAM, ~ 90 nm) particles, respectively, making high-performance nano-ATZ ceramics with ultrafine intracrystalline nanostructure yet achieved. There was a parallel or eutectic lattice orientation relationship between the submicrocrystals and its internal nanoparticles of their crystal planes, which is very conducive to the improvement of the mechanical properties of nano-ATZ ceramics. The fracture toughness and hardness of 30wt%Al2O3/70wt%ZrO2(3mol%Y2O3) can be as high as 5.68 ± 0.17 MPa·m1/2 (single-edge V-notched beam method, SEVNB) and 16.32 ± 0.45 GPa, respectively, which are improved by ~ 25 % and ~ 20 % compared with those of 3Y-TZP ceramics. Therefore, this method can be used to prepare nano-ATZ ceramics contained ultrafine nanoparticles and uniform distribution of Al2O3 phases.

Reaction Synthesized Boron Nitride-Containing Composites (BNCC)

2007 ◽  
Vol 280-283 ◽  
pp. 1385-1390
Author(s):  
Guo Jun Zhang ◽  
Tatsuki Ohji ◽  
Shuzo Kanzaki
Keyword(s):  
Boron Nitride ◽  
Hot Pressing ◽  
High Performance ◽  
Hexagonal Boron Nitride ◽  
High Strength ◽  
Reactive Sintering ◽  
Boron Source ◽  
Inorganic Reactions ◽  
Reactive Hot Pressing

Based on the proposed inorganic reactions a series of high performance hexagonal boron nitride-containing composites (BNCC), include SiC-BN, Si3N4-SiC-BN, SiAlON-BN, AlN-BN, Al2O3-BN, AlON-BN and mullite-BN, have been prepared via reactive hot pressing or pressureless reactive sintering. Various boron-bearing components such as B, B4C, AlB2, SiB4, SiB6, B2O3 or H3BO3, 9Al2O3×2B2O3 (9A2B) and 2Al2O3×B2O3 (2AB) are used as the boron source. On the other hand, nitrogen gas or solid state nitirgen-bearing metal nitrides such as Si3N4 and AlN can be used as the nitrogen source. The in situ synthesized composites demonstrated homogeneous and isotropical microstructures with very fine (nano-sized) BN platelets or their agglomerates distributed in the matrixes. These composites showed high strength, low elasticity and improved strain tolerance. In this article the reaction design, thermodynamics, reaction mechanisms, reactive hot pressing or pressureless reactive sintering, microstructures and mechanical properties will be discussed.

Thermal Stability and Mechanical Properties of Extruded Mg-Zn-Y Alloys with Long-Period Stacking Order Phase

2010 ◽  
Vol 654-656 ◽  
pp. 611-614 ◽  
Author(s):  
Masafumi Noda ◽  
Yoshihito Kawamura
Keyword(s):  
Mechanical Properties ◽  
Thermal Stability ◽  
High Strength ◽  
Grain Boundary Sliding ◽  
Temperature Deformation ◽  
Kink Bands ◽  
Lpso Phase ◽  
Fine Grained ◽  
Stacking Order ◽  
Boundary Sliding

Magnesium alloys are very attractive in such applications as automotive and aerospace. However, the mechanical properties of Mg alloys are inferior to those of Al alloys, and this limits their range of applications. In the present study, effects of annealing on the mechanical properties and the thermal stability of the microstructure in LPSO Mg-Zn-Y extruded alloys were investigated. Even when elongation showed 10% with having maintained high strength to annealing temperature at 573 K for 3.6 ks, and this alloy extended annealing time for 1.0 kh, LPSO phase did bent and was able to confirm kink bands. On the other hand, α-Mg phase was fine structure without pronounced grain growth. In elevated temperature deformation of as extruded and annealed materials, LPSO phase did finely dispersed to α-Mg phase by grain boundary sliding of α-Mg phase, but fracture did not occurred in the interface between LPSO and α-Mg phases. Kink bands introduced in LPSO phase during plastic deformation and fine-grained α-Mg phase were important to obtained of high strength and ductility.

Accelerated degradation rate of high-strength Mg-4Y-1Zn alloy by Cu addition for degradable bridge-plug applications

2020 ◽  
Vol 111 (10) ◽  
pp. 872-875
Author(s):  
Baosheng Liu ◽  
Gehang Dong ◽  
Xiaoxia Ren ◽  
Yuezhong Zhang ◽  
Yinghui Wei
Keyword(s):  
Degradation Rate ◽  
Corrosion Potential ◽  
High Strength ◽  
Compressive Properties ◽  
Rapid Degradation ◽  
Lpso Phase ◽  
Accelerated Degradation ◽  
Long Period ◽  
Stacking Order ◽  
High Fraction

Abstract To find good candidate materials for degradable bridgeplugs used in shale oil or gas exploitation, a novel hot extruded Mg-4Y-1Zn-1Cu alloy with long period stacking order (LPSO) phase and excellent mechanical properties and rapid degradation rate was fabricated. Compared with the Mg-4Y-1Zn alloy, the compressive properties of Mg-4Y- 1Zn-1Cu alloy are dramatically enhanced by adding Cu, with a compressive strength of 480 MPa, which can be attributed to the formation of fine-grains and the strengthening LPSO phase distributed within the substrate. Furthermore, Mg-4Y-1Zn-1Cu alloy shows a rapid degradation rate as demonstrated by immersion tests and polarization curves, with about 30 times higher corrosion rate than Mg- 4Y-1Zn alloy, which can be attributed to the 14H-type LPSO phase containing Cu with high corrosion potential and high fraction grain boundaries.

Rehydration of Ultra High Performance Concrete

2014 ◽  
Vol 897 ◽  
pp. 275-279 ◽  
Author(s):  
Ulrich Diederichs ◽  
Iris Marquardt ◽  
Vít Petranek
Keyword(s):  
Water Vapor ◽  
Water Uptake ◽  
High Performance ◽  
High Performance Concrete ◽  
High Strength ◽  
Porous System ◽  
Ultra High Performance Concrete ◽  
Micro Cracks ◽  
Maximum Temperatures ◽  
Subsequent Storage

Ultra High Performance Concrete (UHPC) and High Strength Concrete (USC) are because of the high density of their matrices very susceptible to spalling during fire exposure. By aid of a heat treatment with maximum temperatures of about 450°C a network of capillaries and micro cracks could be formed, which leads like a porous medium to a relief of water vapor already at harmless low pressures and could prevent the materials from spalling. In the framework of the presented study on UHPC some orientating tests have been performed to obtain knowledge concerning alterations of the microstructure during thermal treatment at 150°C, 250°C, 350°C and 450°C and the subsequent storage in air with 100% relative humidity at 20°C as to allow water uptake and rehydration. The tests have shown that by aid of the said treatment generation of a respective porous system was achieved, which remained open for the transport of water vapor at high temperatures, also after water uptake and rehydration of the dehydrated cementitious matrix. However further studies are needed to get information about effects of the treatments on the mechanical properties and the durability of members.

Role of Reinforcement Particle Size and Its Dispersion on Room Temperature Dry Sliding Wear of AA7075/TiB2 Composites

2022 ◽  
Vol 10 (1) ◽  
pp. 1-13
Author(s):  
Vinod Kumar V. Meti ◽  
G. U. Raju ◽  
I. G. Siddhalingeshwar ◽  
Vinayak Neelakanth Gaitonde
Keyword(s):  
Particle Size ◽  
Wear Resistance ◽  
High Performance ◽  
Base Alloy ◽  
High Strength ◽  
Reinforcement Particle ◽  
Dry Sliding Wear ◽  
Pin On Disc ◽  
Tib2 Particles

Aluminum alloy based metal matrix composites (AMCs) are widely accepted material in the aerospace, automotive, military, and defence applications due to lightweight and high strength. For tribological applications, high-performance wear-resistant materials like AMCs are the candidate materials. In this investigation, AA7075 based composites with different size TiB2 particles were fabricated using in-situ and ultrasound casting techniques (UST). The AMCs were tested using pin-on-disc tribo tester and the effects of different sized TiB2 particles on wear resistance of AA7075/TiB2 composites have been investigated. The wear resistance of AA7075/TiB2 composite fabricated using UST is found to significantly improve when compared to base alloy and also in-situ composite due to refinement in the particle size, reduced the agglomeration, and improved the distribution of TiB2 particles. The test results also revealed the existence of a mixture of mechanically mixed Al–Zn–Fe intermetallic alloy and oxides of these elements.

Creep Studies of Monolithic Phases in Nb-Silicide Based In-Situ Composites

2000 ◽  
Vol 646 ◽  
Author(s):  
B.P. Bewlay ◽  
C.L. Briant ◽  
E.T. Sylven ◽  
M.R. Jackson ◽  
G. Xiao
Keyword(s):  
Solid Solution ◽  
Creep Rate ◽  
Creep Resistance ◽  
High Strength ◽  
Aircraft Engine ◽  
Great Promise ◽  
In Situ Composites ◽  
Monolithic Phases ◽  
The Individual

ABSTRACTNb-silicide composites combine a ductile Nb-based solid solution with high-strength silicides, and they show great promise for aircraft engine applications. Previous work has shown that the silicide composition has an important effect on the creep rate. If the Nb:(Hf+Ti) ratio is reduced below ∼1.5, the creep rate increases significantly. This observation could be related to the type of silicide present in the material. To understand the effect of each phase on the composite creep resistance, the creep rates of selected monolithic phases were determined. To pursue this goal, monolithic alloys with compositions similar to the Nb-based solid solution and to the silicide phases, Laves, and T2 phases, were prepared. The creep rates were measured under compression at 1100 and 1200°C. The stress sensitivities of the creep rates of the monolithic phases were also determined. These results allow quantification of the load bearing capability of the individual phases in the Nb-silicide based in-situ composites.

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