solid solution strengthening
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2022 ◽  
Vol 210 ◽  
pp. 114470
Author(s):  
Pramote Thirathipviwat ◽  
Shigeo Sato ◽  
Gian Song ◽  
Jozef Bednarcik ◽  
Kornelius Nielsch ◽  
...  

2022 ◽  
Vol 60 (1) ◽  
pp. 14-25
Author(s):  
Hanjung Kwon

The metallic binder in WC-Co hard metals was effectively strengthened using the solid solution phases of Co and W. These metallic phases of Co and W (Co1-xWx, x<1), which consist of two kinds of structures (FCC and HCP), were successfully formed by hydrogen reduction of milled oxides mixtures (Co3O4 and WO3) at over 1000 oC. When hard metals are fabricated by pressureless sintering of mixed WC and Co1-xWx, the hard metals containing the WC2 and M6C phases (Co2W4C and Co4W2C) have brittleness, which degrades their mechanical properties, like hard metals fabricated from mixtures of WC, Co, and W. By rapidly sintering the WC-Co1-xWx hard metals for 5 min the WC2 and M6C phases were eliminated, and a two-phase (WC and the metallic phase of Co and W) region was successfully obtained. The mechanical properties of the WC-Co1-xWx hard metals showed higher values for both hardness (max. 18.8 GPa) and fracture toughness (8.5 MPa·m1/2) than conventional WC-Co hard metal (HV: 15.9 GPa, KIC: 6.9 MPa·m1/2). The enhancement in toughness was attributed to the solid solution strengthening of the metallic binder and the elimination of the WC2 and M6C phases. The suppression of grain growth due to the short duration of sintering also played a positive role in improving the hardness of the WC-Co1-xWx hard metals. The phase-controlled solid solution metallic binder could be the key material to enhance the hardness and toughness of hard metals.


Materials ◽  
2022 ◽  
Vol 15 (1) ◽  
pp. 355
Author(s):  
Ao Fu ◽  
Yuankui Cao ◽  
Yuxi Liu ◽  
Shenghang Xu

A series of novel lightweight TaNbVTi-based refractory high entropy alloys (RHEA) were fabricated through ball-milling and spark plasma sintering (SPS). The reinforced phase of TiO precipitates were in-situ formed due to the introduction of Al2O3 ceramic particles. The RHEA with 15% Al2O3 exhibits a high compressive yield strength (1837 MPa) and a low density (7.75 g/cm3) with an adequate ductility retention. The yield strength and density are 32% higher and 15% lower, respectively, compared to the RHEA without Al2O3 addition. The specific yield strength (237 MPa cm3/g) of the RHEAs is much higher than that of other reported RHEAs, and is mainly ascribed to the introduction of high volume fraction of Al2O3 additives, resulting in solid solution strengthening and precipitation strengthening. Meanwhile, the ductile matrix is responsible for the good compressive plasticity.


2021 ◽  
Author(s):  
Jiquan Huang ◽  
Changliang YANG ◽  
Qiufeng HUANG ◽  
Zhonghua DENG ◽  
Yun WANG ◽  
...  

Abstract Sesquioxides such as Y2O3 and Sc2O3 are important optical materials, but the fabrication of their transparent ceramics remains a challenge due to the ultra-high melting point of over 2400 oC. In this work, a series of (Y1-xScx)2O3 transparent ceramics were successfully fabricated by a simple vacuum sintering process without any sintering additives, and the effect of Scandium (Sc) content on the crystal structure and optical/thermal/mechanical properties were evaluated. Y2O3 and Sc2O3 form a complete solid solution with a cubic bixbyite structure. The formation of (Y1-xScx)2O3 solid solution promotes the densification of ceramics, leading to the realization of high transparency close to the theoretical transmittance over a wide wavelength range of 0.35-8 mm. In particular, the in-line transmittance in the range of 0.6-6 mm remains above 80% for (Y1-xScx)2O3 with x = 0.23-0.31, while the pristine Y2O3 and Sc2O3 are opaque. Moreover, the mechanical properties including Vickers hardness (Hv), fracture toughness (KIC), and biaxial strength (δb) are evidently enhanced due to the solid solution strengthening, while the thermal conductivity is reduced due to the reduction of photon free path. This study demonstrates that forming of solid solution is a facile and universal approach for preparing sesquioxides transparent ceramics with high optical and mechanical quality.


Metals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1909
Author(s):  
Lukas Haußmann ◽  
Hamad ur ur Rehman ◽  
Dorothea Matschkal ◽  
Mathias Göken ◽  
Steffen Neumeier

Solid solution strengthening of the unordered γ matrix phase by alloying elements is of great importance during creep of Ni-based superalloys, particularly at high temperatures above 1000 °C. To study the role of different potent solutes, we have conducted creep experiments on binary Ni-2X alloys (X = Mo, Re, Ta, W) at 1000 °C, 1050 °C, and 1100 °C at a constant stress of 20 MPa. Compared to mechanical tests below 800 °C, where the size of the elements mostly determines the solid solution hardening contribution, the strengthening contribution of the different alloying elements above 1000 °C directly correlates with their diffusivity. Therefore, elements such as Ta that lead to strong solid solution hardening at low temperatures become less effective at higher temperatures and are exceeded by slower diffusing elements, such as Re.


Author(s):  
James M. Borgman ◽  
Jing Wang ◽  
Lorenzo Zani ◽  
Paul P. Conway ◽  
Carmen Torres-Sanchez

AbstractIn this study, Ti-(0-30 wt.%)Nb alloys developed from elemental powders were fabricated by the Selective Laser Melting (SLM) process. Compositional homogeneity, microstructure and mechanical performance were investigated as a function of energy density. The proportion of un-melted Nb particles and isolated pore count reduced with increasing energy density, while Ti allotropic content (i.e. α’, α” and β) varied with energy density due to in-situ alloying. Increasing the Nb content led to the stabilisation of the α” and β phases. The mechanical properties were similar to those compositions manufactured using casting methods, without further post processing. The addition of 20Nb (wt.%) and using an energy density of 230 J/mm3 resulted in a Young’s Modulus of 65.2 ± 1.8 GPa, a yield strength of 769 ± 36 MPa and a microstructure of predominantly α” martensite. This strength to stiffness ratio (33% higher than Ti-10Nb and 22% higher than Ti-30Nb), is attributed to in-situ alloying that promotes solid solution strengthening and homogenisation. These alloys are strong contenders as materials suitable for implantable load-bearing orthopaedic applications.


Author(s):  
Farhan Ashraf ◽  
Gustavo M. Castelluccio

AbstractThe mechanical response of metallic materials is controlled by multiple deformation mechanisms that coexist across scales. Dislocation glide is one such process that occurs after bypassing obstacles. In macroscopic well-annealed single-phase metals, weak obstacles such as point defects, solid solution strengthening atoms, short-range dislocation interactions, and grain boundaries control dislocation glide by pinning the scarce dislocation density. This work investigates the dislocation glide energy barrier in face-centered cubic (FCC) metallic materials by considering a crystal plasticity model that computes the yield strength as a function of temperature. The dislocation glide energy barrier is parameterized by three different formulations that depend on two parameters. A Monte Carlo analysis randomly determines all other coefficients within uncertainty bounds identified from the literature, followed by fitting the two energy barrier parameters to experimental data. We consider ten FCC materials to demonstrate that the methodology characterizes robustly the dislocation glide energy barrier used by crystal plasticity models. Furthermore, we discovered a correlation between the glide barrier and the stacking fault energy that can be used as a basis to infer the glide activation energy. Graphical abstract


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