scholarly journals Mechanical Properties, Thermal Stability and Microstructures of W-Re-ZrC Alloys Fabricated by Spark Plasma Sintering

Metals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 277 ◽  
Author(s):  
Shu Miao ◽  
Zhuoming Xie ◽  
Yan Lin ◽  
Qianfeng Fang ◽  
Jinhong Tan ◽  
...  

Tungsten materials, used as friction stir welding tools, undergo severe plastic deformation and even collapse at high operating temperatures. In order to improve the low-temperature toughness and high-temperature strength, W-10wt.%Re-0.5wt.%ZrC alloys were processed by high-energy ball milling and subsequent spark plasma sintering. Single solid-solution W-Re powders with typical body-centered cubic structures were achieved when the milling time increases to 50 h. The microhardness, tensile properties, thermal stability and microstructures of this sintered W-10wt.%Re-0.5wt.%ZrC alloys were investigated. Synergetic effects of the solute Re and nanosized dispersion particles induce improvements in low-temperature toughness and high-temperature strength. The alloy suffers ductile fracture at 300 °C, which is about 400 °C and 300 °C lower than that of the spark plasma sintered pure W and W-0.5wt.%ZrC, respectively. Besides, this W-10wt.%Re-0.5wt.%ZrC has a high ultimate tensile strength of 818 MPa and uniform elongation of ~ 8.1% at 300 °C. Moreover, the microstructures and hardness remain stable even after 1500 °C anneal. Based on a detailed microstructure analysis, the mechanisms for the enhanced strength, low-temperature ductility and high thermal stability are proposed and discussed. Grain boundary mobility is impeded by the kinetics constraint through dispersed particles pinning and solute Re atoms dragging, which leads to improved thermal stability. The formation of Zr-C-O particles is most probably attributed to ZrC particles capturing and interacting with impurity oxygen during sintering.

2014 ◽  
Vol 783-786 ◽  
pp. 1099-1104 ◽  
Author(s):  
Somayeh Pasebani ◽  
Aniket K. Dutt ◽  
Indrajit Charit ◽  
Rajiv S. Mishra

There is a need to enhance or develop high temperature capabilities of structural materials for advanced coal‐fired power plants. These materials require a combination of high temperature strength, creep resistance and corrosion resistance in the oxygen‐rich and hydrogen‐rich high pressure environments. In this study, atomized Ni‐20Cr (wt.%) powder was mechanically milled with Y2O3 nanopowder (30‐40 nm powder size) to produce an alloy with a chemical composition of Ni‐20Cr‐1.2Y2O3 (wt.%) alloy using high energy ball milling. To minimize agglomeration during milling, 1 wt.% stearic acid was added to the powder mixture prior to milling. Microstructural characteristics of the powder were primarily characterized by the X‐ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The crystallite size and lattice strain were measured by XRD whereas powder morphology (powder size, shape) was studied by SEM. A milling time of 2 h was found to be optimal for the purpose that yttria particles are not dissolved yet uniformly distributed. Subsequently, the milled powder was consolidated into bulk specimens (12.5 mm in diameter) via spark plasma sintering (SPS) at 1100 °C for 30 minutes. Following SPS, the density and hardness of the specimens were measured. Microstructural characterization of the SPSed specimens was performed using SEM and TEM. The microstructural characteristics were correlated with the measured mechanical properties.


2006 ◽  
Vol 21 (6) ◽  
pp. 1460-1466 ◽  
Author(s):  
Diletta Sciti ◽  
Laura Silvestroni ◽  
Alida Bellosi

HfB2–15 vol% MoSi2 composites were produced from powder mixtures and densified through different techniques, namely hot pressing and spark plasma sintering. Dense materials were obtained at 1900 °C by hot pressing and at 1750 °C by spark plasma sintering. Microstructure and mechanical properties were compared. The most relevant result was for high-temperature strength: independent of the processing technique, the flexural strength in air at 1500 °C was higher than 500 MPa.


2016 ◽  
Vol 99 (8) ◽  
pp. 2769-2777 ◽  
Author(s):  
Dmytro Demirskyi ◽  
Ievgen Solodkyi ◽  
Yoshio Sakka ◽  
Oleg Vasylkiv

2005 ◽  
Vol 287 ◽  
pp. 166-170 ◽  
Author(s):  
Xin Xu ◽  
Toshiyuki Nishimura ◽  
Naoto Hirosaki ◽  
Rong Jun Xie ◽  
Yoshinobu Yamamoto

The fabrication of dense Si3N4 nano-ceramics via a high-energy mechanical milling process and subsequent spark plasma sintering (SPS) was reported in this paper. A thermodynamically stable β-Si3N4 powder mixed with 5-mol% Y2O3 and 2-mol% Al2O3 was used as starting powders for high-energy mechanical milling. Milling resulted in the significant decrease of crystalline size and the amorphization of the starting powders. Based on XRD measurements, the amount of the amorphous phase and the grain sizes of the remaining crystalline silicon nitride depended on the charge ratio. Milled powders could be SPSed at relatively low temperature. A homogenous dense silicon nitride ceramics with grain diameter of about 70 nm could be fabricated through SPS at a low temperature of 1600oC for 5 min. The significant decrease of grain size greatly increased the hardness of obtained ceramics.


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