Superplasticity and high temperature deformation behaviour in nano grain Tungsten compacts

Abstract

Nano grain tungsten is fabricated by Mechanical Milling (MM) process, and its grain growth behavior and high temperature deformability is investigated. As a result, a nano grain structure, whose grain size is approximately 20 nm or less, is obtained after MM for 360ks. Those nano grains demonstrate an irregular grain boundary structure, i.e., "non-equilibrium grain boundary", and they change to a smooth grain boundary structure by annealing at 1023 K for 3.6 ks. Compacts with nano grain structure indicate superior sintering property even at 1273 K (0.35 T m ). Rhenium addition prevents grain growth during sintering and thus the compacts indicate a further improvement in deformability. The compact is composed of equiaxed grain, whose grain size is 420 nm, and has low dislocation density even after the large deformation. The strain rate sensitivity, i.e., m-value, of 0.41 is obtained in the W-Re compact at 1473 K. Those results strongly imply that the nano grain W-Re compacts show superplasticity at less than half of the melting temperature, i.e., 1473 K (0.42 of the solidus temperature).

Effect of Ball Milling Parameters on the Refinement of Tungsten Powder

“…Recent research has shown that the refinement of tungsten grain size can improve its mechanical properties, such as the enhancement of its ductility [9][10][11][12]. Many methods have been proposed to refine the grain size, such as equal channel angular extrusion (ECAE) [13,14], high-pressure torsion (HPT) [15,16], accumulative roll bonding (ARB) [17,18], surface mechanical attrition treatment (SMAT) [19,20], and high-energy ball milling [21][22][23][24][25][26].…”

Management of composition cathodic products in the electrolysis of molybdenum‐, tungsten‐ and carbon‐ bearing halogenide‐oxide and oxide melts

“…Research results of the cathode products composition molten in a systems NaCl-LiF-Na 2 MoO 4 (Na 2 WO 4 )-Na 2 CO 3 and Na 2 WO 4 -Li 2 MoO 4 (Li 2 WO 4 , MoO 3 , WO 3 )-Li 2 CO 3 have shown that for plating coating by the high-temperature electrochemical synthesis method may be offered above mentioned electrolytes. Areas of electrowinning of molybdenum, tungsten, their bronzes and carbides, carbon are identified.…”

“…Increased interest in the development of new and effective methods for obtaining refractory compounds – carbides, borides, silicides, alloys and intermetallic compounds of metals of IV–VI B groups is dictated by their use for the needs of modern technology . Comparative analysis of existing methods for the synthesis of metal‐like refractory compounds showed that one of the most promising, but so far little studied is the method of high‐temperature electrochemical synthesis .…”

Acidic‐basic interactions in tungstate melts based on tungsten electroplating out of them

“…In the systems (3,6-10), 84.8; 38.3; 26.4; 30.9; 92.0 and 60.2% of emitted heat respectively spends on electrical job, Table 1. The thermal coefficient of voltages of systems (2,4,5,11) and (12), is positive, Table 1. According to this in the electrical job transforms not only all heat which emits during the functioning of the reaction but also part of heat which absorbs from outer environment.…”

“…Meanwhile the acidity of oxygenic ionic melt can be determined by concentration of O 2– ions or by the value of its logarithmic index pO = –lg [O 2– ]. The influence of acidic‐basic balances on electrochemistry kinetics in halogenide‐oxide melts were studied in .…”