Properties Of Tungsten Heavy Alloys Research Articles

Effect of oxide dispersoids addition on mechanical properties of tungsten heavy alloy fabricated by mechanical alloying process

The microstructures and mechanical properties of mechanically alloyed oxide dispersion strengthened tungsten heavy alloys were investigated. Elemental powders of tungsten (W), nickel (Ni), iron (Fe) and partially stabilized zirconia (PSZ) were mechanically alloyed by a planetary mill. Mechanically alloyed powders were consolidated by liquid phase sintering at temperature ranged 1465–1485 °C for 1 h in hydrogen atmosphere to obtain full densification. The W grain size decreases with increasing PSZ content. The oxide dispersoids were dispersed both within W grains and W/W and W/matrix interfaces. The yield strength of oxide dispersion strengthened tungsten heavy alloy was not dependent on PSZ content but dependent on microstructural factor, while the elongation decreases with increasing PSZ content. However, the high temperature yield strength increases with increasing content of PSZ dispersoid and the PSZ dispersoids act as the strengthening agent at high temperature deformation.

Heat Treatment Behavior of Tungsten Heavy Alloy

This paper focuses on the variations of static and dynamic properties of tungsten heavy alloy with heat treatment. The matrix phase of 93W-4.9Ni-2.1Fe (weight percent) has been penetrated into W/W grain boundaries during a cyclic heat treatment which consists of repeated isothermal holdings at 1150 °C and water quenching between them. By applying the cyclic heat treatment, the impact energy of tungsten heavy alloy is increased about three times from 57 to 170 J. When the tungsten heavy alloy is cyclically heat treated at 1150 °C and then re-sintered at 1485 °C, W/matrix interface is changed from round to undulated shape. The irregularity of the interface is increased with increasing the number of heat treatment cycles. From the measurement of the residual stress of W grains by X-ray diffraction, it is found that the irregularity of the interface is closely related with strain energy stemmed from the difference of thermal expansion coefficient between W particles and matrix phase. From dynamic ballistic test, it is found that the tungsten heavy alloy with undulated W grains forms many narrow fracture bands which are preferential for the self sharpening effect, thus, for the improvement of the penetration performance.

Effect of matrix alloy and cold swaging on micro-tensile properties of tungsten heavy alloys

The tensile properties of two types of tungsten heavy alloys, W–5.6% Ni–1.4% Fe and W–4.7% Ni–2.2% Co, were investigated as a function of matrix alloy (Ni–Fe vs. Ni–Co) and specimen orientation with respect to the cold swaging axis. Orientation dependent rod properties were measured using a micro-tensile testing unit developed at LLNL. Tungsten particles were slightly oblong in the swage direction in both alloys and particle–particle bonding was also apparent in both alloys. In the W–Ni–Fe alloy separation between W particles and the Ni–Fe matrix was observed, as well as Ni–Fe matrix cracking. The W–Ni–Co alloy showed no evidence of separation between W and the matrix alloy or Ni–Co matrix cracking. Differences in the matrix material condition appear to manifest themselves in the observed tensile properties and fracture surfaces. The ultimate tensile strength and elongation at failure values of the W–Ni–Co alloy were larger than those of the W–Ni–Fe alloy.

Effects of mechanical alloying on structure and properties of tungsten heavy alloy

Effects of mechanical alloying on structure and properties of tungsten heavy alloy

Effects of powder mixing technique and tungsten powder size on the properties of tungsten heavy alloys

Properties of tungsten heavy alloys are known to vary with process parameters such as sintering temperature, time and atmosphere. In this study, tensile properties of the 92.5W–5.25Ni–2.25Fe and 90W–7Ni–3Fe heavy alloys were found to be influenced by powder mixing technique and tungsten powder size. For a given tungsten powder grade (mean particle size 10.5 or 3.4 μm), attritor milled alloys exhibited better tensile properties than those of the turbula-mixed alloys. Compared to finer grade, coarser tungsten powder generally resulted in alloys with higher ductility when turbula mixer was used. Overall, the alloys prepared from turbula mixed powders containing finer tungsten grade showed the lowest tensile properties. Metallographic analyses revealed that these alloys failed in more brittle fashion as a result of a high degree of contiguity of tungsten grains, which was inherited from powder mixing step.

Effect of particle size and shape on dynamic torsional properties of tungsten heavy alloys: S.Lee et al. (University of Science and Technology, Pohang, Korea.) Metall. Mater. Trans. A, vol 30A, no 5, 1999, 1261–1273

Effect of particle size and shape on dynamic torsional properties of tungsten heavy alloys: S.Lee et al. (University of Science and Technology, Pohang, Korea.) Metall. Mater. Trans. A, vol 30A, no 5, 1999, 1261–1273

Dynamic torsional properties of tungsten heavy alloys : K.J. Park et al. (Poongsan Corp, Kyungju, Korea.) J. Korean Inst. of Metals, vol 34, no 4, 1996, 447–456. (In Korean.)

Dynamic torsional properties of tungsten heavy alloys : K.J. Park et al. (Poongsan Corp, Kyungju, Korea.) J. Korean Inst. of Metals, vol 34, no 4, 1996, 447–456. (In Korean.)

Testing of properties of tungsten heavy alloys: J.Bucki et al. (University of Technology, Warsaw, Poland.)

Testing of properties of tungsten heavy alloys: J.Bucki et al. (University of Technology, Warsaw, Poland.)

Process engineering and properties of tungsten heavy alloys: Z. Ludynski, W. Novak (ORBIT, Warsaw, Poland.) Metal. Proszkow, vol 28, no 3/4, 1995, 24–28. (In Polish.)

Process engineering and properties of tungsten heavy alloys: Z. Ludynski, W. Novak (ORBIT, Warsaw, Poland.) Metal. Proszkow, vol 28, no 3/4, 1995, 24–28. (In Polish.)

Processing and properties of tungsten heavy alloys with nickel-aluminium-iron matrix : S. Guha et al (Materials and Electrochemical Research Corp, Tucson, Arizona, USA.) Materials and Manuf. Process., vol 9, no 6, 1994, 1163–1187

Processing and properties of tungsten heavy alloys with nickel-aluminium-iron matrix : S. Guha et al (Materials and Electrochemical Research Corp, Tucson, Arizona, USA.) Materials and Manuf. Process., vol 9, no 6, 1994, 1163–1187

Aging induced changes in mechanical properties of tungsten heavy alloys : P. Doepker, L.J. Cuddy (Pennsylvania State University, Pennsylvania, USA)

Aging induced changes in mechanical properties of tungsten heavy alloys : P. Doepker, L.J. Cuddy (Pennsylvania State University, Pennsylvania, USA)

Enhancement of properties of tungsten heavy alloys by microstructural modifications : R.M. German et al (Pennsylvania State University, Pennsylvania, USA)

Enhancement of properties of tungsten heavy alloys by microstructural modifications : R.M. German et al (Pennsylvania State University, Pennsylvania, USA)

Microstructural changes in liquid phase sintering tungsten-nickel alloys: S. Kohara (Science University of Tokyo, Tokyo, Japan).

The intrinsic brittleness of tungsten limits the improvement on the comprehensive mechanical properties of tungsten alloys. Starting from the perspective of solid solution toughening, this study innovatively used tungsten-tantalum particles instead of tungsten particles as the sintered core to prepare 90(W-Ta)-Ni-Fe alloy. Tantalum forms a BCC solid solution with tungsten in the process of high-energy ball milling. During the vacuum sintering process, tantalum precipitated and reacted with the matrix to form acicular phase. This precipitation process reduces the liquid phase sintering temperature of the tungsten alloy and refine the tungsten particles. The microstructure of the sintered alloy is composed of tungsten particles, matrix phase, intermediate phase, acicular precipitated phase and oxides. The solid solution of tantalum increases the hardness and reduces the modulus of the tungsten particles. The hardness and modulus of the matrix phase are increased due to the influence of the acicular precipitation phase. These findings indicate that the solid solution of tantalum has the potential to improve the comprehensive mechanical properties of tungsten heavy alloys.

Improvement of mechanical properties of tungsten heavy alloys: D.Y. Yoon et al (Korea Advanced Inst. of Science and Technology, Daejon, Korea)

Improvement of mechanical properties of tungsten heavy alloys: D.Y. Yoon et al (Korea Advanced Inst. of Science and Technology, Daejon, Korea)

Effects of processing on microstructure and properties of tungsten heavy alloys: E.Y. Gutmanas et al (Technion, Haifa, Israel)

Effects of processing on microstructure and properties of tungsten heavy alloys: E.Y. Gutmanas et al (Technion, Haifa, Israel)

Dynamic compressive properties of tungsten heavy alloys with varying grain sizes: A. Bose et al (Southwest Research Inst, USA).

Dynamic compressive properties of tungsten heavy alloys with varying grain sizes: A. Bose et al (Southwest Research Inst, USA).

Effect of binder composition on structure and properties of tungsten heavy alloys: E-P. Kim at al (agency for Defence Materials Research, Daejon, Korea), J Korean Inst of Metals, Vol 30, No 8, 1992, 963–971. (In Korean)

Nickel was electrodeposited from dilute aqueous solutions of nickel chloride, containing PW12O403− ions. It was shown that improvement in the overpotential (η) and in the exchange current density (io) of the hydrogen evolution reaction (h.e.r.) on the electrodes depends on the concentration of PW12O403− of the deposition bath. The h.e.r. electrocatalytic activity of the electrodeposits was then analysed and related to their chemical composition. The results show that some active electrocatalysts are produced when combinations of nickel-tungsten (Ni-W) are formed. The influence of the PW12O403− concentration in the electrode deposition electrolyte on the electrocatalytic properties of these deposits for the hydrogen evolution reaction (h.e.r.) was investigated. The best electrocatalytic properties for the h.e.r. are obtained with electrodes electrodeposited with 2 g l−1 of PW12O403−. The kinetic parameters for the h.e.r. in 3 M KOH were deduced for temperatures ranging from 298 to 353 K.

Effects of cold work and aging on mechanical properties of tungsten heavy alloys: H.S. Song et al (Agency for Defence Development, Daejon, Korea), J Korean Inst of Metals, Vol 30, No 3, 1992, 262–269, (In Korean)

Effects of cold work and aging on mechanical properties of tungsten heavy alloys: H.S. Song et al (Agency for Defence Development, Daejon, Korea), J Korean Inst of Metals, Vol 30, No 3, 1992, 262–269, (In Korean)

Effects of second aging treatment on mechanical properties of tungsten heavy alloys

Effects of second aging treatment on mechanical properties of tungsten heavy alloys

Effects of nickel:iron ratio on mechanical properties of tungsten heavy alloys : T. Kaneko, J. Japan Soc Powder and Powder Metallurgy, Vol 38, No 4, 1991, 540-2-547. In Japanese

Effects of nickel:iron ratio on mechanical properties of tungsten heavy alloys : T. Kaneko, J. Japan Soc Powder and Powder Metallurgy, Vol 38, No 4, 1991, 540-2-547. In Japanese