钛含量对新型钨钛合金微观组织及力学性能的影响_英文_王星

off timely along the adiabatic shear band during the penetrating process. However, the application of DU has raised serious, long-term environmental and health concerns. Precious work in promoting the “self-sharpening” ability of WHAs mainly focused on adding rare metal elements, such as yttrium, lanthanum and cerium, to refine the tungsten grain and enhance the susceptivity to adiabatic shear band, but the efforts were not satisfactory. In the present study, titanium substituted for rare metal elements was added in the tungsten alloy because of its low thermal conductivity to improve the susceptivity to adiabatic shear band in new WHA. This paper mainly researched the effect of titanium content on the microstructure and mechanical properties of new WHAs.
ARTICLE
Effect of Titanium Content on the Microstructure and Mechanical Propertiy
Wang Xing, Duan Dongping, Guo Yunshu
Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
Rare Metal Materials and Engineering Volume 42, Issue 6, June 2013 Online English edition of the Chinese language journal
Cite this article as: Rare Metal Materials and Engineering, 2013, 42(6): 1108-1112.
Abstract: Tungsten heavy alloys (WHAs) with four different titanium contents (0.5%, 1.0%, 1.5%, 2.0%, wt.%) were prepared by powder metallurgy. The influence of titanium content on the microstructure and mechanical properties under high strain rates were investigated. The results show that the titanium particles disperse in the matrix with different morphology and the main effective element is the diameter of the titanium particles. There are lots of micro holes in the titanium particles when the diameter of titanium particles is larger than 20 μm. The titanium particles do not dissolve in the matrix during the sintering process and the interfaces between titanium and tungsten, titanium and matrix are good. The results of Hopkinson Striker Bar indicate that the dynamic compressive strength is highest when the content of titanium is 0.5% and the strength has little change as the content of titanium increases from 1.0% to 2.0% under 3700 s-1 strain rate. In the WHA with 2.0% titanium content, the adiabatic shear banding (ASB) is the main deformation mode and the titanium in the ASB is fragile, the temperature of thermal softening area is higher than that of the traditional WHAs because of the existence of titanium particles. The addition of titanium in the WHAs improves the adiabatic shear banding susceptivity. Key words: powder metallurgy; titanium content; tungsten heavy alloy; dynamic mechanical property; adiabatic shear banding
Tungsten heavy alloys (WHAs) have drawn much attention in recent years with regard to their potential application as an anti-armor material due to good mechanical properties. WHAs, bi-phased composites made up of tungsten (bcc) particles and binder phase nickel, iron (fcc), are usually fabricated through a powder metallurgy process[1-6]. WHAs are promising substitutes for deplete uranium (DU) in the application of kinetic energy penetrators for their high densities (16~18.5 g/cm3) and prominent mechanical properties. However, besides high density and high toughness, materials used for penetrators demand high “self-sharpening” ability which ensures the head of penetrators keeping an acuate sharp during the penetrating process and therefore reduces the diameter of the penetration tunnel. Kinetic energy penetrators made of WHAs usually form “mush-room heads”, resulting in poorer penetration performance compared with DU alloys due to their good susceptivity to adiabatic shear band (ASB) during the penetrating process, which makes deformed materials fall
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Experiment
Powder metallurgy was employed to prepare the new WHAs with four titanium contents. The compositions of the four WHAs were 92.5% tungsten, 4.9% nickel, 2.1% iron and
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Wang Xing et al. / Rare Metal Materials and Engineering, 2013, 42(6): 1108-1112
0.5% titanium, 92.0% tungsten, 4.9% nickel, 2.1% iron and 1.0% titanium, 91.5% tungsten, 4.9% nickel, 2.1% iron and 1.5% titanium, 91.0% tungsten, 4.9% nickel, 2.1% iron and 2.0% titanium respectively. The tungsten powder (purity 99.9%, average particle size 3.5 μm), nickel powder (purity 99.9%, average particle size 27.5 μm), iron powder (purity 99.9%, average particles size 37.5 μm), and titanium powder (purity 99.6%, average particle size 42.4 μm) were mixed by a “V” type mixer for 24 h. The well-mixed powder mixture was cold-iso-statically pressed under 200 MPa. The compact was pre-sintered at 1100 °C for 1 h in a hydrogen furnace and finally sintered at 1480 °C for 1.5 h. At last it was vacuum annealed at 1200 °C for 5 h. Uniaxial dynamic compression tests were carried out using Split Hopkinson Pressure Bar at 3700 s-1 strain rate. For the experimental investigation of compressive strength, circular specimens with overall dimensions of Φ5 mm×5 mm were machined. At least four specimens were tested for each experimental condition. The specimens were sectioned along the compressing axis and the sectioned surfaces were polished to a mirror finish in order to observe the localized flow and analyze the evolutionary mechanism of adiabatic shear bands. The microstructure and section surface of new tungsten alloy were observed by field emission scanning electron microscopy (FESEM).