Effects of Tungsten and Boron Contents on Crystallization Temperature and Microhardness of Tungsten Based Metallic Glasses

Abstract

Effects of tungsten and boron contents on the thermal properties and microhardness of W-Fe-B metallic glass system were studied. Thin foils, with thicknesses of 20 and 100 lm, of the alloys were produced by piston and anvil method in an arc furnace. The structures of the foils were investigated by X-ray diffraction. Thermal stabilities of the alloys were examined by using differential scanning calorimetry. 20-lm-thick foils of all the alloys were determined to be fully amorphous, but crystalline phases were detected in the 100-lm-thick foils. It was found that crystallization temperatures of the alloys are between 1060 and 1177 K. Tungsten and boron content increases improve the crystallization temperature and microhardness of the alloys significantly, but deteriorate the glass forming ability of the alloys. It was also observed that for constant Fe content, increasing tungsten content to the level higher than that of boron content does not result in any further improvement in crystallization temperature, but improves glass forming ability significantly. The alloy containing highest total amount of tungsten and boron, W 35 Fe 35 B 30 , has the highest crystallization temperature, 1177 K, and microhardness, 1634 HV.

Preparation and Characterization of Amorphous W–B–C Alloy and Solid Solutions of C in Tungsten Borides

“…8d and 9d that most of diffraction peaks appear at diffraction angles of the WB and three weak peaks at diffraction angles of W 2 B 5 , but no diffraction peak of W, C and C-related compounds is observed. These results indicate that the W reacted with the amorphous W-B-C(I) completely at 1200°C to form WB and a small amount of W 2 B 5 , and C cannot incorporate into WB and W 2 B 5 , which are similar to some literatures reported previously [3,12]. Figure 10a-d shows XRD patterns of the 80 h-milled mixture (1:5) unannealed and annealed at 900, 950 and 1200°C, respectively.…”

“…Using Eq. (1), the solubility of B and C in the W is estimated to be 0.4%, which is the same as the solubility of B in the W. These results are different from those reported previously [12], where B or C cannot incorporate into W at high temperature ([ 1600°C). This difference may be that the W(B,C) solid solution comes from crystallization of amorphous W-B-C(I) alloy at low temperature, which leads to a result that a trace amount of B and/or C remain in W. Resembling to Fig.…”

“…In the past 30 years, various approaches, including solid-state reactions, molten salt electrolysis, chemical vapor deposition, mechanical alloying (MA), and self-propagating hightemperature synthesis (SHS) [3][4][5][6][7][8][9][10][11], were used for preparing various types of tungsten borides by using amorphous boron (B) or B 4 C as B source and W, WC or WO 2 as W source. Up to now, six types of tungsten borides, WB, W 2 B, W 2 B 5 , WB 2 , WB 4 and WB 12 , have been obtained and an equilibrium thermodynamic W-B phase diagram has been established in high-temperature range ([ 1800°C) [12]. Among these tungsten borides, WB 4 is a kind of superhard material (32-46 GPa) [13][14][15]; its hardness is much lower than that of other materials: For example, WB and W 2 B 5 only have hardness of 25-27 GPa.…”

Effect of W Addition on Fe-P-C-B Soft-Magnetic Amorphous Alloy

“…This shows that the content of W significantly affects the thermostability of the amorphous phase. Considering the Δ H mix (enthalpy of mixing) of W-P, W-C, and W-B are −46.5 kJ/mol, −60 kJ/mol, and −31 kJ/mol, respectively [ 26 ], it is not surprising because the W atom can strengthen the cohesive energy through the formation of W-metalloid bonds within Fe-based amorphous alloys, which reduce the diffusion ability of metalloid elements in the amorphous structure and impede the precipitation of α-Fe from the amorphous phase [ 27 ].…”

Synthesis of Co-based Metallic Glass Coatings by Pneumatic Squeezing Method

“…Kaplama işlemi pnömatik sıkıştırma basıncı (5 bar) ile hareket eden iki piston arasında gerçekleştirilmiştir. Sıkıştırma işlemi esnasında uygun miktardaki master alaşım parçası koruyucu atmosfer koşulları altında 150 A'de ergitilmiş ve ergitme işlemi ile eşzamanlı olarak iki piston arasında ~400 m/s hız ile sıkıştırılmıştır (Öztürk and Hitit, 2015 [Yazici, Z.O, 2016]. Kalınlığı <0,5 mm olan galvanizli plakanın ince olması nedeniyle fazlaca ısınmakta ve ısı transfer problemine neden olarak arayüzeyin kristallenmesine neden olduğu düşünülmektedir.…”