Formation, Thermal Stability and Mechanical Properties of Cu-Zr and Cu-Hf Binary Glassy Alloy Rods

Abstract

Glassy alloy rods with diameters up to 1.5 mm exhibiting a large supercooled liquid region before crystallization and high mechanical strength were formed in Cu-Zr and Cu-Hf binary alloy systems by the copper mold casting method. The large supercooled liquid region exceeding 40 K was obtained in the composition range of 30 to 70 at%Zr and 35 to 60 at%Hf. The largest value of the supercooled liquid region defined by the difference between glass transition temperature (T g ) and crystallization temperature (T x ), ÁT x ð¼ T x À T g ), was 58 K for Cu 60 Zr 40 and 59 K for Cu 55 Hf 45 . The reduced glass transition temperature (T g =T l ) of the two alloys was 0.61 and 0.59, respectively. The alloys with large ÁT x above 50 K were formed into a bulk glassy alloy form with diameters up to 1.5 mm by copper mold casting. The Cu 60 Zr 40 , Cu 45 Zr 55 , Cu 60 Hf 40 and Cu 55 Hf 45 glassy alloy rods exhibited high fracture strength of 1920, 1880, 2245 and 2260 MPa, respectively, Young's modulus of 107, 102, 120 and 121 GPa, respectively, a nearly constant elastic elongation of about 1.9% and plastic elongation up to 2.2%. The formation of these binary glassy alloy rods can be interpreted in the framework of the concept of the formation of the unique glassy structure consisting mainly of icosahedral atomic configuration as similar to that for special multi-component alloys with the three component rules.

Ultrahigh Strength and High Electrical Conductivity Characteristics of Cu-Zr Alloy Wires with Nanoscale Duplex Fibrous Structure

“…On the other hand, the highest strength of Cu-based alloys has been reported to be 900 to 1500 MPa for Cu-Be base alloys subjected to an optimum age-hardening treatment 1,2) and 600 to 1500 MPa for Cu-M (M ¼ Nb or Ag) alloy wires produced by heavy cold drawing, [3][4][5][6] though disordered glassy alloys in Cu-based alloy system exhibit much higher tensile fracture strength of 2000 to 2500 MPa. [7][8][9][10] On the other hand, the electrical conductivity is about 24 to 50%IACS for the age-hardened Cu-Be alloys 1,2) and 50 to 90%IACS for the Cu-M alloy wires. [3][4][5][6] Considering that the highest strength of crystalline metallic materials has been obtained for cold-rolled Fe-C alloy (piano wire) with a fibrous structure consisting of -Fe ferrite and Fe 3 C cementite carbide, 11,12) it is expected that higher strength characteristics in Cu-based alloys are obtained in Cu-based alloys with the similar fibrous mixed structure.…”

Study on crystallization kinetics of binary alloys through model colloidal mixtures

“…This compositional complexity makes it extremely difficult for different atoms to rearrange their spatial positions so that they are frozen directly into a disordered glassy structure upon cooling. Recently, binary BMG forming alloys have also been developed in a few alloy families [6][7][8][9][10][11][12][13][14], and their GFA is found to be very sensitive to the minor change of chemical composition [15,16]. These further confuse the criterions of GFA in metallic alloys.…”

“…The size ratio (q) of small to large particles in the present binary colloid system is 0.69, which is quite similar to the atomic size ratio of Cu-Hf binary alloy (0.6971). It is interesting to find that there are two best glass-forming compositions reported up to now, Cu 55 Hf 45 [9] and Cu 65 Hf 35 [7,8] with the corresponding mixing ratios of 1.22 and 1.86, respectively. The agreement between the colloid mixtures results and the experiment data of binary bulk metallic glasses supports the present experimental design, and gives a direct evidence for the validity of topological factor in determining the glass-forming ability in binary metal liquid.…”

“…r small /r large Cu-Zr [10][11][12] 0.7039 Cu-Hf [7][8][9] 0.6971 Ni-Nb [13] 0.7525 Ca-Al [14] 0.6082 that q ranges from 0.55 to 0.80. Here, we use a binary colloid system to simulate the situation of binary BMGs with large particle (d = 2.9 m) and smaller particles (d = 2.0 m).…”

Structural origin of the pinpoint-composition effect on the glass-forming ability in the NiNb alloy system

“…However, recently, MGs with relatively high GFA were successfully prepared in binary alloy systems, such as the CuZr 8 and the NiNb 9 systems. These simple alloys have attracted intense interest because they have unique properties [10][11][12] and they are the representative models for studying glass-forming mechanisms. [13][14][15][16] Further more, studying the binary MGs may enhance our understanding of the formation of their corresponding multicomponent MGs.…”