The formation and thermal stabilities of Cu46.25Zr46.25xAl7.5Erx (x=0 to 8) bulk metallic glasses (BMGs) were investigated. The addition of a small amount of Er (2at%) for replacing Zr effectively improves the glass-forming ability of Cu46.25Zr46.25Al7.5 alloy, and the glassy rod with a diameter of at least 12 mm can be formed. The glass transition temperature (Tg), temperature interval of su- percooled liquid region △Tx (=Tx-Tg), and reduced glass transition temperature Trg (=Tg/Tl) of Cu46.25Zr44.25Al7.5Er2 glassy alloy are 699 K, 62 K and 0.607, respectively.
Junying Fu, Hua Men, Shujie Pang, Chaoli Ma, and Tao Zhang Department of Materials Science and Engineering, Behang University, Beijing 100083, China
Mg65Cu20Zn5Y9Zr1 bulk metallic glass matrix composite with a diameter of 2 mm was produced by copper mold casting. Upon cooling the Mg65Cu20Zn5Y9Zr1 melt, Mg2Cu acicular crystalline phase precipitates uniformly with a size of about 20 μm long and 1 μm thick while the remaining melt undergoes glass transition. Room temperature compression tests revealed that the high fracture strength up to 830 MPa and the plastic strain of 2.4% before failure are obtained for the Mg-based bulk metallic glass matrix composite. The formation of the Mg2Cu phase was proposed to contribute to high strength and plastic deformation of the material.
Wei Tian, Shujie Pang, Hua Men, Chaoli Ma, and Tao Zhang Department of Materials Science and Engineering, Beihang University, Beijing 100083, China
Fe-based amorphous alloys with ductility were synthesized using the commercial cast iron QT50 (denoted as QT) with the combining minor addition of B and Al by single roller melt-spinning. The melt-spun (QT1-xBx)99Al1 (x is from 0.006wt% to 0.01wt%) amorphous alloys exhibit onset crystallization temperatures and Curie temperatures of 759-780 and 629-642 K respectively, and whi- ch increase with B content. The amorphous ribbons are ductile and can be bent 180° without breaking. With the increase in B content from 0.006wt% to 0.01wt%, the Vickers microhardness of the amorphous alloys increases from Hv 830 to Hv 1110. The effects of the additional B and Al elements on the glass forming ability and mechanical properties were also discussed.
Kun Tian, Shujie Pang, Hua Men, and Tao Zhang Department of Materials Science and Engineering, Beihang University, Beijing 100083, China
The heating processes of amorphous NixZr100-x(x=10, 16.7, 33.3) alloys were investigated with molecular dynamics simu- lations. The simulation results show that the crystallization of amorphous alloys during heating is controlled by the heating rate and the alloy’s composition. The slower heating rate depresses the crystallizing temperatures and the melting temperatures of the amor- phous alloys. Crystallization can be eliminated at rapid heating rates, the critical value of which decreases with increasing Ni content of the studied amorphous Ni-Zr alloys. Different crystalline structures formed during crystallizing depend on the heating rate, and the transition between crystalline structures was observed in the heating processes.
Quanwen Yang, Shujie Pang, and Tao Zhang Department of Materials Science and Engineering, Beihang University, Beijing 100083, China
The formation of bulk metallic glasses (BMGs) in ternary Cu-Zr-Ti system was investigated by a copper mold casting method. The nature of the amorphous phase was verified by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). It was demonstrated that the BMGs could be formed in a broad composition range in this system. Cu50Zr42.5Ti7.5, Cu60Zr27.5Ti12.5, Cu60Zr30Ti10 and Cu60Zr32.5Ti7.5 alloys exhibit strong glass-forming ability (GFA), and fully glassy rods of 5 mm in diameter can be obtained. In the center region of the ternary diagram, however, the GFA of the alloys was degraded due to the presence of Laves phase. The degradation of the GFA results from easy nucleation of the Laves phase in the undercooled liquid.
Hua Men, Junying Fu, Chaoli Ma, Shujie Pang, and Tao Zhang Department of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100083, China
