Study On Mechanical Properties Of Cu-Zr-based Amorphous Alloy

Amorphous alloy compared to crystalline materials exhibits many unique properties such as high strength, hardness, fracture toughness, good wear resistance and corrosion resistance. These excellent properties make amorphous alloy added the great application prospects in the field of national defense industry, aerospace equipment, biomedicine, electronic information. Cu-Zr-based bulk amorphous alloy has become the focus of common concern of domestic and overseas researchers with with its unique advantages of economic value. In this paper, the series of Cu-Zr-Al-Co, Cu-Zr-Al-Ti, Cu-Zr-Al-Y alloy was prepared to be the samples with a diameter of 3 mm through the cooling copper mold suction casting method. The bars were prepared to test these structural characteristics for X-ray diffractometer (XRD), and several mechanical properties at room temperature. The fracture morphology was observed by scanning electron microscope (SEM), and the deformation behavior and fracture mode of the alloy were ensured. The microstructure and chemical composition of the materials were analyzed by transmission electron microscope (TEM). The results obtained in this paper are as follows:(1) The XRD measurement was performed that the forming ability of Cu50-0.5xZr50-0.5xAl* at first did not changed significantly with the Al content increased from 2 to 4 at.%. However, when Al content was increased to 6 at.%, the amorphous alloy’s glass forming ability has been improved obviously. At the same time, CuZr (B191) phase and AlCu2Zr phase disappears, leaving only the crystal phase contained B2-CuZr martensite phase and CuZr (Cm) phase. The room temperature compressive test results show that the fracture strength of the alloy exhibits a trend of first increasing and then decreasing when the content of Al is gradually increasing. Among them, the highest breaking strength is Cu48Zr48Al4,which fracture strength can reach 1788.3～1908.6MPa.(2) The amorphous forming ability of Cu47Zr47Al6 is stronger than that of Cu48Zr48Al4, but the compressive strength of the former is less than that of the latter. The formation of crystalline phases in Cu48Zr48Al4 alloy and Cu47Zr47Al6 alloy was affected by the addition of a minor amount of Co element. When the amount of Co reaches 2 at.% or more (Cu48Zr48Al4)100-xCo(x = 2,4,6 at.%) alloy and (Cu47Zr47Al6)100-xCox(x= 2,4,6 at.%) alloy crystal phase only left B2-CuZr phase and AlCu2Zr phase, no amorphous matrix appear. The room temperature compression performance test results show that, the Co addition may be reduce the fracture strength of Cu48Zr48sAl4 alloy and Cu47Zr47Al6 alloy. And the more the amount of Co adds, the lower fracture strength is. In addition, it almost did not show any plastic behavior. The fracture strength of (Cu48Zr48Al4)100-xCox (x= 0,2,4,6 at.%) alloys was reduced from 1788.3 1908.6MPa to 1484.2～1507.2MPa. The fracture strength of (Cu47Zr47Al6)100-xCox(x= 0,2,4,6 at.%) alloys was reduced from 1545.6～1559.3MPa to 1320.7～1410.9MPa.(3) The addition of a certain amount of Ti can significantly improve the glass forming ability and the compressive strength of Cu-Zr-Al amorphous alloy at room temperature. When the addition amount of Ti was 2 at.%, the compressive property of the amorphous alloy was the highest. The fracture strength, the plasticity, the elastic modulus and the microhardness of (Cu47Zr47Al6)98Ti2 alloy is 1991MPa, near zero,35.8GPa and 585.2HV, respectively. (Cu47Zr47Al6)100-xTix (x= 0,2,4,6 at.%) alloys are amorphous alloy, the fracture form are brittle fracture, fracture surface of a typical vein-like pattern. Due to the addition of Ti matrix formed Al3Ti crystal structure, Al3Ti as hard particles dispersed in the amorphous matrix, improve the mechanical properties of amorphous alloys.(4) The XRD measurement was performed that the addition of Y element can improve the amorphous forming ability of the (Cu47Zr47Al6)100-xYx (x=0,1,2,3 at.%) alloy. With the increase of the content of Y, the micro structure of the amorphous alloy is turned to:amorphous matrix+ B2-CuZr phase+ CuZr martensitic phase â†' amorphous matrix+B2-CuZr phase â†' pure amorphous state. The compressive test results show that the addition of minor amounts of Y can significantly improve the compressive properties of Cu47Zr47Al6. The highest fracture strength of (Cu47Zr47Al6)97Y3 alloy increased by 20.0% which up to 1855.1MPa, compared without Y, the modulus of elasticity is 24.2GPa and the plastic deformation is 0.12%.