Preparation Of Ti-base Metallic Glass Composites And Their Microstructures And Properties

Ti alloys are extensively used in many areas, such as biomedical, chemistry, aviation industry etc., due to their excellent corrosion behavior, low density, and high strength. In recent years, Ti-base bulk metallic glasses(BMGs) have been developed, which exhibit very high tensile strength of up to 2200MPa. However, the BMGs usually show very small plasticity due to the formation of highly localized shear bands under loading. So, we should investigate Ti-base BMGs with the aim to improve their plasticity.In this work, cast cylinders of Ti50Cu23Ni20Sn. Ti60Cu14N12Sn4ISIb10and TisoCttt40 Co5 bulk glass-forming alloys were prepared by copper-mold casting method, and their microstructures, phase constitutions, thermal stabilities and mechanical properties at room temperature were investigated by using X-Ray diffraction (XRD), DTA, scanning electron microscope(SEM) and transmission electron microscopy(TEM), etc.. The main results are as follows:l.The as-cast Ti50Cu23Ni2oSn cylinder contains dendritic hcp-Ti solid solution precipitations, as well as interdendritic glassy and Sn-rich and Culi2 crystalline phases. The Ti60Cu14Ni12Sn4Nb10 cylinder exhibits a microstructure with flower-like dendritic bcc-p-Tl solid solution precipitations and partially crystallized glassy matrix. While, the Ti5oCu4oNi2oCo5 cylinder contains bcc-J3-Ti solid solution precipitations and nanostructured matix.2. For as-cast TieoCuHNiSatNbio cylinder, the contents of Nb and Sn are much higher than that in matrix, which implies that the additions of Nb and Sn promote the formation of -Ti type dendtrites.3. The ultimate compression stress of the as-cast TieoCunNi12SajNbio cylinder is 1.71GPa ultimate stress with 11.3% plastic strain, and yielding occurs at 1.1 GPa. While, the ultimate compression stresses are 1.67MPa with 4.7% plastic strain for theas-cast Ti50Cu23Ni20Sn cylinder and 1.37MPa with 12.2% plastic strain for the as-cast Ti50Cu40Ni20Co5 cylinder respectively. The as-cast TieoCunNiuSniNbio cylinder exhibits superior comprehensive properties in comparison with the other two alloys.4. Deformation occurs partially through dislocation movement in dendrites, and partially through shear-banding mechanism in grassy or nanostructured matrices. The dendrites also act as obstacles restricting the excessive deformation by isolating the highly localized shear band in matrices. The deformation mechanisms may be attributed to the high ductility of the alloys.5. The strength and ductility of these alloys are strongly dependent on the volume fraction, size and shape of dendrites, as well as the microstructure of the matrix.