The Research On The Preparation Of Ti Based Amorphous And Nanocrystalline Alloy

Ti-based amorphous alloys are extensively used in many areas,such as aerospace,chemistry,biomedical etc,due to excellent corrosion behavior,low density and biocompatibility.However,the amorphous alloys exhibit small plasticity and strength,which limits their application prospect.Therefore,it is the key to solve how to prepare a Ti-based amorphous/nanocrystalline alloy of the higher strength and the better plasticity.In the paper,Ti_xNi_xCu_50-xZr_50-x?x=25,30,35,38,40,42,44?alloys 2mm in diameter were fabricated by arc-melting and cast into a copper mold.Using scanning electron microscopy,X-ray diffraction,transmission electron microscopy and electrochemical measurements analysis phase composition,analysis of milled powder morphology,mechanical properties and corrosion behavior.Next,the effects of Co and Nb addition on the GFA,mechanical properties and corrosion behavior of Ti₄₄Ni₄₄Cu₆Zr₆ alloy system were studied.And,the work was to determine the effect of cooling rate and volume fraction of the glassy phase on the mechanical properties of the Ti₄₄Ni₄₄Cu₄Zr₆Co₂,Ti₄₄Ni₄₄Cu₆Zr₆ alloys.The results show that the structure of Ti_x Ni_xCu_50-xZr_50-x?x=25,30,35,38,40,42,44?alloys 2 mm in diameter contain the glassy phase and the cp2 crystalline phase?nanocrystalline?.For Ti_xNi_xCu_50-x0-x Zr_50-x?x=38,40,42,44?alloy,transformation induced plasticity?TRIP?and superelasticity effects were found to exist.With the increase of Ti,the strength and plasticity of the alloys were improved,especially,the fracture strength and total strain of Ti₄₄Ni₄₄Cu₆Zr₆ alloy is 2750MPa and 27%.And,the corrosion resistance ability was improved in 0.5mol/L H₂SO₄,3.5%NaCl and1mol/L NaOH aqueous solutions.The addition of Co and Nb to the alloy leads to the increase in GFA mechanical properties and corrosion behavior.The cooling rate of Ti₄₄Ni₄₄Cu₄Zr₆Co₂,Ti₄₄Ni₄₄Cu₆Zr₆ 2mm in diameter were bigger than 4mm in diameter which leads to decrease in the volume fraction of the glassy phase,which do not contribute to martensitic transformation.Ti₂₅Ni₂₅Cu₂₅Zr₂₅ metallic glass composite was processed by cryogenic treatment at different times.The variation of mechanical properties and corrosion resistance of the amorphous composite samples before and after the cryogenic treatment were studied.The results show that before cryogenic 3 days,the mico-hardness and the compression fracture strength of the alloys were improved.But when the cryogenic time reached to 5 days,the rising tendency of the strength and hardness of the alloys became flat.In 0.5mol/L H₂SO₄,?3.5%NaCl and 1mol/L NaOH aqueous solutions,Ti₂₅Ni₂₅Cu₂₅Zr₂₅ alloy of cryogentic treatment lead to the deterioration of the corrosion resistance ability.