| With the highest elastic modulus?400GPa?,tungsten is an ideal reinforcement in composite materials.However,it`s very difficult to composite W with other metals due to its highest melting point about 3420?and reaction with most of the metals at high temperature.Though there are some composite materials with micron scale W particles,poor deformation ability to severe deformation processing.Recently,our group obtained W/NiTi composites with well severe deformation ability by smelting Ni4W,Ti,Ni.The W nanowire buried in the composites shows an elastic strain up to 3.4%.This paper aims to clarify the mechanism of W nanowires buried in the composites.The deformation behavior of W/NiTi composites were studied by the means of TEM in situ tensile deformation.Research results show that W nanowires in a diameter of 200 nm can show 4.3%of the largest elastic strain.And the generation of large elastic strain in W nanowires is closely linked to the martensitic phase transformation of NiTi matrix.After breaking,a large number of dislocation will appear near the fracture.The dislocation occurred inside W nanowires could across the interface of W and NiTi,but the dislocation occurred inside NiTi couldn`t.In addition,NiTi/Nb/W composite plate were also prepared by the method of accumulative roll-bonding with NiTi/Nb/W/Nb as a unit.Nb layer has played a very good buffer and adjust action in the composites to solve the poor deformation processing of W/NiTi composites made by ARB.And through drawing the plate,we obtained wires with 0.17mm diameter.The Nb nanowires and W nanowires show an elastic strain up to 2.29%and 1.2%respectively. |
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