Research On The Microstructure And Properties Of Multi-metal Composites Prepared By Accumulative Roll Bonding

Compared to particle-reinforced composites,the manufacturing process of multi-metal composites is relatively simple,and the performance of multi-metal composites can meet the requirements of industrial applications.With the advancement of technology,metal composites have developed from the bi-metal to the current multi-metal composites.At the same time,in the manufacturing process,different components can be designed according to actual application requirements,and the corresponding processing technology can be selected.However,it is difficult to bond multiple metals in the first pass.In this paper,the Ni/Ti/Nb,Ni/Ti/Al/Cu and Ni/Ti/Al/Nb composites were prepared by the accumulative roll bonding.According to different composites,different processes were developed to successfully prepare the three composites,and the microstructure and properties of the three composites were investigated.In addition,annealing experiments were conducted on the Ni/Ti/Al/Cu and Ni/Ti/Al/Nb composites,and the interface reactions and diffusion kinetics were studied.The Ni/Ti/Nb composite was successfully prepared by accumulative pack-roll bonding process at 500? for five cycles,and the reduction of each cycle was 67%.The Ni/Ti/Al/Cu and Ni/Ti/Al/Nb composites were produced by accumulative roll bonding at room temperature for eight passes.And then the Ni/Ti/Al/Cu and Ni/Ti/Al/Nb composites were annealed at 300?,350?,400?,450?,500?for 0.5 h,1 h,2 h,4 h respectively.The microstructure evolution and the interface diffusion after annealing were investigated by scanning electron microscope(SEM),energy dispersive spectrometer(EDS),X-ray diffraction(XRD),transmission electron microscope(TEM)and electron backscatter diffraction(EBSD).The interface diffusion kinetics during annealing was investigated combining the Arrhenius model.The mechanical properties of the composites were studied by tensile test and micro-hardness test.The results as follows:The Ni/Ti/Nb composite kept a layered structure during the five-cycle rolling process,and no intermetallics was formed at the interface.As the number of ARB process increased,the tensile strength and the micro-hardness of the composite increased significantly,and the elongation decreased.After 5 passes,the tensile strength of the composite reached 792.3 MPa,and the micro-hardness of Ni,Ti and Nb increased to 270.2,307.4 and 243.4 HV.For the Ni/Ti/Al/Cu composites,Ni,Ti,and Cu were homogeneously distributed in the Al matrix after 8 passes,and no intermetallics was formed at the interface.After eight passes,the average micro-hardness of Ni,Ti,Al,Cu improved from 157.9,161.3,23.8,59.3 HV to 284.3,254.4,60.4,162.2 HV,respectively.Additionally,the micro-hardness was linearly related to the actual equivalent strain.After eight passes,the tensile strength reached the maximum,which was 298.2 MPa.By observing the fracture surface of the composites,it is found that the fracture mode of the composites in the ARB process changes from interface separation to the formation and growth of dimples in the matrix.The Ni/Ti/Al/Cu composite of the fourth pass was annealed.For the Ni/Al interface,the NiAl3 was generated at the interface by annealing at 400?.And the mesophases generated at the interface by annealing at 450? and 500? were NiAl3 and Ni2Al3.For the Cu/Al interface,the CuAl2,Cu9Al4 and CuAl were generated at the interface by annealing at 350?,and CuAl2,CuAl and Cu3Al2 were generated at the interface by annealing at 400? and 450?.Additionally,CuAl2,CuAl,Cu3Al2 and Cu4Al3 were generated at the interface by annealing at 500?.For the Ti/Al interface,the mesophase is formed only at 500?,and the mesophase formed was TiAl3.The atomic diffusion at the interface in the composites conforms to the law of the Arrhenius equation.The activation energies of atomic diffusion at the Ni/Al,Cu/Al and Ti/Al interfaces are 16579,22983 and 25501 J·mol-1,respectively.For the Ni/Ti/Al/Nb composite produced by the ARB process,the dynamic recovery occurred in the Al matrix after the third pass,resulting in an increase of the HGAB fraction and the decrease of the dislocation density.Additionally,the increasing fraction of the HGABs was also contributed by shear bands.After the fourth pass,the Al exhibited a combination texture of rolling texture and shear texture.The rolling texture components were composed of Copper{112}<111>,Dillamore{4 4 11}<11 11 8>,S{123}<634>,and Brass{011}<211>,and the shear texture components were Rotated Cube {001}<110>and {111}//ND.The micro-hardness of Ni,Ti,Nb,and Al were improved in the ARB process and finally reached 226.4,246.3,187.2,and 44.2 HV,respectively.The Ni/Ti/Al/Nb composites after the first,the fourth and the eighth pass were annealed,and there were no intermetallic compound formed at the Nb/Al interface.The diffusion activation energies of the Nb/Al interface in the samples of the first,the fourth and the eighth pass were 14134,12316 and 10125 J·mol-1,respectively.Furthermore,the increase in rolling deformation can reduce the activation energy of interface diffusion.