The uniaxial tensile deformation behavior of a sandwich-like structural TiNb-NiTi composite was investigated by uniaxial tensile test and in situ high-energy synchrotron X-ray diffraction(SXRD).It is found that below ...The uniaxial tensile deformation behavior of a sandwich-like structural TiNb-NiTi composite was investigated by uniaxial tensile test and in situ high-energy synchrotron X-ray diffraction(SXRD).It is found that below 1.2%macroscopic strains,the elastic deformations of the B2,β,B19'andα"phases take place in the TiNbNiTi composite.During the subsequent loading,theβ→α"and B2→B19'stress-induced martensitic transformations(SIMTs)occur within the macroscopic strains of 0.5%-4.2%and the macroscopic strains of 0.7%-6.2%,respectively.At the macroscopic strain of about 4.2%,the outer TiNb layer of the TiNb-NiTi composite experiences a partial fracture,as proved by the disappearance of(040)_(α")and a sudden jump in the(110)_(B19')d-spacing caused by load transfer.With further uniaxial tensile deformation,the TiNbNiTi composite finally fractures at a strain of~6.2%.Our results might provide some valuable information for understanding the deformation behavior of novel sandwich-like structural shape memory composites in more depth.展开更多
In the present study,a body-centered-cubic(BCC)structured Nb/TiNb multilayer nanocomposite with high yield strength,which comprises a soft TiNb matrix and reinforced Nb nanowires,was designed and fabricated with the a...In the present study,a body-centered-cubic(BCC)structured Nb/TiNb multilayer nanocomposite with high yield strength,which comprises a soft TiNb matrix and reinforced Nb nanowires,was designed and fabricated with the aim of elucidating the strengthening mechanism of Nb/TiNb multilayer nanocomposite by scanning electron microscope,transmission electron microscopy and in situ synchrotron X-ray diffraction.It is observed that the Nb/TiNb nanocomposite possesses a high yield strength of~640 MPa,significantly exceeding that of the conventional single-phaseβ-type Ti alloys.Further experimental results indicate that as plastic deformation commenced in the TiNb matrix of Nb/TiNb nanocomposite,load transfer from the soft TiNb matrix into the reinforced Nb nanowires occurred,allowing for a high load-bearing stress contribution and a significant strength enhancement of Nb/TiNb nanocomposite.Meanwhile,the embedded Nb nanowires can effectively impede the propagation of dislocation in TiNb matrix,further strengthening the present nanocomposite.These findings elucidate the strengthening mechanism of Nb/TiNb nanocomposite through the above two combinations,providing a basis for the design and development of the high-strength composites with a single-phase BCC structure for biomedical applications.展开更多
The micromechanical behavior of a recently developed TiNb/NiTi composite during a pre-straining process was investigated to broaden the understanding of deformation mechanisms of the martensitic-transforming composite...The micromechanical behavior of a recently developed TiNb/NiTi composite during a pre-straining process was investigated to broaden the understanding of deformation mechanisms of the martensitic-transforming composites.It was found that during loading,besides inherent elastic elongation,the TiNb/NiTi composite also experienced two different categories of stress-induced martensitic transformations(SIMTs,including B2→B19’andβ→α")and slight plastic deformation.Upon the following unloading,this composite recovered elastically,and underwent simultaneously a fully reversibleα"→βSIMT as well as a partially reversible B19’→B2 SIMT.It was the incomplete B19’→B2 SIMT and the permanent plastic deformation that led to the~4.6%macroscopic residual strain after unloading.In the entire loading-unloading procedure,the growth and shrinkage of(001)compound twins in B19’martensite also contributed to the large nearlinear-elastic deformation of the present composite.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.51771082 and51775251)the Six Talent Peaks Project in Jiangsu Province(No.2019-XCL-113)+1 种基金Zhenjiang Science&Technology Program(No.GY2020001)the Project of Faculty of Agricultural Equipment of Jiangsu University(No.NZXB20200101)。
文摘The uniaxial tensile deformation behavior of a sandwich-like structural TiNb-NiTi composite was investigated by uniaxial tensile test and in situ high-energy synchrotron X-ray diffraction(SXRD).It is found that below 1.2%macroscopic strains,the elastic deformations of the B2,β,B19'andα"phases take place in the TiNbNiTi composite.During the subsequent loading,theβ→α"and B2→B19'stress-induced martensitic transformations(SIMTs)occur within the macroscopic strains of 0.5%-4.2%and the macroscopic strains of 0.7%-6.2%,respectively.At the macroscopic strain of about 4.2%,the outer TiNb layer of the TiNb-NiTi composite experiences a partial fracture,as proved by the disappearance of(040)_(α")and a sudden jump in the(110)_(B19')d-spacing caused by load transfer.With further uniaxial tensile deformation,the TiNbNiTi composite finally fractures at a strain of~6.2%.Our results might provide some valuable information for understanding the deformation behavior of novel sandwich-like structural shape memory composites in more depth.
基金supported by the National Natural Science Foundation of China(Nos.51771082,51971009 and 52175410)Zhenjiang Science and Technology Program(No.GY2020001)+2 种基金the Six Talent Peaks Project in Jiangsu Province(No.2019-XCL-113)the Project of Faculty of Agricultural Equipment of Jiangsu University(No.NZXB20200101)Advanced Photon Source,a US Department of Energy(DOE)Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No.DE-AC02-06CH11357.
文摘In the present study,a body-centered-cubic(BCC)structured Nb/TiNb multilayer nanocomposite with high yield strength,which comprises a soft TiNb matrix and reinforced Nb nanowires,was designed and fabricated with the aim of elucidating the strengthening mechanism of Nb/TiNb multilayer nanocomposite by scanning electron microscope,transmission electron microscopy and in situ synchrotron X-ray diffraction.It is observed that the Nb/TiNb nanocomposite possesses a high yield strength of~640 MPa,significantly exceeding that of the conventional single-phaseβ-type Ti alloys.Further experimental results indicate that as plastic deformation commenced in the TiNb matrix of Nb/TiNb nanocomposite,load transfer from the soft TiNb matrix into the reinforced Nb nanowires occurred,allowing for a high load-bearing stress contribution and a significant strength enhancement of Nb/TiNb nanocomposite.Meanwhile,the embedded Nb nanowires can effectively impede the propagation of dislocation in TiNb matrix,further strengthening the present nanocomposite.These findings elucidate the strengthening mechanism of Nb/TiNb nanocomposite through the above two combinations,providing a basis for the design and development of the high-strength composites with a single-phase BCC structure for biomedical applications.
基金financially supported by the National Natural Science Foundation of China(No.52175410)the Six Talent Peaks Project in Jiangsu Province(No.2019-XCL-113)+1 种基金Zhenjiang Science&Technology Program(No.GY2020001)the Project of Faculty of Agricultural Equipment of Jiangsu University(No.NZXB20200101)。
文摘The micromechanical behavior of a recently developed TiNb/NiTi composite during a pre-straining process was investigated to broaden the understanding of deformation mechanisms of the martensitic-transforming composites.It was found that during loading,besides inherent elastic elongation,the TiNb/NiTi composite also experienced two different categories of stress-induced martensitic transformations(SIMTs,including B2→B19’andβ→α")and slight plastic deformation.Upon the following unloading,this composite recovered elastically,and underwent simultaneously a fully reversibleα"→βSIMT as well as a partially reversible B19’→B2 SIMT.It was the incomplete B19’→B2 SIMT and the permanent plastic deformation that led to the~4.6%macroscopic residual strain after unloading.In the entire loading-unloading procedure,the growth and shrinkage of(001)compound twins in B19’martensite also contributed to the large nearlinear-elastic deformation of the present composite.
