Xianglong MENG
,
Wei CAI
,
K.T.Lau
,
L.M.Zhou
,
Liancheng ZHAO
,
null
,
null
材料科学技术（英）
The use of Ni-rich TiNiHf alloys as high temperature shape memory alloys (SMAs) through aging has been presented. For Ni-rich Ti80-xNixHf20 alloys, their phase transformation temperatures are averagely increased more than 100 K by aging at 823 K for 2 h. Especially for the alloys with Ni-content of 50.4 at. pct and 50.6 at. pct, their martensitic transformation start temperatures (Ms) are more than 473 K after aging. TEM observation confirmed that some fine particles precipitate from the matrix during aging. The aged Ni-rich TiNiHf SMAs show the better thermal stability of phase transformation temperatures than the solutiontreated TiNiHf alloys. The fine particles precipitated during aging should be responsible for the increase of phase transformation temperatures and its high stability.
关键词:
TiNiHf alloy
,
null
,
null
,
null
Jinghua YIN
,
Meicheng LI
,
Yufeng ZHENG
,
Zhong WANG
,
Wei CAI
,
Peilin WANG
,
Peilin WANG
材料科学技术（英）
The effect of annealing temperature on the formation of the PtSi phase. distribution of silicides and the surface morphologies of silicides films is investigated by XPS. AFM. It is shown that the phase sequences of the films change from Pt-Pt2Si-PtSi-Si to Pt+Pt2Si+PtSi-PtSi-Si or Pt+Pt2Si+PtSi-PtSi-st with an increase of annealing temperature and the reason for the formation of mixed layers is discussed.
关键词:
Xin GAO
,
Yufeng ZHENG
,
Wei CAI
,
Su ZHANG
,
Liancheng ZHAO
材料科学技术（英）
The microstructure, phase transformation, compression property and strain recovery characteristics of equiatomic TaRu super high temperature shape memory alloy have been studied by optical microscope, XRD, DTA, compression tests and TEM observations. When cooling the alloy specimen from high temperature to the room temperature, (parent phase)→ (interphase)→ (martensite) two-step phase transformations occur. The microstructure at room temperature show regularly arranged band morphology, with the monoclinic crystal structure. The twinning relationship between the martensite bands is determined to be (101) of Type I. Reorientation and coalescence of the martensite bands inside the variant happened during compression at room temperature. The → reversible transformation contributes mainly the shape memory effect, with the maximum completely recovery strain of 2%.
关键词:
TaRu alloy
,
null
,
null
,
null
Liming WANG
,
Yufeng ZHENG
,
Wei CAI
,
Xianglong MENG
,
Liancheng ZHAO
材料科学技术（英）
The effect of thermal cycling under loading on martensitic transformation and two-way shape memory effect was investigated for Ti-49.8 at, pet Ni alloy. It is shown that M-s, and M-f temperature increase with increasing the number of cycles, while A(s) and A(f) temperature decrease during thermal cycling. The total strain at and permanent strain epsilon (p) increase with increasing applied stress and number of cycles. The two-way shape memory effect can be improved by proper thermal cycling training under loading, while excessively high applied stress results in the deterioration of TWSME. The reason for the changes in martensitic transformation characteristics and two-way shape memory effect during thermal cycling under loading is discussed based on the analysis of microstructure by TEM observations.
关键词:
Xianglong MENG
,
Wei CAI
,
K.T.LAU
,
L.M.ZHOU
,
Liancheng ZHAO
材料科学技术（英）
The Effect of the thermal cycling training under constant strain on the two-way shape memory effect (TWSME) in a Ti36Ni49Hf15 high temperature shape memory alloy (SMA) has been investigated by bending tests. The results indicated that the training procedure is beneficial to get the better TWSME. The two-way shape memory strain increases with increasing the training strain. And it decreases with increasing the training temperature. The TWSME obtained in the present alloy shows poorer stability compared with that obtained in the TiNi alloys.
关键词:
TiNiHf alloy
,
null
,
null
,
null
Liming WANG
,
Xianglong MENG
,
Wei CAI
,
Liancheng ZHAO
材料科学技术（英）
A two-way shape memory effect (TWSM E) in the Ti46.3Ni44.7Nb9 alloy has been systematically investigated by means of bending test and transmission electron microscopy (TEM) observations. Based on the analysis of the microstructure after training, the mechanism of TWSME in the Ti46.3 Ni44.7Nb9 alloy has been discussed.
关键词:
Qingfu CHEN
,
Wei CAI
,
Liancheng ZHAO
材料科学技术（英）
The paper studied the relationship between microstructure and shape recovery characteristics by using colored microstructure analysis under polarized light on the thermomechanical cycled CuAINi single crystals. The two-way shape memory effect in quenched thin bar resulted from the preferential formation/extinction of martensite variant due to the internal quench stress, and the variant was formed at an angle of about 45 deg. with the tension direction ([001] of the beta phase). Initial thermomechanical cycling under relatively low stress single variant stress-induced martensite was formed at an angle of 45 deg. with the tension and its morphology was a lath of parallel twins. More than one group of variants were formed after several training cycles and such variants also caused tilting of some thermally formed accommodated martensite. By overheating the trained sample containing stabilized multi-variants of stress-induced martensite, very coarse martensite structure with a strong asymmetry was produced, which caused the reverse two-way shape memory effect.
关键词:
Jiehe SUI
,
Wei CAI
,
Liancheng ZHAO
材料科学技术（英）
A dense and well-adhered diamond-like carbon (DLC) coating was prepared on the nickel-titanium (NiTi) alloys by plasma immersion ion implantation and deposition (PIIID). Potentiodynamic polarization tests indicated the corrosion resistance of the NiTi alloys was markedly improved by the DLC coating. The Ni ions release of the NiTi alloys was effectively blocked by the DLC coating.
关键词:
NiTi alloys
,
null
,
null
