Influence of Ti Powder Characteristics on Combustion Synthesis of Porous NiTi Alloy

Porous NiTi shape memory alloy (SMA) is a novel biomedical material used for human hard tissue implant .The influence of elemental titanium powder characteristics such as powder morphology, particle size and specific surface area( SSA) on the minimal ignition temperature ,combustion temperature and final product of porous Ni-Ti SMA fabricated by combustion synthesis method was investigated in this paper by scanning electron microscopy (SEM) and laser diffraction.The preliminary data indicated that the titanium powder characteristics had a strong effect on combustion synthesis of porous NiTi SMA.     

NiTi形状记忆合金激光气体氮化层表面特征

为改善NiTi合金的表面性能，利用2kW连续波Nd：YAG对NiTi合金进行激光气体氮化处理。采用SEM、TEM、XRD、XPS和纳米压痕研究了氮化层的显微组织及表面特征．结果表明：激光气体氮化可以在NiTi合金表面制备连续、无裂纹、厚度为2μm的TiN表面层，该表面层中基本不合有Ni元素且具有很高的硬度，其纳米压痕硬度为29．28GPa．     

NiTi形状记忆合金螺钉的研制及医学应用

成功地研制了一种新型NiTi形状记忆合金螺钉并已临床应用了150例,经3年多考核,未发现骨不连及股骨头缺血坏死现象。     

钙磷层对NiTi形状记忆合金与骨组织结合特性的影响

用化学处理的方法 ,在NiTi合金表面生成钙磷 (Ca P)层 ,再将试样植入日本大耳兔的股骨中考察其生物相容性。试验结果表明 :经表面处理的试样和骨组织结合良好 ,并能传导新生骨的形成 ,表明经处理后有良好的生物相容性。而未经处理的试样 ,在实验范围内 ,没有观察到成骨细胞的存在及新生骨的形成     

磁控溅射制备纳米Ni-Ti薄膜工艺研究

为了得到高质量的纳米薄膜，对直流磁控溅射法制备Ni-Ti薄膜工艺进行了研究。采用单晶硅和玻璃两种基体材料，并在不同的基体温度、晶化温度、溅射功率等条件下制备薄膜。之后对薄膜进行了XRD，SEM分析。分析结果表明：薄膜成分、厚度、表面形貌、致密度与溅射功率、基体温度、晶化温度、基体材料密切相关。并根据实验结果给出优化的纳米Ni-Ti薄膜制备工艺。     

Microdefects and electron densities in NiTi shape memory alloys studied by positron annihilation

1Introduction NiTi alloys are the most successful shape memory alloys as a result of their combination of good functional properties and excellent mechanical strength[1,2].The thermal and mechanical shape memory behavior in these alloys is dependent upon …     

Design of a Medical Non‐Linear Drilling Device: The Influence of Twist and Wear on the Fatigue Behaviour of NiTi Wires Subjected to Bending Rotation

This paper considers fundamental and experimental aspects associated with the engineering design of a medical, non‐linear drilling device which exploits shape memory pseudoelasticity of NiTi wires. For this application it is important that the NiTi wires have a good fatigue resistance. This is why the present authors have previously determined the influence of various parameters on cyclic life, crack growth and stress state of pseudoelastic wires subjected to bending rotation fatigue. The actual drilling device has to withstand twist in addition to bending rotation because the free rotation is constrained by friction between the drill head and the bone material. In addition, friction between the wire and a NiTi guiding tube results in wear and this may well promote fatigue crack nucleation. In this paper, we explain the function of the medical drill. We then report results on the effect of the additional parameters (1) twist and (2) wear on the fatigue life of thin pseudoelastic NiTi wires. We finally discuss the implications of our experimental results for the design process of the medical drilling device.     

Influence of compression aging on phase transition temperatures in single crystalline Ni‐rich NiTi shape memory alloys

The present paper considers the phase transition behavior of a single crystal Ni‐rich NiTi alloy which was compression aged to produce one single family of Ni₄Ti₃ precipitates. The single crystal material was produced in a two stage process. Polycrystalline material was first melted under an inert atmosphere and remelted when single crystals were produced. Compression aging treatments in <111>‐orientation were carried out in order to suppress all but one family of Ni₄Ti₃‐precipitates which nucleate and grow on {111}‐planes of the B2 matrix. The objective of this study is to investigate the influence of Ni₄Ti₃‐precipitates on the martensitic transformation behavior. It was previously shown that grain boundaries provide heterogeneous nucleation sites for the formation of Ni₄Ti₃; this results in heterogeneous microstructures which undergo multiple step martensitic transformations. Single crystals avoid grain boundaries and the present study aims at clarifying how homogeneously precipitated particles affect martensitic transformations.     

预变形和时效对NiTi合金相变的影响

对Ti-50．8at％Ni形状记忆合金丝施加不同的预变形，随后在不同的温度时效，研究了预变形、时效温度与NiTi形状记忆合金的相变特性之间的关系。结果表明，预变形和时效对NiTi形状记忆舍金的相变特性有着显著的影响，可促使NiTi合金发生R相变，使NiTi形状记忆合金在较窄的温度区间内发生B2-R-B19’三种相变，为进一步研究NiTi形状记忆合金的性能提供了方便。     

Fabrication and characterization of NiTi shape memory alloy synthesized by Ni electroless plating of titanium powder

In this work NiTi shape memory alloy was fabricated from mixed elemental powders, Ni plated titanium powder and Ni heated/plated titanium powder by Ar-sintering. Electroless plating process was utilized to fabricate Ni plated titanium powder. For this purpose titanium powder was plated in an electroless Ni bath for 225?min and hydrazine hydrate was used as a reductant to deposit pure nickel on the titanium particles. Ni plated titanium powder was heat treated under an argon atmosphere at 1000?°C to prepare Ni heated/plated titanium powder. Finally, the three sample powders were pressed by CIP followed by sintering at 980?°C for 8?h to manufacture NiTi shape memory alloy. The prepared powders, as well as sintered samples, were characterized by scanning electronic microscopy (SEM), energy dispersive spectrometer analysis (EDS), X-ray fluorescence (XRF), X-ray diffraction (XRD) and differential scanning calorimetric (DSC). The results indicated the presence of NiTi phase and also non-transformable phases (NiTi₂ and Ni₃Ti) in the heated/plated Ti powder and sintered samples. NiTi compound was dominated phase in the heated/plated sintered sample. All three sintered samples, as well as heated/plated powder, showed one-step phase transformation (B2???B19′).