Superelastic-superplastic powder-metallurgy NiTi shape memory alloy made by meso-scale particles

细观颗粒超弹超塑性粉末冶金镍钛形状记忆合金

• 批准号: 07555478
• 负责人: HASHIMOTO Satoshi
• 金额: $ 0.19万
• 依托单位: KYOTO UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1995
• 资助国家: 日本
• 起止时间: 1995 至 1996
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07555478/
• 关键词: powder metallurgy; NiTi; superelasticity; shape mewary alloy; superplasticity; martenrite; Powder metallurgy; NiTi; super elasticity; shape memory alloy; super plasticity; martensite; fatigue; power metallurgy; Ni Ti; superelasticity; shap

This is the first report for the powder metallurgy of titanium-nickel shape memory alloy having both shape memory and mechanical strength comparable to the alloy made by casting and wire-drawing. The fatigue properties and mechanism of the fracture were also investigated.The process for the powder metallurgy is as follows ; Titanium-Nickel alloy powder was produced by Plasma Rotation Electrode Process. The method was used to suppress the impurity contamination during atomizing process. The powder with an average diameter of 0.287mm was hot-pressed by Hot Isosotatic Pressing, and a compact having a relative density of 99.7% was obtained. The martensitic transformation temperature was identical to that of the ingot used for making the powder.Monotonic tensile test of the compact showed the shape memory strain and also the superelastic strain of 7% : the stress-strain behavior was almost identical to the cast alloy. However, it fractured by the deformation above 7%, which is much smaller than in cast alloys.In the case of cyclic tensile deformation, the initiation and propergation of crack of the compact happenned by smaller tensile strain. The fracture occurred by the cleavage of the powder surfaces. By in-situ observation of the surface relief of tensile specimens, it is found that the stress-induced martensitic transformation develops by an inhomogenerous manner, which resembles the propagation of Ruders Band. The crack nucleated within the bands. Therefore, the fatigue life of the compact did not depend explicitely on the amplitude of tensile deformation.

这是首次报道粉末冶金钛镍形状记忆合金，其形状记忆和机械强度可与铸造和拉丝制成的合金相媲美。还研究了疲劳性能和断裂机理。粉末冶金工艺如下；采用等离子旋转电极工艺生产钛镍合金粉末。该方法用于抑制雾化过程中的杂质污染。将平均直径为0.287mm的粉末通过热等静压进行热压，得到相对密度为99.7%的成形体。马氏体转变温度与用于制造粉末的铸锭的温度相同。压坯的单调拉伸测试显示出形状记忆应变以及7%的超弹性应变：应力-应变行为与铸造合金几乎相同。然而，它在7%以上的变形时断裂，这比铸造合金小得多。在循环拉伸变形的情况下，压坯裂纹的萌生和扩展是在较小的拉伸应变下发生的。断裂是由于粉末表面的劈裂而发生的。通过对拉伸试样表面浮雕的原位观察，发现应力诱导马氏体相变以不均匀的方式发展，类似于鲁德斯带的传播。裂纹在带内成核。因此，压坯的疲劳寿命并不明确取决于拉伸变形的幅度。

项目成果

S.Onaka: "Retardation of Intergranular Fracture at Intermediate Temperatures by a Boundary node in a Cu-9at.%Pl Alloy Tricrystals" Acta Metall Maters. 43. 307-311 (1995)

S.Onaka:%20"延迟%20of%20粒间%20断裂%20at%20Intermediate%20温度%20by%20a%20边界%20node%20in%20a%20Cu-9at.%Pl%20合金%20Tricrystals"%20Acta%20Metall%20Maters

S.Hashimoto: "Fatigue Crack Initiation and Propagation in Compact Tension Copper Single Crystals" Zeitschrift fur Metallkde.87. 128-134 (1996)

S.Hashimoto：“致密张力铜单晶中的疲劳裂纹萌生和扩展”Zeitschrift Fur Metallkde.87。

S.Onaka: "Retardation of Intergranular Fracture at Intermediate Temperature by a Boundary node in a Cu-9at.70Hl Alloy Tricrystal" Acta Metall.Mater.43. 307-311 (1995)

S.Onaka：“Cu-9at.70Hl 合金三晶中的边界节点在中温下延缓晶间断裂”Acta Metall.Mater.43。

S.Onaka: "Determination of the Aspect Ratio of a spheroidal Perticle by Steres Observation" Materials Characterization. 34. 167-172 (1995)

S.Onaka：“通过立体观察确定球形颗粒的纵横比”材料表征。

S.Onaka: "Determination of the Aspect Ratio of a Spheroidal Particle by Stereo Observation" Materials Characterization. 34. 167-172 (1995)

S.Onaka：“通过立体观察确定球形颗粒的纵横比”材料表征。