再结晶对Ni47Ti44Nb9形状记忆合金棒相变和织构的影响

利用光学显微镜（OM）,DSC和XRD,研究了直径19 mm Ni47Ti44Nb9热轧棒材再结晶对相变和织构的影响,为该合金棒的实际应用提供理论依据。结果表明：热轧棒从450℃开始发生明显再结晶;从850℃/90 min真空退火棒材的中心到边缘,再结晶晶粒尺寸减小,Ms降低,马氏体转变区间变窄,热滞增大;热轧棒中形成了较强的γ丝织构,600℃/90 min退火后,γ丝织构强度稍有下降,退火温度升到850℃,丝织构明显减弱,等密度线发生漫散,形成了新的织构组分,这有利于改善棒材径向方向的恢复应变。     

Factors Determining the Maximum Recovery Stress of the Ni47Ti44Nb9 Alloy During Constrained Heating

Metallurgical and Materials Transactions A - The maximum recovery stress is an essential parameter for evaluating the reliability of shape-memory alloys. In this study, the factors that determine...     

Ni47Ti44Nb9冷轧板材取向对拉伸和恢复性能的影响

利用x射线衍射仪(XRD)、金相显微镜(OM)、维氏硬度计和万能电子拉伸试验机,研究了Ni<,47>Ti<,44>Nb<,9>形状记忆合金冷轧板材中的B2相沿轧向(RD)和横向(TD)的织构,以及热处理对冷轧板材硬度、显微组织、拉伸性能和恢复应变的影响.结果表明:冷轧板材的织构主要由较强的{111}丝(即γ-丝)和较弱的{332}丝组成.沿轧向,强组分向γ-丝中的{111}<110>靠近,而沿横向,强组分靠近γ-丝中的{111}<112>;随淬火温度提高,冷轧板材的硬度缓慢下降,超过500℃后,硬度急剧下降,到700℃以后硬度基本不变;冷轧板材在550℃发生明显再结晶,700℃处理后再结晶晶粒发生长大;随淬火温度提高,沿轧向(RD)和横向(TD)的应力诱发马氏体相变临界应力(σ<,M>)和可恢复应变(ε<,r>)降低.低于550℃淬火板材,沿轧向的临界应力σ<,M>高于沿横向方向的,而沿横向的可恢复应变ε<,r>较高,高于550℃淬火,沿横向的临界应力σ<,M>提高,可恢复应变ε<,r>沿轧向和横向的数值接近.     

Ti和/或Nb对高温合金25Cr37Ni0.6Nb组织和力学性能的影响

研究了150 kg真空感应炉冶炼并轧成30 mm板的0.05C-25Cr-37Ni-0.6Nb(0.6Nb),0.05C-25Cr-37Ni-0.6Nb-0.6Ti(0.6Nb-0.6Ti)和0.05C-25Cr-37Ni-1.8Nb(1.8Nb)3组合金1160~1220℃ 1 h空冷固溶处理的组织和性能。结果表明,与0.6Nb合金相比加Ti的(0.6Nb-0.6Ti)合金的晶粒明显粗化,析出相主要为微米级Ti(CN),室温强度降低,760℃蠕变性能降低;增加Nb含量的1.8Nb合金的晶粒细化,析出相主要为纳米级Nb(CN),室温强度和蠕变性能没有明显变化。     

稀土铽对Ni-Mn-Ga磁性记忆合金力学性能的影响

研究了稀土Tb对Ni50Mn29Ga21磁性记忆合金抗弯强度和断裂行为的影响。结果表明:稀土Tb可以显著提高材料的抗弯强度,改变断口形貌。不含稀土试样弯曲断裂后其断口主要是晶界断裂。添加稀土后,随着稀土加入量的增多,断裂方式由以晶界断裂为主转为以解理断裂为主。此外,Tb的加入,明显细化了晶粒,同时使材料的含氧量降低。     

预应变对Ni50.2Ti49.8合金记忆特性的影响

研究了Ni50.2Ti49.8合金在5种不同预应变(1.96%,3.96%,5.88%,7.85%,9.96%)下的回复应变和逆相变温度;恒定预应变5.88%下,热机械循环对回复应变和逆相变温度的影响。结果表明:预应变使得逆相变温度升高,预应变越大逆相变温度越高。随着预应变的增加回复应变增加,预应变增加到一定程度时回复应变达到最大值,随后回复应变随预应变增加而减少。恒定预应变下热机械循环,随循环次数增加,逆相变温度下降,回复应变减少,随着循环次数进一步增加,逆相变温度和回复应变逐步达到稳定值。     

Effect of Thermomechanical Treatment on Functional Properties of Biodegradable Fe-30Mn-5Si Shape Memory Alloy

The structure, martensitic γ ↔ ε transformation temperatures, Young’s modulus, mechanical properties, and electrochemical behavior of Fe-30Mn-5Si (wt pct) biodegradable shape memory alloy subjected to various thermomechanical treatments (TMT) comprising hot rolling or cold rolling with post-deformation annealing were characterized by optical microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, differential scanning calorimetry, tensile testing, open circuit potential, and polarization curves measurements in Hanks’ solution, as compared to reference heat treatment. The optimum combination of mechanical properties (low Young’s modulus, high tensile strength, and appropriate ductility) for biomechanical compatibility was obtained after TMT with hot rolling at 600 and 800 °C due to the formation of favorable dynamically polygonized and recrystallized structures and decrease in the γ↔ε transformation starting temperature down to the human body temperature. The TMT did not show a significant effect on the corrosion rate as compared to the appropriate corrosion rate after the reference heat treatment. It is concluded that the TMT with hot rolling at 600 or 800 °C, which provides an optimum combination of the required corrosion rate in the simulation body fluid with high biomechanical compatibility, can be considered a promising treatment of Fe-30Mn-5Si biodegradable alloy for bone implants.

     

形状记忆合金相变应变的取向关系及其织构控制原理

形状记忆效应是基于马氏体相变及其逆转变,相变时母相与马氏体相之间存在严格的晶体学取向关系。根据唯象理论,相变织构是可以预估的。同样地对于相变应变也存在取向关系,通过多晶材料的织构分析也可以预估。铜基形状记忆合金沿<100>方向呈最大的相变延伸,通过适当的热机械处理可以获得沿同轧向成45°方向的最大强度的<100>织构取向分量,因而有最佳的记忆效应。     

加工及热处理对Ti5Zr6Mol5Nb钛合金组织和性能的影响

以新型近β型医用钛合金Ti-5Zr-6Mo-15Nb（TLE）铸锭为实验原料,通过开坯、锻造、轧制、热处理等多道工序制成板材和棒材。分析了不同加工工艺及热处理制度对合金组织与性能的影响。结果表明：TLE合金具有较高的强度、较低的弹性模量、优良的塑韧性与疲劳性能,冷热加工性能好;合金经过适当的固溶与时效处理后可获得良好的综合力学性能匹配,特别适合充当外科植入物材料使用。     

Mechanical Properties of TiTaHfNbZr High-Entropy Alloy Coatings Deposited on NiTi Shape Memory Alloy Substrates

TiTaHfNbZr high-entropy alloy (HEA) thin films with thicknesses of about 750 and 1500 nm were deposited on NiTi substrates by RF magnetron sputtering using TiTaHfNbZr equimolar targets. The thorough experimental analysis on microstructure and mechanical properties of deposited films revealed that the TiTaHfNbZr films exhibited amorphous and cauliflower-like structure, where grain size and surface roughness increased concomitant with film thickness. More importantly, the current findings demonstrate that the TiTaHfNbZr HEA films with mechanical properties of the same order as those of the NiTi substrate constitute promising biomedical coatings effective in preventing Ni release.     

Ti-Ni-Ce合金的相变行为及其形状记忆效应

通过示差扫描量热仪(DSC)等试验手段,系统分析了添加稀土元素Ce后所形成的Ti-Ni-Cex(x＝2 at%、3 at%、4 at%)系合金的相变行为和形状记忆效应,以及相变温度和相变潜热与稀土含量之间的关系.研究结果表明,相变温度(Ms,Mf,As,Af)受稀土含量的影响较大,总的趋势是先升高后下降,然后有稍微升高;而对相变潜热(马氏体相变潜热ΔHB2M、逆马氏体相变潜热ΔHMB2)的影响,则是随着稀土元素Ce含量的升高呈现上升的趋势;稀土的添加使Ti-Ni二元合金的相变滞后明显变窄,但与稀土的含量没有明显关系.研究发现,添加稀土后Ti-Ni形状记忆合金优良的形状记忆效应没有改变,而相变温度却有明显的提高.     

热机械处理对Ti3Al基合金板条组织形貌及室温拉伸性能的影响

研究了热机械处理（ＴＭＰ）对Ｔｉ３Ａｌ基合金Ｔｉ－２４Ａｌ－１４Ｎｂ－３Ｖ（原子分数％）板条组织的形貌及室温拉伸性能的影响，通过ＴＭＰ可获得各种各样的板条组织。Ｔｉ－２４Ａｌ－１４Ｎｂ－３Ｖ板条组织的最高断裂强度可达１２２５ＭＰａ，最大伸长率达８．５％，对板条形貌与室温拉伸性能的关系进行了分析，用ＳＥＭ观察了室温拉伸过程中的裂纹扩展情况，经ＴＥＭ观察发现，在缓冷样品中板用周边存在着一种α２＋Ｏ相的     

热机械循环对Ti49.8Ni50.2形状记忆合金相变行为的影响

研究了热机械循环对Ti49.8Ni50.2形状记忆合金的回复应变RS、应力诱发马氏体的临界应力σM以及马氏体相变温度Ms和Mf的影响.实验结果表明: Ti49.8Ni50.2在热机械循环冷却过程中始终发生应力诱发B2→B19′马氏体相变.RS在第一次和第二次循环中分别获得最大值和最小值, 随着循环的继续进行又逐渐增加.RS在达到第二个极大值后又开始逐步减小.σM随着循环次数增加而迅速下降.Ms和Mf在前10次循环中无明显变化, 随着循环的继续进而升高.循环500次后, RS, σM以及Ms和Mf均达到稳定状态.循环引入的位错结构被认为是造成以上变化的主要原因.     

镍钛形状记忆合金薄膜的相变温度和力学性能

利用直流磁控溅射法溅射沉积了NiTi形状记忆合金薄膜，对NiTi形状记忆合金薄膜进行晶化热处理以使其获得形状记忆效应。研究了550℃晶化热处理1h后Ti-48.2%Ni薄膜的相变温度和力学性能，研究结果表明，NiTi薄膜550℃晶化热处理1h后，升温过程中发生M→A的相变，而降温过程中则先发生A→R相变，再发生R→M的相变，薄膜的断裂强度随测试温度的升高而增大，残余应变随温度的升高而减小，当温度大于Af点时，表现为超弹性。     

铌含量对LF9合金性能的影响

 研究了不同Nb含量的LF9合金经固溶+二次时效处理后的力学性能。结果表明,随Nb含量增加,合金的室温和高温强度提高,塑性及韧性下降。经960 ℃固溶+二次时效后,合金中的主要强化相为η相,随着Nb含量增加,η相数量增多,形态由短片状变为长片层状。经1 020 ℃固溶+二次时效后,合金中的主要强化相为(γ′+γ″),随着Nb含量增加,η相形态从微量的颗粒状变为大量的短片状,对提高合金强度起到了重要作用。经(960~1 020 ℃)固溶+二次时效后,合金中(γ′+γ″)相的尺寸主要为10~100 nm。     

Effect of Thermomechanical Processing on Microstructure,Texture Evolution,and Mechanical Properties of Al-Mg-Si-Cu Alloys with Different Zn Contents

The effect of thermomechanical processing on microstructure, texture evolution, and mechanical properties of Al-Mg-Si-Cu alloys with different Zn contents was studied by mechanical properties, microstructure, and texture characterization in the present study. The results show that thermomechanical processing has a significant influence on the evolution of microstructure and texture and on the final mechanical properties, independently of Zn contents. Compared with the T4P-treated (first preaged at 353 K (80 °C) for 12 hours and then naturally aged for 14 days) sheets with high final cold rolling reduction, the T4P-treated sheets with low final cold rolling reduction possess almost identical strength and elongation and higher average r values. Compared with the intermediate annealed sheets with high final cold rolling reduction, the intermediate annealed sheets with low final cold rolling reduction contain a higher number of particles with a smaller size. After solution treatment, in contrast to the sheets with high final cold rolling reduction, the sheets with low final cold rolling reduction possess finer grain structure and tend to form a weaker recrystallization texture. The recrystallization texture may be affected by particle distribution, grain size, and final cold rolling texture. Finally, the visco-plastic self-consistent (VPSC) model was used to predict r values.

     

不同加工状态钛铌丝对其铆钉组织和性能的影响

研究了加工态丝材和退火态丝材所加工的Ti45Nb合金铆钉的组织及性能。冷拉拔加工态钛铌丝材抗拉强度为680 MPa,剪切强度为390 MPa,且塑性良好,延伸率A为20%,断面收缩率Z为80%,具有良好加工性能。加工态丝材经退火后,组织实现完全再结晶,抗拉强度降低至550 MPa,塑性有所提高,延伸率A达到30%。两种状态丝材经冷镦加工成铆钉后,与丝材相比,剪切强度均增高,这与冷镦加工造成加工硬化有关;而对铆钉进行退火后,剪切强度均降低,且加工态丝材镦制的铆钉的剪切性能一致性优于退火态丝材镦制的铆钉。     

Effect of Intermittent Overload Cycles on Thermomechanical Fatigue Life of NiTi Shape Memory Alloy Wire

Effect of intermittent overload cycles on fatigue behavior of NiTi shape memory alloy wire during thermomechanical cycling (TMC) has been evaluated. Results showed that fatigue life of NiTi is enhanced when the intermittent overload is above certain minimum level. An enhancement in fatigue life by ~50 pct is observed when the overload ratio is 2.0. Accumulation of plastic strain in the material under such TMC condition is found to be relatively high compared to that of TMC with no overload cycles.     

Microstructure and Mechanical Properties of Cryorolled Aluminum Alloy AA2219 in Different Thermomechanical Processing Conditions

Metallurgical and Materials Transactions A - In the present study, aluminum alloy AA2219-T87 bars were cryorolled to various amounts of deformation in two pre-deformation conditions: (1) without...