Cu—Zn—Al形状记忆合金速动记忆元件的研制

1.引言近年来,对NjTj基和Cu基形状记忆合金的形状记忆效应和记忆元件的设计已有很多研究,这些合金的形状记忆效应与合金的热弹性马氏体转变有关。一般热弹性马氏体相变的相变温区较大,用它制成的热敏元     

亚稳Ti-27Nb合金单晶的变形行为

<正>亚稳β型钛合金由β相向α″相转变的应力诱发马氏体相变及其逆相变的过程中表现出超弹性,使其作为新的无镍形状记忆合金,前景备受期待。针对亚稳β型钛合金的马氏体相变和形状记忆超弹性特性已开展了多项研究。为明确Ti-27Nb合金(原子分数)的应力诱发α″马氏体相变过程中的塑性变形行为,东京工业大学T.Masaki对Ti-27Nb合金单晶进行了研究。首先采用光学浮动区域熔融法制备了Ti-27Nb     

FeMnSi形状记忆合金的研究

本文研究了FeMnSi合金中热形成ε马氏体、α马氏体以及位错和残余应力等对形状记忆效应(SME)的影响,讨论了温轧试样中由于轧制织构引起的SME各向异性问题,同时还研究了测量形状记忆合金(SMA)相变温度的音频共振法.     

Cu Zn Al形状记忆合金的研制和特性研究

形状记忆合金是一种新颖的功能材料,功能材料的研制是当今新材料开发的重要课题之一。自60年代初美国海军武器实验室的Beuhler等人发现近等原子Ni—Ti合金具有形状记忆效应(SME)以来,已有30多年时间,在这段时间内,形状记忆合金(SMA)及其相关的理论—热弹性马氏体相变理论几乎成     

一种新型Ti-Ni-Ce记忆合金的研制

本文通过透射电子显微镜（TEM）、差热扫描量热仪（DSC）等实验手段研究了在Ti-Ni二元合金中添加Ce后所形成的Ni48Ti49Ce3合金的微观组织和形状记忆效应。研究结果表明，合金在室温的组织存在〈011〉Ⅱ型和〈011〉Ⅰ型孪晶马氏体，Ce的添加使得〈011〉Ⅱ型孪晶马氏体的孪晶晶带变窄，合金的相变温度与二元合金相比明显提高，且具有很好的单程和双程形状记忆效应。     

Cu—Zn—Al记忆合金在双相状态下的形状记忆行为

本文系统地研究了在α+β两相区进行淬火处理的Cu-Zn-Al形状记忆合金的组织特点及形状记忆效应的变化规律。研究结果表明,两相区淬火可有效地调整合金的相变温度M_s、M_f、A_s和A_f。两相区淬火虽使合金的组织为α+β_1两相,但沿晶界分布和存在于晶内的少量α相并不破坏β_1相自身的热弹性马氏体转变。尽管α相的存在导致合金形状记忆恢复率的下降,但适量的α相仍能保证合金具有稳定的记忆恢复率,而且双向记忆性能稳定。     

不同工艺处理对Ni_(50.6)Ti_(49.4)合金相变及形状记忆效应的影响

本文系统地研究了时效、热循环等对Ni_(50.6)Ti_(49.4)合金相变及形状记忆效应的影响。结果表明,马氏体相变和R相变的开始点M_S和TR_s均随合金时效时间的延长而升高到一定值。热循环使淬火后不经其它处理的样品的M_3s降低,而TR_s不变。经过充分时效处理的样品,其M_sM、TR_s在循环过程中保持稳定。通过时效、冷加工、淬火后热循环处理的样品,均能使该合金的R相变与马氏体相变分离。但当采用后两种方法处理时,这两个相变仍相距较近。时效则能使二者相距较远,而且R相变的热滞较小,M_s、TR_s稳定。实验证实,仅在p(?)R相变范围内,虽有较好的单程形状记忆效应,但难以训练出显著的双向记忆效应。     

Ti-Ni形状记忆合金的疲劳性能

Ti- Ni形状记忆合金 (SMA)具有形状记忆效应和超弹性 ,其特性源于热弹性马氏体的形成和回复过程 ,相变过程的诱发需要温度或载荷变化。SMA要经历多次热应力或外加载荷循环作用 ,疲劳性能非常重要 ,其主要影响因素如下 :(1)合金马氏体相变开始温度 (Ms)。Ms不同导致合金相变过程和内部组织形态不同 ,疲劳寿命也不同。调整 Ni- Ti合金中 Ni含量 ,制备了 Ms 分别为 - 12 0℃ ,- 30℃ ,7.5℃和 70℃的合金。在室温下进行恒应变控制的疲劳试验。S- N曲线表明 :在应变相同的条件下 ,Ms 为 7.5℃的试样疲劳寿命最长 ,- 30℃和 70℃的居中 ,-…     

热循环对粉末冶金Cu-14Al-4Ni马氏体相变点的影响

粉末冶金方法可成功地制取 Cu-14Al-4Ni(wt%)形状记忆合金。热循环使得粉末冶金法制得的 Cu-14Al-4Ni 形状记忆合金热弹性马氏体相变温度升高,最后趋于稳定。淬火速率越大,热循环过程中热弹性马氏体相变的稳定性越差。同样的淬火速率,热循环上限温度越高,随热循环次数增加相变温度变化越大。粉末冶金方法制取的本合金经空冷后有较好的热循环稳定性。本文提出了用应力弛豫假说来解释热循环对马氏体相变温度的影响。     

热处理工艺对NiTi形状记忆合金马氏体相变的影响

对成分（at）为Ti－51．28％Ni合金的相变过程用电阻、金相法进行了研究．发现该合金加热过程中发生M→R＋M→B2转变，冷却时则有M→R＋M→B2转变．并用电阻－温度曲线测定了不同热处理工艺条件下合金的相变温度，讨论了固溶时效处理制度对马氏体相变及R相变的影响，也讨论了提高合金形状记忆效应稳定性的各种方式，结果表明，“高温固溶，中温时效”是有利于该合金马氏体相变的最佳热处理工艺．也是提高其形状记忆效应的有效途径。     

Influence of aluminium and iron contents on the transformation temperatures of Cu-Al-Fe shape memory alloys

Copper based shape memory alloys have received much focus in recent times because of their good ductility, ease of production and processing and low cost. Earlier investigations have shown that ductility and other mechanical properties of the Cu-Al based shape memory alloys can significantly be improved by adding ternary elements such as Ni and Mn. While Cu-Al-Ni shape memory alloys have better thermal stability and higher operating temperatures, their practical applications are limited because of their poor workability. Cu-Al-Mn shape memory alloys on the other hand, have good ductility and workability, but their operating temperatures are lower. A similar approach is followed in Ni-Al alloys to overcome their brittleness by the addition of Fe. There is paucity of literature on the role of ternary addition of Fe to Cu-Al shape memory alloys. In the present work, therefore, the effect of aluminium and iron on the transformation temperatures has been studied. As the aluminium content increases the transformation temperatures decrease, while the ternary addition of Fe increases the transformation temperatures. The results are presented and discussed in detail in the paper.     

Ti-V-Al轻质记忆合金的研究进展

Ti-V-Al合金基于热弹性马氏体相变而呈现出形状记忆效应。同时,Ti-V-Al合金不仅呈现出良好的冷热加工性能,还具有较低的密度,这可满足当今航空航天领域对轻量化制造的需求。文中主要综述国内外研究学者在Ti-V-Al轻质记忆合金研究方面的重要工作和进展,其中重点阐述了Ti-V-Al轻质记忆合金热循环稳定性、力学性能与功能特性方面的研究。最后,简单阐述了Ti-V-Al轻质记忆合金功能特性的演化规律与机制,并对后续Ti-V-Al轻质记忆合金的发展方向进行了展望。      

Ni55Mn25Ga18Ti2高温形状记忆合金的热循环稳定性

选择双相韧化的Ni?Mn?Ga?Ti高温形状记忆合金为研究对象。制备了淬火态Ni₅₅Mn₂₅Ga₁₈Ti₂高温形状记忆合金,并对其在室温至480 ℃之间进行高达500次的相变热循环,获得了5, 10, 50, 100和500次热循环态样品。采用X射线衍射、扫描电镜、能谱仪、同步热分析仪及室温压缩等实验方法,研究了淬火态和热循环态合金样品的微观组织、相变行为、力学及记忆性能,进而分析其热循环稳定性。研究结果表明:经500次循环后,Ni₅₅Mn₂₅Ga₁₈Ti₂合金相结构和显微组织未发生明显变化,均为由非调制四方结构的板条马氏体相和面心立方富Ni的γ相组成的双相结构;随着循环次数增加,马氏体相变温度几乎不变,逆马氏体相变温度和相变滞后在循环5次后趋于稳定;抗压强度及压缩变形率波动幅度较小;形状记忆性能下降,但形状记忆应变仍保持在1.4%以上;Ni₅₅Mn₂₅Ga₁₈Ti₂高温形状记忆合金显示出良好的热循环稳定性。      

Phase Transformation Behaviors and Effects of Terbium in Polycrystalline Ni-Mn-Ga Magnetic Shape Memory Alloys

The phase transformation behaviors of two kinds of magnetic shape memory alloys NisoMn25 x Ga25-x and Ni50 Mn29Ga21-x Tbx were studied. When the composition of Ni in these alloys was constant, increasing Mn and reducing Ga contents make martensitic transformation temperatures rise obviously. Simultaneously, thermal hysteresis of phase transformation reduce but Curie temperature una|ters. When terbium was added, phase transformation temperature went up further and Curie temperature kept constant. The alloys still show strong ferromagnetism and properties of thermoelastic martensite phase transformation.     

碳含量对Fe-15Mn-4.5Si-10Cr-5Ni-C系形状记忆合金性能的影响机制

 为通过调控碳含量获得形状记忆性能优异的铁基形状记忆合金,研究了3种不同碳含量对固溶时效态Fe-15Mn-4.5Si-10Cr-5Ni-C系形状记忆合金微观组织、力学性能及形状记忆效应的影响。结果表明,固溶时效态Fe-15Mn-4.5Si-10Cr-5Ni-(0.05~0.2)C合金的形状记忆效应随碳含量的增加呈现先增后减的趋势。这是由于一方面,随着碳含量的增加,碳原子的间隙固溶强化和第二相碳化物的沉淀析出强化提高奥氏体母相强度,抑制不可逆塑性变形的发生,有利于材料在受力时发生应力诱发奥氏体γ转变为ε马氏体(γ→ε),从而提高形状记忆效应。另一方面,全固溶温度随碳含量的增加而升高。由于全固溶温度的升高,固溶处理后得到的相对粗大的奥氏体晶粒造成奥氏体母相强度的降低。同时,随着碳含量的增加导致ε马氏体相变温度(M_εs)的降低,应力诱发相变过程受到抑制,不利于形状记忆效应。在不同影响机制的相互作用下,碳质量分数为0.091 8%固溶时效态试验合金的形状记忆性能最优。     

增材制造NiTi合金研究进展

NiTi作为一种形状记忆合金,具有优异的形状记忆效应、超弹性、耐腐蚀性、生物相容性,在生物医用、航空航天、微机电等领域均有着广泛的应用.增材制造(additive manufacturing,AM)技术作为一种新兴的加工方式,能够提高NiTi合金加工效率,并扩展NiTi合金应用领域.本文介绍了近年来国内外增材制造NiT...     

Thermal arrest memory effect

The course of the martensitic transformation is affected by strain fields in the untransformed parent phase, One of the consequences of this NiTi shape memory alloys is the “Thermal Arrest Memory Effect” (TAME), where the martensite to parent phase transformation “remembers” the temperature of arrest in the previous thermal cycle. From the results of the calorimetric investigations in this study, it is deduced that the TAME is the result of locked-in transformation strain energy in the self-accomodating martensitic microstructure. Thus it is found that on account of the large difference in the degree of self-accomodation achieved in the martensitic microstructures, TAME is observed to be significant in NiTi and not in CuAnAl shape memory alloys.     

Load and sliding velocity effect in dry sliding wear behavior of CuZnAl shape memory alloys

The wear behavior of shape memory alloys is linked to the thermoelastic martensitic transformation. Due to this transformation, these alloys have the ability to absorb a high amount of energy before undergoing plastic deformation and subsequent fractures caused by wear. In this study, the effect of sliding velocity and load on the dry wear behavior of CuZnAl alloys has been characterized. Weight loss as a function of the M_s transformation temperature at different sliding velocities and loads was studied for the different alloys. The weight loss and friction coefficient of the alloys as a function of load showed linear and exponential relationships, respectively; however, when considered versus applied sliding velocity, independently of which phase was present, they showed an exponential relation and no direct relation, respectively.     

Effect of grain size on the observed pseudoelastic behavior of a Cu-Zn-Al shape memory alloy

The shape of stress-strain curves for a pseudoelastic copper-based shape memory alloy (SMA) has been found to depend strongly on the grain size-to-sample thickness ratio (gs/t). Previous investigators have attributed this effect to reduced grain constraint in coarse-grain samples. The present investigation further analyzes the grain constraint effect by modeling shape memory alloy stress-strain curves. The model results reveal that varying grain constraint can explain the observed grain size effect on stress-strain curves. Furthermore, detailed consideration of the Taylor factor equivalent for Cu-Zn-Al and NiTi shape memory alloys can explain the opposite curvature of polycrystal stress-strain curves for these two materials. Finally, several indices of grain constraint are analyzed for the Cu-Zn-Al alloy examined in the present investigation and for similar alloys used in previous studies. This evaluation reveals that both transformation modulus and transformation stress correlate with gs/t, and each can be used as an index of grain constraint.     

Effects of ternary additions on the thermoelastic martensitic transformation of NiAl

Nickel-rich β-NiAl alloys, which are potential materials for high-temperature shape-memory alloys, show a thermoelastic martensitic transformation, which produces their shape memory effect. However, the transformation to Ni₅Al₃ phase during heating of NiAl martensite can interrupt the reversible martensitic transformation; consequently, the shape memory effect in NiAl martensite might not appear after heating. The phase transformation process in binary Ni-(34 to 37)Al martensite was investigated by differential thermal analysis (DTA) method, and we found that the condition of reversible martensitic transformation was not the β → Ni₅Al₃ transformation, but rather the M → Ni₅Al₃ transformation occurring at 250 °C to 300 °C. Therefore, the transformation temperature of M → Ni₅Al₃ determined the highest operating temperature for the shape memory effect. For verifying the critical temperature, the phase transformation process was investigated for eight ternary Ni-33Al-X alloys (X=Cu, Co, Fe, Mn, Cr, Ti, Si, and Nb). Only Ti, Si, and Nb additions were found to be effective in dropping the M _s temperature, and they facilitated the shape memory effect in Ni-33Al-X alloys. In particular, the addition of Si and Nb raised the transformation temperature of M → Ni₅Al₃, a potentially beneficial effect for shape memory at higher temperatures. This article is based on a presentation made in the symposium entitled “Fundamentals of Structural Intermetallics,” presented at the 2002 TMS Annual Meeting, February 21–27, 2002, in Seattle, Washington, under the auspices of the ASM and TMS Joint Committee on Mechanical Behavior of Materials.