EFFECT OF COMPOSITION AND HEAT TREATMENT ON PHASE CONSTITUENT AND ORDERING STATE IN CuAlNi ALLOYS

The effect of composition and heat treatment on the phase constituent,the size of B2-andDO_3 derived domains and martensitic thermoelastic behaviour in three CuAlNi alloys havebeen studied by means of metallography,TEM anti X-ray diffraction analyses.It is shownthat the structure of martensite changes from 18R_1 into 2H and the transition temperaturedecreases with the increase of the Al content.Moreover,the size of the B2 and DO_3 deriveddomains decreases with the increase of cooling rate.     

CuAlNi单晶中的DO_3→2H和DO_3→18R转变及其相变热力学SCIEI

在金相显微镜上原位观察了ＣｕＡｌＮｉ单晶在Ｍｓ＜Ｔ＜Ａｆ之间的应力诱发ＤＯ３→２Ｈ和ＤＯ３→１８Ｒ马氏体相变，测定了作为温度函数的相变临界应力和相变熵。采用示差扫描量热计比较了测定的相变熵的可靠性。推出了在３００Ｋ附近ＤＯ３→２Ｈ，ＤＯ３→１８Ｒ和２Ｈ→１８Ｒ马氏体相变的热力学函数。     

热型连铸CuAlNi形状记忆合金丝的性能研究

用热型连铸法制取φ1.5mm的柱晶CuAlNi合金丝,具有轴向排列的柱晶组织.经过900℃固溶处理,拉伸曲线与单晶的相似,具有两个阶段的马氏体转变,抗拉强度可达633MPa,延伸率14.95%.在4%的固定应变下,反复拉伸疲劳断裂次数高达38560次,形状回复率为100%.反复拉伸后在晶界上形成一种新相,有效地松弛了晶界上的应力集中,可能是疲劳寿命大幅度提高的原因.     

Cu-Al-Ni形状记忆合金的发展

对 Cu- Al- Ni形状记忆合金近几年来的研究历史和现状进行了总结和归纳 ,以便人们更好地认识和了解 Cu- Al- Ni合金 ,进而更好地开发利用该合金。本文从 Cu- Al- Ni合金的相图、结构、相变点调整、晶粒细化、双程记忆效应、超弹性等几方面进行了系统的介绍 ,并提出 Cu- Al- Ni形状记忆合金应用推广前必须解决的问题以及其研究方向。     

不同相状态下CuAlNi形状记忆单晶体的超弹性行为

采用沿CuAlNi单晶β相＜011＞方向施加拉应力的方法研究了各特征温度范围的超弹行为。研究表明：由Af以上的在较高应力下冷却至Mf以下卸载时有很高的弹性回复;在Mf以下施加较大载荷并卸载后有超弹应变;Af以上加载贯穿整个降温升温循环过程产生大于8％的应力双程形状记忆效应;Af以上等温负载导致应力诱发马氏体的稳定化,稳定化后的材料可通过热衔环或Af-Md间的加载－立即卸载循环实现“反稳定化”;等温处理还会造成应力诱发马氏体的“再稳定化”。     

热型连铸法制取CuAINi形状记忆合金丝

用热型链铸法从金属液直接成形制取直径１．５ｍｍＣｕＡＩＮｉ合金丝。将铸型温度设定为１１１０℃,可以拉铸出表面光洁、内部含有几个平行晶粒的定向凝固合金丝。拉铸速度５０ｍｍ／ｍｉｎ时,晶粒数较少,晶界平直;拉铸速度８０ｍｍ／ｍｉｎ时,晶粒数较多,晶界较曲折。试样经１０００℃固溶处理后,拉伸强度达５０２Ｎ／ｍｍ＾２,延伸率１４．４％,其中塑性应变８％。在４％固定应变下,反复拉伸的疲劳断裂次数高达７０６次,比文献的列单晶的断裂次数提高４４％。热型连铸法制取铜基形状记忆合金,既可免疫塑性加工的困难,又可获得定向凝固组织,提高合金性能,具有巨大的优越性。     

Deposition and heat treatment of CuAlNi shape memory thin films

CuAlNi thin films were fabricated by magnetron sputtering process. After heat treatment, the thin films presented a shape memory effect. Calowear method was used to measure the thickness of the thin films. SEM, XRD and TEM were used to characterize the thin films. The phase transformation in the thin films was examined by DSC. The deposition rate increased with increasing sputtering power and decreased with increasing Ar pressure. Compared to the composition of the target, both the content of Al and the content of Ni increased a little. The sputtering conditions had little influence on the content of Ni. The content of Al varied slightly with sputtering power, while decreased with increasing Ar pressure. The deposited thin films were columnar. The grain size was very fine. The phases were α‐Cu and α₂. After heat treatment at 800 ^oC/ 60 min + 300 ^oC/ 60 min in vacuum, CuAlNi shape memory thin films were obtained. The phase in the heat‐treated thin films was β₁’ martensite. Martensite transformation was observed and a two‐way shape memory effect could be shown.     

添加元素对铜铝镍记忆合金韧性影响的研究

本文研究了添加元素钇、钛、锆、硼和铬等对 Cu-11.46%Al-2.86%Ni 形状记忆合金的晶粒大小、断口形貌及组织结构的影响.添加上述元素后合金的韧性得以改善,其主要原因是基体内有弥散相析出,从而释放了淬火过程中马氏体形成而产生的淬火应力.在试验范围以内,以添加1%Ti 和1%Y 的增韧效果为最好,添加0.5Cr、1.0%Zr、0.1%B 的效果其次.     

Superelastic behavior and stabilization of stress-induced martensite in Cu-13.4Al-4.0Ni single crystals

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Influence of Liquid Structure on Solid Transformation of CuAlNi Shape Memory Alloy

Molten Cu-13Al and Cu-13Al-4Ni (mass fraction) alloys have been investigated using X-ray diffraction method.A distinct pre-peak has been found in the structure factors. The pre-peak increases its intensity with decreasing temperature and addition of Ni. The structural unit size corresponding to the pre-peak equals to magnitude of (111)planar distance ofβ phase. The appearance of a pre-peak is due to existence of clusters withβ-phase-like structure in melt. Quantity and size of clusters increase with decreasing temperature but their structural unit size remains constant. Cu-13Al-4Ni shape memory alloy ribbons can be fabricated by rapid solidification technique. Order degree of martensite and temperature of the reverse martensitic transformation increase with decreasing liquid quenching temperature. Β phase particles develop from incorporating and growing of the clusters during solidification, thus result in the correlation between liquid structure and solid transformation.