Properties of Cu-Based Shape-Memory Alloys Prepared by Selective Laser Melting
Properties of Cu-Based Shape-Memory Alloys Prepared by Selective Laser Melting
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DOI：
10.1007/s40830-016-0088-6
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发表时间：
2017-03-01
影响因子：
2.2
通讯作者：
Pauly, S.
中科院分区：
文献类型：
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作者：
Gustmann, T.;dos Santos, J. M.;Pauly, S.
采用选择性激光熔凝(SLM)技术制备了名义成分(wt.%)为Cu11.85Al-3.2Ni-3Mn和Cu11.35Al-3.2Ni-3Mn0.5Zr的两种形状记忆合金。对参数进行了优化以确定工艺窗口，在该窗口中可以获得几乎完全致密的样品。对其显微组织进行了分析，并与其形状记忆行为和力学性能进行了关联。还制作了吸力铸型试件以供比较。所有样品主要形成β(1)‘马氏体，但0.5wt.%的Zr稳定了Y相(Cu2AlZr)，其形态取决于热历史和冷却速度。退火后，Y相主要存在于阻碍晶界粗化的晶界。由于这里采用了较高的冷却速度，在所制备的样品中，Zr主要溶解在马氏体中，只有在达到临界冷却速度时，它才具有细化晶粒的作用。含Zr样品的相变温度升高，而Y相似乎是马氏体向奥氏体跃变的原因。所有的样品都是相对韧性的，因为它们大多以穿晶方式断裂，表现出典型的双屈服。选择性激光熔化允许调整加工过程中已经存在的相变温度和机械性能，而不需要随后的热处理。
Two shape-memory alloys with the nominal compositions (in wt.%) Cu-11.85Al-3.2Ni-3Mn and Cu-11.35Al-3.2Ni-3Mn-0.5Zr were prepared by selective laser melting (SLM). The parameters were optimised to identify the process window, in which almost fully dense samples can be obtained. Their microstructures were analysed and correlated with the shape-memory behaviour as well as the mechanical properties. Suction-cast specimens were also produced for comparison. Mainly, beta(1)' martensite forms in all samples, but 0.5 wt.% of Zr stabilises the Y phase (Cu2AlZr), and its morphology depends on the thermal history and cooling rate. After annealing, the Y phase is primarily found at the grain boundaries hampering grain coarsening. Due to the relative high cooling rates applied here, Zr is mostly dissolved in the martensite in the as-prepared samples and it has a grain-refining effect only up to a critical cooling rate. The Zr-containing samples have increased transformation temperatures, and the Y phase seems to be responsible for the jerky martensite-to-austenite transformation. All the samples are relatively ductile because they mostly fracture in a transgranular manner, exhibiting the typical double yielding. Selective laser melting allows the adjustment of the transformation temperatures and the mechanical properties already during processing without the need of a subsequent heat treatment.