Microstructural Characterization and Mechanical Behavior of NiTi Shape Memory Alloys Ultrasonic Joints Using Cu Interlayer.
Microstructural Characterization and Mechanical Behavior of NiTi Shape Memory Alloys Ultrasonic Joints Using Cu Interlayer.
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使用 Cu 夹层的 NiTi 形状记忆合金超声接头的微观结构表征和机械行为
DOI：
10.3390/ma11101830
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发表时间：
2018-09-26
期刊：
影响因子：
--
通讯作者：
Luo Z
中科院分区：
文献类型：
--
作者：
Zhang W;Ao S;Oliveira JP;Zeng Z;Huang Y;Luo Z
NiTi形状记忆合金（SMA）是一类功能材料，可以显着变形并通过可逆马氏体相变恢复其原始形状。开发有效的连接技术可以扩大 SMA 在医学和工程领域的应用。在这项研究中，超声波点焊 (USW)（一种固态连接技术）被用于在两个连接板之间使用铜夹层来连接镍钛板。研究了USW工艺对NiTi接头微观结构特征和力学行为的影响。与传统的熔焊技术相比，接头中不会形成金属间化合物，这对于此类特殊合金来说极其重要。连接机制涉及剪切塑性变形、机械联锁和微焊缝形成的组合。通过较高的焊接能量水平可以获得更好的结合界面，这有助于更高的拉伸载荷。发生界面断裂模式，断裂表面呈现脆性和韧性特征，存在撕裂脊和韧窝。断裂在接头边界的薄弱区域开始，然后通过该区域扩展，导致断裂界面处的铜箔撕裂。
NiTi shape memory alloys (SMAs) are a class of functional materials which can be significantly deformed and recover their original shape via a reversible martensitic phase transformation. Developing effective joining techniques can expand the application of SMAs in the medical and engineering fields. In this study, ultrasonic spot welding (USW), a solid-state joining technique, was used to join NiTi sheets using a Cu interlayer in between the two joining sheets. The influence of USW process on the microstructural characteristics and mechanical behavior of the NiTi joints was investigated. Compared with conventional fusion welding techniques, no intermetallic compounds formed in the joints, which is extreme importance for this particular class of alloys. The joining mechanisms involve a combination of shear plastic deformation, mechanical interlocking and formation of micro-welds. A better bonding interface was obtained with higher welding energy levels, which contributed to a higher tensile load. An interfacial fracture mode occurred and the fracture surfaces exhibited both brittle and ductile-like characteristics with the existence of tear ridges and dimples. The fracture initiated at the weak region of the joint border and then propagated through it, leading to tearing of Cu foil at the fracture interface.
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