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Metals
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Shape Memory Alloys 2022
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Shape Memory Alloys 2022

A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Entropic Alloys and Meta-Metals".

Deadline for manuscript submissions: closed (31 July 2022) | Viewed by 6812

Special Issue Editor

Prof. Dr. Shijie Hao

E-Mail Website
Guest Editor
College of New Energy and Materials, China University of Petroleum, Beijing, China
Interests: titanium nickelide; shape memory alloy; martensitic transformations; nanocrystalline alloys; additive manufacturing; high-energy X-ray diffraction

Special Issue Information

Dear Colleagues,

Shape memory alloys are endowed with a unique shape memory effect and pseudoelasticity via their essential thermoelastic martensitic transformation. Near-equiatomic NiTi alloys in particular, with their excellent mechanical properties, good biocompatibility, and high corrosion resistance, have been most widely used in the aerospace and automobile industries, in consumer goods, and in medical technology, as fasteners, actuators, stents, and medical guidewires, to name a few. A great deal of research efforts has been devoted to shape memory alloys. At present, the exploitation of shape memory alloys with ultra-high performance is a major research trend, including wide temperature range pseudoelasticity, high shape recovery rate, cycling durability, and excellent elastocaloric and damping properties. On the other hand, limited by the common poor machinability and weldability of shape memory alloys, conventional bulk shape memory alloys (wire, sheet) cannot meet the demands of complex-shaped structural parts in special service environments. Recently, the potential ability of additive manufactured (or 3D printing) shape memory alloys to achieve the formation of various structural parts has been extensively studied. However, due to the uniqueness of the additive manufacturing process, many new scientific issues have emerged that need to be investigated on shape memory alloys compared to traditional metallurgy.

In this Special Issue, we welcome reviews and articles in the areas of preparation technology, novel functional performance, principle and micromechanisms, and special spatial structures and applications of shape memory alloys.

Prof. Dr. Shijie Hao
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Metals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Shape memory alloys
  • Structure
  • Martensitic transformation
  • Pseudoelasticity
  • Shape memory
  • Elastocaloric effect
  • Additive manufacturing

Published Papers (3 papers)

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Research

8 pages, 1722 KiB  
Article
Study on the Microstructure and Mechanical Properties of 60NiTi Alloy Quenched by Hot Oil
by Jie Zhou, Cheng Wang, Yichen Fu, Chenxi Dong, Hongchao Zhang, Yunpeng Hu and Shijie Hao
Metals 2022, 12(9), 1513; https://doi.org/10.3390/met12091513 - 13 Sep 2022
Cited by 2 | Viewed by 1204
Abstract
60NiTi alloys have a tremendous potential to be used in aerospace, marine and automotive industries. There is still a need to further improve the deformability due to the high brittleness of the previously prepared 60NiTi. In this work, 200 °C hot silicone oil [...] Read more.
60NiTi alloys have a tremendous potential to be used in aerospace, marine and automotive industries. There is still a need to further improve the deformability due to the high brittleness of the previously prepared 60NiTi. In this work, 200 °C hot silicone oil was selected as the quenching medium for 60NiTi for the first time to overcome its high brittleness. It is found that the unique microstructure of 60NiTi quenched by hot oil has a lamellar structure composed of a channel-like NiTi matrix and lenticular Ni4Ti3 phase containing a nano-lath NiTi phase. The 60NiTi exhibits a high compression fracture strain of 10% and large reversible strain of 7.5%; which originates from the superelastic behavior of the NiTi SMA constituent. Upon loading, the R phase reorientation releases the stress concentration at the initial stage; while the stress-induced martensitic transformation accommodates the large elastic deformation of the Ni4Ti3 phase at the later stage. This synergistic effect of the two promotes the compressive deformability. Full article
(This article belongs to the Special Issue Shape Memory Alloys 2022)
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12 pages, 6293 KiB  
Article
Selective Laser Melting of 60NiTi Alloy with Superior Wear Resistance
by Fangmin Guo, Hui Shen, Zhiwei Xiong, Ying Yang, Xin Tong, Yanbao Guo and Shijie Hao
Metals 2022, 12(4), 620; https://doi.org/10.3390/met12040620 - 3 Apr 2022
Cited by 8 | Viewed by 2222
Abstract
In this work, the selective laser melting (SLM) 60NiTi alloy was successfully fabricated. Through designing an orthogonal experiment of parameters optimization including laser power (P) and scanning speed (v), the optimal parameters window with both high forming quality and appropriate composition proportion was [...] Read more.
In this work, the selective laser melting (SLM) 60NiTi alloy was successfully fabricated. Through designing an orthogonal experiment of parameters optimization including laser power (P) and scanning speed (v), the optimal parameters window with both high forming quality and appropriate composition proportion was established. The SLM 60NiTi can exhibit high relative density (>98%) and low Ni loss (<0.2 at.%) at the parameter window of P = 80–90 W, v = 300–350 mm/s, and energy density of 145–155 J/mm3. The optimally-selected SLM 60NiTi exhibits a high compression strength of 2.2 GPa and large reversible strain of 7% due to the reversible stress-induced martensitic transformation of the NiTi phase and the large elastic strain of the Ni4Ti3 phase. It also exhibits superior wear resistance to conventional casting solution treated 60NiTi because the NiTi phase formed in an SLM repeated thermal cycle possesses a lower solution Ni atom and thus lower critical stress for martensitic transformation, and is more prone to undergo martensitic transformation upon friction and wear. Full article
(This article belongs to the Special Issue Shape Memory Alloys 2022)
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11 pages, 3614 KiB  
Article
The Effect of Wall Thickness and Scanning Speed on the Martensitic Transformation and Tensile Properties of Selective Laser Melted NiTi Thin-Wall Structures
by Fangmin Guo, Yanbao Guo, Xiangguang Kong, Zhiwei Xiong and Shijie Hao
Metals 2022, 12(3), 519; https://doi.org/10.3390/met12030519 - 18 Mar 2022
Cited by 4 | Viewed by 2064
Abstract
In this study, we analyzed the coupling effect of laser scanning speed and wall thickness on the phase transformation behavior and tensile properties of selective laser melted NiTi thin-wall structures. It is demonstrated that either scanning speed or wall thickness has their respective [...] Read more.
In this study, we analyzed the coupling effect of laser scanning speed and wall thickness on the phase transformation behavior and tensile properties of selective laser melted NiTi thin-wall structures. It is demonstrated that either scanning speed or wall thickness has their respective influence rule, whereas this influence could be changed when coupling them together; that is, under different scanning speeds, the effect of wall thickness could be different. It is found that the deviation of phase transformation temperature among different wall thicknesses is ~3.7 °C at 400 mm/s, while this deviation increases to ~23.5 °C at 600 mm/s. However, the deviation of phase transformation peak width among different wall thicknesses shows little change under different scanning speeds. At low scanning speed, the samples with thicker wall thickness exhibit better tensile ductility than thinner, whereas they all show poor tensile properties and brittle behavior at high scanning speed. This uncertain influence rule is mainly due to the interaction effect between different thermal histories generated by wall thickness and scanning speed. Full article
(This article belongs to the Special Issue Shape Memory Alloys 2022)
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