Effect of Homogenization on the Transformation Temperatures and Mechanical Properties of Cu15Ni35Hf12.5Ti25Zr12.5 and Cu15Ni35Hf15Ti20Zr15 High-Entropy Shape Memory Alloys.

The major challenge of high-temperature shape memory alloys (SMAs) is the collocation of phase transition temperatures (TTs: Ms, Mf, As, Af) with the mechanical properties required for application. Previous research has shown that the addition of Hf and Zr into NiTi shape memory alloys (SMAs) increases TTs. Modulating the ratio of Hf and Zr can control the phase transformation temperature, and applying thermal treatments can also achieve the same goal. However, the influence of thermal treatments and precipitates on mechanical properties has not been widely discussed in previous studies. In this study, we prepared two different kinds of shape memory alloys and analyzed their phase transformation temperatures after homogenization. Homogenization successfully eliminated dendrites and inter-dendrites in the as-cast states, resulting in a reduction in the phase transformation temperatures. XRD patterns indicated the presence of B2 peaks in the as-homogenized states, demonstrating a decrease in phase transformation temperatures. Mechanical properties, such as elongation and hardness, were improved due to the uniform microstructures achieved after homogenization. Moreover, we discovered that different additions of Hf and Zr resulted in distinct properties. Alloys with lower Hf and Zr had lower phase transformation temperatures, followed by higher fracture stress and elongation.

Effect of Mo on the Mechanical and Corrosion Behaviors in Non-Equal Molar AlCrFeMnNi BCC High-Entropy Alloys.

Co-free body-centered cubic (bcc) high-entropy alloys (HEAs) are prepared, and the elevated mechanical property and corrosion property of the Al0.4CrFe1.5MnNi0.5Mox (x = 0 and 0.1) alloys are studied. The Vickers hardness (HV) of the as-homogenized state is between HV 350 and HV 400. Both alloys are provided with nano-scale NiAl-rich B2 precipitates which contribute to the strength at high-temperature. In addition, adding Mo in the present alloy strengthens by σ phase. Al0.4CrFe1.5MnNi0.5Mo0.1 exhibited outstanding tensile properties, with a yield strength of 413 MPa and ultimate tensile strength of 430 MPa in the elevated tensile test at 600 °C, which is better than that of Al0.4CrFe1.5MnNi0.5 alloy. Through potentiodynamic polarization testing in 0.5 M H2SO4 solution and electrochemical impedance spectroscopy (EIS), it is shown that adding Mo can effectively reduce the corrosion current density and improve the impedance of passive film, since the passivation layer is formed and stable.

Acupuncture-induced popliteal arteriovenous fistula successfully treated with percutaneous endovascular intervention.

A 39-year-old female visited our cardiovascular outpatient department with paresthesia and soreness around the right popliteal fossa, where thrill was palpable. There was no history of trauma, apart from her having undergone acupuncture several years previously. An arteriovenous fistula (AVF) was diagnosed by vascular ultrasonography and magnetic resonance imaging. Angiography confirmed the presence of an AVF fed by the medial geniculate artery. Transarterial embolization was performed to close the AVF using coils and tissue adhesive. To the best of our knowledge, acupuncture-induced AVF has not been previously reported. We present a case demonstrating the merits of percutaneous endovascular intervention for treating this rare complication. The additional administration of a tissue adhesive can achieve complete closure of the AVF in the event of an unsatisfactory result following coil embolization. Doctors should be aware of the potential vascular complications of acupuncture, and of the management options.