As the lightest structural materials, Mg alloys show great effectiveness at energy saving and emission reduction when applied in the automotive and aerospace fields. In particular, Zr-bearing Mg alloys (non-Al containing) exhibit high strengths and elevated-temperature usage values. Zr is the most powerful grain refiner, and it provides fine grain sizes, uniformities in microstructural and mechanical properties and processing formability for Mg alloys. Due to the importance of Zr alloying, this review paper systematically summarizes the latest research progress in the grain refinement effects of Zr on Mg alloys. The main points are reviewed, including the alloying process of Zr, the grain refinement mechanism of Zr, factors affecting the grain refinement effects of Zr, and methods improving grain refinement efficiency of Zr. This paper provides a comprehensive understating of grain refinement effects of Zr on Mg alloys for the researchers and engineers.

Restenosis after stent implantation is a major limitation of revascularization technique. Retrieving the stent safely and smoothly after the vascular remodeling is completed shows important clinical significance. In this paper, a novel retrievable peripheral vascular stent and its modified retrieval platform were developed and the finite element analysis (FEA) model was established to study the retrieval process of the stent. Meanwhile, the safety and feasibility of the retrievable stent were assessed through in vivo experiments. The maximum strain of the stent is 6.87% during the whole retrieval process, which is less than the ultimate elastic strain of nitinol alloy. The simulation results indicate that the stent is not damaged or stuck during the whole retrieval process. Finally, the stents were implanted into Bama miniature pigs to assess the retrieval process, and the results suggest that the stents can be retrieved successfully within a short period of time after implantation, and minor local mechanical injury can be found in the intimal layer of the blood vessel due to the expansion and contraction of the stent. Studies presented in this work illustrate the feasibility of a novel retrievable peripheral vascular stent, providing an additional avenue to avoid in-stent restenosis.