**Reza Hashemi**

College of Science and Engineering, Medical Device Research Institute, Flinders University, Tonsley SA 5042, Australia; reza.hashemi@flinders.edu.au; Tel.: +61-8-82012782

Received: 30 April 2020; Accepted: 15 May 2020; Published: 19 May 2020

#### **1. Introduction and Scope**

Metallic biomaterials (biometals) are widely used for the manufacture of medical implants, ranging from load-bearing orthopaedic prostheses to dental and cardiovascular implants, because of their favourable combination of properties including high strength, fracture toughness, biocompatibility, and wear and corrosion resistance. Additionally, they can be fabricated using well-established techniques (such as casting and forging), and recently, additive manufacturing to produce complex and customised implants. Examples of metals and metal alloys that are used for the fabrication of implants include the following: Ti-based alloys (e.g., Ti6Al4V and Ti6Al7Nb), Co-based alloys (e.g., CoCrMo and CoNi), austenitic stainless steels (e.g., SS316L), Zr-Nb alloys, Ni-Ti Alloys, Mg alloys, porous tantalum foams, and precious metals and alloys.

Owing to the significant consequences of implant material failure/degradation, in terms of both personal and financial burden, failure analysis of biometals (in-vivo, in-vitro, and retrieval) has always been of paramount importance in order to understand the failure mechanisms and implement suitable solutions with the aim to improve the longevity of implants in the body. This Special Issue presents some of the latest developments and findings in the area of biometals failure including fatigue, fracture, corrosion, and fretting wear on a range of conventional biometals as well as porous materials and new generation titanium alloys.
