Metallurgical Considerations for Machining Magnesium Alloys

Process mechanics and surface integrity by high-speed dry milling of biodegradable magnesium–calcium implant alloys

“…Feed has the most significant influence on surface roughness, while speed and depth-of-cut had no apparent trends on R a . Compared to the reported negative influence of FBU on roughness [5,6], it is very interesting to note that R a even slightly decreases when tool/ material adhesion accumulates with cutting speed in Fig. 5a-c.…”

“…However, machining of functional elements such as holes and threads of orthopedic implants is often required. The bulk research on machining Mg alloys including AZ91 is limited to automotive applications [5][6][7][8][9]. Machining of Mg alloys is characterized by low power requirements, long tool life, high achievable surface quality, and short-breaking chips [10].…”

“…On the other hand, dry machining produces high temperature which promotes adhesion between cutting tool/work material as well as flank build-up (FBU), in particular when a critical cutting speed is exceeded. FBU is initiated by a certain affinity between cutting tool/work materials, sufficient cutting temperature, and the existence of hard particles embedded in the soft matrix [5][6][7]. FBU leads to vibrations, low surface finish, poor dimension accuracy, or even risk of chip ignition, which are major barriers for high-speed dry machining Mg alloys [5][6][7][8][9]11].…”

Surface integrity of biodegradable orthopedic magnesium–calcium alloy by high-speed dry face milling

“…For high speed dry face milling of MgCa0.8 with PCD inserts, FBU formation mechanism theorized in Ref. [9] needs to include another step occurring after FBU formation, and that is FBU detachment from the tool. The developed FBU results in severe interactions around cutting edge zone and as a result, high amounts of heat will be generated.…”

“…HSM of Mg alloys is defined as machining with cutting speeds between 600 and 5,000 m/ min based on being a finish cut or a rough cut [9,10]. The majority of work in machining of Mg and its alloys has been conducted for automotive industry through the period of last two decades.…”