كليدواژه :
Mechanical alloying , Fe , Mn alloys , Biodegradable , Microstructure
چكيده فارسي :
During the past decades, mechanical milling has attracted considerable attention as an effective solution to grind powders into fine particles in order to produce a homogenous structure for composites. Ball milling in a concealed container creates localized high pressure. Also, it generates mechanical activation by increasing the material reactivity and uniformity of the spatial distribution of elements. However, the processing parameters which impact the structure and performance of the synthesized materials must be carefully chosen while ball milling. The factors that determine the quality of dispersion include the milling time (MT), ball-to-powder mass ratio (BPMR), grinding medium (GM), milling speed (MS), and milling atmosphere (MAT). Biodegradable metals made from iron, magnesium, zinc, and their alloys have viewed as the promising new materials for making temporary medical implants. Fe-Mn alloys are used as biodegradable materials (BDMs). These materials are used for medical applications. Fe–Mn-based alloys have been designed as BDMs for medical applications, including fracture fixation and temporary orthopedic devices, cardiovascular support, and stent implantation. The aim of this work is to develop new biodegradable alloys based on the zinc addition to Fe-Mn alloy. In this study, a set of Fe-30Mn-5Zn alloys were synthesized by means of mechanical alloying and assessed for their microstructure. Powders of iron and manganese with a purity of 99.9% and zinc (99.9%) were used to prepare two set alloys: Fe-30Mn and Fe-30Mn-5Zn (all in wt%). The powder mixtures were mechanically alloyed using planetary ball milling machine at a rotation speed of 300 rpm, 20 h, and 10:1 ball-to-powder weight ratio. A 0.5 wt% toluene (99.9%) was added into the mixture as a process control agent to avoid cold welding. The process was performed continuously to complete the milling time (MT) by repeating a milling cycle comprising four stages: rotation in the forward path for 60 min; a stop for 15 min; rotation in the reverse path for 60 min; and one more stop for 15 min. Stops in each cycle were implemented to inhibit overheating inside the milling containers. The mechanical milling powders phase composition was examined by an X-ray diffraction (XRD). The XRD pattern detected Fe, Mn, and Zn Peaks as a mixed powder mixture. The results from XRD patterns indicate a peak broadening at longer milling time which can be attributed to the reduction of the crystallite size and the accumulation of strain. The microstructure of the alloys was examined by scanning electron microscopy (SEM). SEM results confirm that Zinc particles were distributed homogeneously in the microstructure.
