Improvement of mechanical properties of Fe-based alloys by application of rapid solidification method and Ti doping

Nowadays, the industry is looking for the modern functional materials with unique functional properties [1, 2]. Very interesting group of alloys for special applications are those made on the basis of iron modified with titanium. These alloys, due to their increased strength and relatively low density (ρTi = 4.507 g/cm3), can be used in many industries. Ti admixture in this type of alloys results in a partial or complete oxidation of the surface, as the Ti has high affinity for oxygen [3]. Titanium is known to be an element well tolerated by the human body, and therefore it is successfully used in implantology [3, 4]. It is applied to produce cores, both for large hip implants, as well for mini dental implants. However, without proper chemical or mechanical treatment, titanium does not overgrown tissue and is only a foreign body. Recently, blasting method has been a very popular technique for refinement of the top layer of alloys containing titanium, regarding dental implants. The technique is very simple and cheap, but it is not without drawbacks as stratification because of grit used in mechanical polishing. Its small parts are sticking into the surface of the implant. What in turn leads to tearing down the structure of the surface. So, it can be stated that a lot depends on the grit used in the discussed process, which usually are small aluminum granules. The problem of aluminum contamination of dental implants has been eliminated by the chemical digestion process. Materials containing titanium are characterized by low weight and relatively high strength, they are used to build most of metal components used in the aerospace and military industry [5, 6]. Titanium alloys are also adopted in jewelry and become a good alternative to a few percent of the population showing an allergic reaction to silver, gold or platinum. They were also widely used in optics as part of eyeglass frames (flex-titanium, β-titanium). The mentioned above examples of application of the titanium alloys, refer to alloys produced in a conventional manner, that is with a standard cooling rate (air, or with the kokila). As indicated in the papers [7, 8], the solidification speed in this type of alloys determines their structural construction, and more particularly has an effect on the microstructure. The increasing cooling rate can lead to an amorphous structure, which is characterized by topological and chemical disorder in the arrangement of atoms. The amorphous bodies, with the addition of Ti, can be obtained when the cooling speed is in the range of 10 to 10 K/s, with a thickness ranging from several mm to a dozen m [9÷12]. At the highest cooling speeds it possible to obtain bulk materials, based on iron with the addition of titanium, in the form of thin, very durable, hard and plastic tapes. Amorphous state itself, due to the presence of atoms in a volume arrangement, has a high affinity to the structure found in the human body. Biocompatibility study, carried out in Ringer's medium for amorphous alloys, shows extremely high tolerance [4]. Such a form of the materials may be used further for medical applications such as the construction of membranes or indestructible diaphragms. This paper presents the microstructure and mechanical properties studies of selected Fe73T5Y3B19, Fe61Co10Y8Ti1B20 alloys obtained at the clotting speeds of 10÷10 K/s, in the form of thin ribbons of about 30 m in thickness.