Study On The Microstructures And Properties Of Ti-Fe-based Alloys Containing Carbon

In the Ti-Fe alloys, the composite Ti65Fe35 alloy exhibits a high mechanical strength of 2.2GPa at 6.7% ductility. The Ti-Fe alloys have a nonequilibrium phase composition which consists of ordered Ti Fe and disordered β-Ti. The formation of a supersaturated β-Ti solid solution and a disperse hard Ti Fe intermetallic compound with rounded morphology distributed in the β-Ti matrix results in the high strength and enhanced ductility in Ti65Fe35 alloy. The strength and plasticity of the alloy can be improved by adding third or fourth elements to Ti-Fe. In this paper, the mechanical properties and microstructure of Ti-Fe-(Al) alloys were studied.We improved the mechanical properties and microstructure of the alloys by the addition of carbon element.The vacuum arc melting furnace was used in the process of the experiment. The structure of the ingot was examined by X-ray diffractometry(XRD), scanning electron microscopy(SEM) equipped with an energy dispersive X-ray spectrometer(EDX) and transmission electron microscope(TEM). The mechanical properties of the alloys were tested by INSTRON-5982 universal mechanical testing machine and hardness tester. The fracture morphology was analyzed by scanning electron microscope.Research results show that for the Ti-Fe binary alloys, with the increase of Fe content the hardness of the alloys increases. Hypereutectic, eutectic and hypoeutectic alloys were consisted of ordered 3? structure of Ti Fe phase and disordered 3?, structure of β-Ti phase. When Fe content varies in the range of 10%- 20%, all of the alloys are consisted of β-Ti solid solution composition, the yield strength decreases while the ductility increases when the Fe content reduces. In the compression test, the Ti90Fe10 alloy has not been broken until the flattening.A small amount of carbon(less than 1at. %) was added into the alloys. The Vicker’s hardness of all the alloys was improved about 10~50. The mechanical property of some alloys was remarkably improved. Ti65(Fe97.45C2.55)35 alloy exhibited high strength of 2761 MPa and, large plastic strain of 10.7%, which is larger than the ductility value of 0.7% obtained in the Ti65Fe35 alloy. The phase morphology of the Ti65Fe35 alloy was changed with the addition of carbon, the dendrite morphology tends to become spherulitic morphology in the microstructure of the alloy. Between Ti Fe dendrites, alloy carbide particles are formed. According to the structure of the alloy carbide particles, the chemical composition of those particles is Ti C. In the solidification, Ti C ceramic precipitated first, which provides nucleation center for the Ti Fe phase. Compared compression curve of Ti80Fe20 with Ti80(Fe97.45C2.55) 20, the yield strength increases from 1684 MPa to 1755 MPa, ductility improves from 2.1% to 24.5% evidently. On the basis of this, we have added a trace C element to Ti-6Al-4Fe, the nominal composition is Ti-6Al-4Fe-0.02 C, and we have studied the Ti-3Al-10 Fe and Ti-3Al-10Fe-0.06 C, the four kind of alloys are hot rolling in 900 degrees and water quenching, the four kind of alloys have good tensile properties.