The Synthesis Of B₄c Composite And The Research Of Its Corrosion Behavior In Sea Water

The development of marine science and technology, which is the integration of many subjects, is a systematic project. However, as to the basis, it relies on materials technology and its breakthroughs, in particular, depends on the specific materials used in marine research. Materials used in the ocean are under the water stress and the erosion of marine microorganisms. In the special marine environment, marine materials must have the special qualities, such as high strength, corrosion resistance, anti-adhesion, light weight, high toughness and so on.Boron carbide ceramics, which has the excellent quality such as low density, high hardness, high strength, wear resistance, corrosion resistance, are the ideal materials for ocean; TiAl alloy has low density, as sintering aids, it can improve the sintering of boron carbide ceramics and the in situ second phase particles can be generated during sintering to improve the mechanical properties of boron carbide ceramics. In this paper, B4C ceramics were sintered using TiAl alloy as their sintering aids, and the preparation processes, mechanical properties, micostructure, phase composition, sintering mechanism, toughening mechanism and corrosion resistance of the composits were studied.TiAl alloy powder was prepared by mechanical alloying. The main components of this powder are solid solution and TiAl intermetallic compound. The B4C ceramics were sintered using this powder as sintering additives. The main phases composition of the composits are titanium diboride (TiB2), boron-rich phase (B12 (BC2) 0.85 (B3) 0.85), graphite (C) and aluminum diboride (Al6.3B88). When the content of TiAl alloy powder is 20wt%, the composite material has the best mechanical properties, the bending strength is 437.29 MPa, the fracture toughness is 5.72 MPa·m1/2. The reason why the best mechanical properties were possessed lies in the in situ rod-like crystal and nano-TiB2 particles generated during sintering, which played an important role in toughening. The properties of seawater corrosion resistance of 10wt% TiAlB4C,20wt% TiAl/B4C,30wt% TiAl/B4C and 40wt% TiAl/B4C were studied. The mass of the samples have no change whitin the error tolarence after 60 days immersion in the seawater. The resistance to seawater corrosion from strong to weak was 10wt% TiAl/B4C,30wt% TiAl/B4C,40wt% TiAl/B4C,20wt% TiAl/B4C. In the experimental period, the corrosion resistance of the samples has changed, but with the different rules. The corrosion resistanc of 10wt% TiAl/B4C and 20wt% TiAl/B4C declined first and then increased; 30wt% TiAl/B4C declined first and then increased and again declined; 40wt% TiAl/B4C increased first and then declined. The corrosion prosesses of the composits can be divided into three phases:harmful particles in seawater penetrate the surface protective film of the material; the TiB2 phase was corrosed by seawater and the TiO2 protective film regenerated on the TiB2 phase. Through the cycles of these three processes, the corrosion resistance of the samples changed, and the different content of each phase in the material led to the different occurring time of each process. The graphite is the cathode and the TiB2 is the anode during the corrosion process, they formed primary cell, and the electrod reactions are:Anode reaction:TiB2+8H2O=TiO2+2H3BO3+10H++10eCathode reaction:O2+4H2O+4e=4OH-Overall reaction:2TiB2+5O2+2H2O=2TiO2+4H3BO3 The corrosion processes of composite materials are right the electrochemical reaction processes.TiAl/B4C composite materials were designed and prepared in this experiment. The process of design and sythesis of the composite was studied; the sintering mechanisms, toughening mechanisms and the ability of seawater corrosion resistance were explored and the composite with low density, high strength, and excellent seawater corrosion resistance was possessed.