The Characterization Of The Interfacial Microstructun And The Mechanical Properties Of The Diffusion Bonded Metal And Ceramies/Metal Under Multi-Physics Field Coupling

In this paper, the Field activated pressure assisted synthesis (FAPAS) was developed based on the Metal Alloy (MA) and Self-propagating-High-temperature Synthesis (SHS). The composite materials of (TiC-TiB2)/Ni-TiAl-Metal and (AlMgB14-TiB2)-Metal was fabricated by FAPAS. The interfacial structure was the key factor to determine the mechanical properties of the composite materials. In order to invertigate the diffusion process of the dissimilar materials, the Ti and Ni, Mg and Cu were also bonded together by FAPAS. The OM, SEM, TEM, XRD, hardness tester and materials testing machine was used to investigated the diffusion process and the interfacial microstructure. The effect of the testing parameters on the mechanical propertied of the composite materials was also analyzed.(TiC-TiB2)/Ni composite ceramic, the top layer of the composite materials, was prepared in-situ by the combustion synthesis process using Ni, Ti and B4C powders as raw materials. The intermetallic of TiAl was synthesized using Ti and Al as raw materials and at the same time, the composite ceramic of (TiC-TiB2)/Ni was bonded with metal substrate of Ti or Ta. The bonding interface was well and no defects were found at the interface. Fine grained particles are distributed homogeneously in the Ni matrix, with grain size ranging from0.2to1.0μm, which indicates that the full reaction has been completed during the experiments. It had been found that the current and pressure affected the microstructure of the composite ceramics substantially. TiB2and TiC particles comminuted to be broken up and rearranged due to the applied pressure and the current can increase the nucleation rate during the synthesis process. The friction and wear properties of the (TiC-TiB2)/Ni ceramic were evaluated by sliding against a GCr15disk at temperatures from ambient up to400℃. The experimental results showed that the friction coefficient of the (TiC-TiB2)/Ni ceramic decreased with increasing testing temperature, load, and sliding speed. However, the loss rate decreased at higher temperature and increased at higher load and higher sliding speed. The oxide films of Fe2O3, TiO2, and B2O3formed during the friction process played an important role in lubrication, which results in a smaller friction coefficient. The wear resistance of composites containing80%(TiC-TiB2) compared to70%(TiC-TiB2) shows a mild enhancement due to the high strength and high hardness of TiC and TiB2.Using powders of B, Mg, Al and TiB2as raw materials, the ultra hard material AlMgB14-TiB2was fabricated and bonded with Mo and Nb metal substrate at one step. It was indicated that the B diffused into the metal substrate more easily. There was a gradual increase in hardness from the metal substrate to AlMgB14-TiB2. The hardness increased from about2000HV1.0at the bonding interface to about3801HV1.0at AlMgB14-TiB2.Three intermetallic compounds were formed at the interface of Ti-Ni diffusion couples, i.e. Ti2Ni、 TiNi and TiNi3. The thickness of the three compounds increased as the diffusion temperature increased. Testing results showed a parabolic growth for all the three phases with the increase of the diffusion time. Compared with Ti2Ni and TiNi3, the TiNi compound was more easily affected by the diffusion temperature. The shear experiments showed that the fractures were mostly brittle, i.e. inter-crystalline. The fracture occurred at TiNi3when the Ti2Ni was thin, but it occurred at Ti2Ni when some TiNi3was consumed by Ti atom to form TiNi. The order of the mechanical properties of the three intermetallic compounds can be list as follows:TiNi>Ti2Ni>TiNi3. Two intermetallic compounds were formed at the interface of magnesium alloy-Cu diffusion couples, i.e. Cu2Mg and Mg2Cu. Just as the Ti-Ni experimental results, magnesium alloy-Cu interfacial testing results also show a parabolic growth for all two phases with the increase of the diffusion time. The diffusion rate of the Al was affected by the temperature substantially. Almost no MgAlCu formed at the interface at450℃, but it would formed at475℃, and the thickness of the MgAlCu compound would increase as the diffusion time increased. Eutectic layers was formed at500℃, and the distribution of the eutectic layer increased as the diffusion time increased.Compared with the traditional diffusion bonding, electric current can decrease the diffusion energy and promote the reaction dramatically. The diffusion energy of Ti2Ni, TiNi and TiNi3reduced by60%,48%and45%respectively. As for magnesium alloy-Cu couples, compared the diffusion energy of700A and750A respectively, the diffusion energy reduced by36.1%.Based on the experimental result, the interfacial diffusion phase diagram was depicted. The interfacial diffusion phase diagram is quite different form the equilibrium phase diagram. It was formulated to show the formation order of the phases of the diffusion couples. And it’s of great importance to explore the mechanism of the diffusion process.