Fabrication, Microstructure And Mechanical Properties Of SiC Particle-reinforced Titanium Aluminide Laminate Composites

As a novel material, the titanium aluminide intermetallic-laminate composite has an application prospect in aerospace, warships, weapons and other fields owing to its low density,high specific strength, high melting point, high elastic modulus, excellent oxidation resistance and corrosion resistance. However, in this laminated composite Ti/Al3Ti, the Ti as toughening phase improves the plastic properties of Al3Ti through the layer structure between Ti and Al3Ti, which does not improve the strength of Al3Ti. In order to enhance the strength of metal-intermetallic-laminate composite Ti/Al3Ti, SiC particle, with low density, low expansion,high-thermal conductivity,high elastic modulus,high hardness, high stiffness and isotropy, was chosen to reinforce the laminate composite. SiC particle-reinforced laminate composite was synthesized successfully using SiC particle, Al particle and Ti foils by ball milling, powder metallurgy, hot rolling and vacuum hot-pressing sintering techniques. The strength and plasticity of SiCp-Ti/Al3Ti laminate composite are superior to that of Ti/Al3Ti laminate composite by introducing SiC particles into Al3Ti matrix to form SiC layer.The process parameters of SiC particle-reinforced laminate composite were optimized through adding SiC particles in different approaches. In SiCp-Ti/Al3Ti laminate composite, the microstructure and interface bonding characteristics of SiC-Al and Al-Al3Ti were observed by scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS); the compositions of this laminate composite were characterized by X-ray diffractometer (XRD).The experimental results indicate that the newly formed intermediate layer in Al3Ti layer consists of residual A1 and SiC particles. The interface between SiC particle and residual Al bonds well without voids or defects. There is a diffusion layer with a certain thickness～3μm in the interface between SiC particle and residual Al detected by EDS line scanning technique.The XRD analysis results show that there are five phases in this composite, i.e. Ti, Al3Ti, SiC,Al and a very small amount of Al2O3.The physical property indexes of the composite, i.e. density, hardness and modulus, were determined using Archimedes principle, Vickers microhardness and Elastic modulus measurement in this work. And the mechanical properties of SiC particle-reinforced laminate composite were tested by Instron 5500R load frame and Split Hopkinson Pressure Bar. The experimental results demonstrated that the mechanical properties of SiC particle-reinforced laminate composite were superior to that of Ti/Al3Ti laminate composite. The compressive strength of SiCp-Ti/Al3Ti laminate composite increased and the fracture strain decreased with decreasing volume fraction of residual Al. The compressive strength increased but the fracture strain decreased with increasing strain rate. The tensile strength and fracture strain of SiCp-Ti/Al3Ti laminate composites are 446MPa and 4.3%, respectively. According to the fracture morphology, it can be indicated that in SiCp-Ti/Al3Ti laminate composite, there are different fracture modes in different layers, which is not dependent on the stress state(compressive state or tensile state). That is to say, Ti layer with dimples belongs to ductile fracture; while the fracture mode of Al3Ti layer is mixed with intergranular and transgranular fracture because of nature brittlness of Al3Ti. In the layer with SiC particle and residual Al,fracture modes mainly included the ductile fracture in residual Al, interface fracture between particles and residual Al, and brittle fracture of SiC particles.