HOT-PRESSING OF PLASMA-SPRAYED SIC FIBER-REINFORCED TI-6AL-4V ALLOY

Advanced titanium alloy metal matrix composites offer significant mech anical improvements over many conventional materials. In order to mini mize fiber-matrix chemical reactions due to high temperatures involved in the fabrication methods, the final component can be obtained using two different steps: (1) fabrication of preforms (monotapes) by inert plasma spraying and (2) hot pressing of the fabricated preforms. Cont inuous SiC fiber-reinforced Ti-6Al-4V preforms were hot pressed to fab ricate a composite multilayer. Different values of hot pressing proces sing parameters (temperature, applied load, bonding time) were investi gated on the basis of a two-level factorial design. Metallographic and scanning electron microscopy (SEM) analyses were carried out to evalu ate the bonding degree of the fabricated preforms. Preliminary three-p oint bending tests were also performed to understand the mechanical be havior and to show the more suitable values of the processing paramete rs for a hot pressing procedure. These values should be in the range o f 830 to 950 degrees C (temperature), 80 MPa (applied stress), 20 to 3 0 min bonding time to avoid undesired phase transformation, large plas tic flow of the metal matrix, and detrimental chemical reaction at fib er-matrix interface.