## 3 Results and Discussion
Figure 2: The relationship between shear rate and viscosity of the feedstocks prepared from blended and prealloyed powders. the reaction between Ti and Al becomes intense and results in an exothermic peak in the DSC curve. The TG and DSC results are subsequently used to design a thermal debinding and sintering schedule, which is shown in Figure 5. During thermal debinding, the binders become soft and the viscosity is reduced. To avoid the distortion from the viscous creep, a relatively low heating rate of 3 \({}^{\circ}\)C/min is used during thermal debinding. According to the two-stage weight loss process shown in the TG curve (Figure 4), the samples are isothermally held at two different temperatures (400 \({}^{\circ}\)C for 30 min and 500 \({}^{\circ}\)C for 60 min) to ensure adequate decomposition of the binders. The thermally debound samples are subsequently heated to the sintering temperature with a rate of 5 \({}^{\circ}\)C/min. After sintering, the as-sintered parts are cooled to 500 \({}^{\circ}\)C with a controlled rate of 5 \({}^{\circ}\)C/min and then cooled to room temperature in the furnace. Figure 6 shows the green and as-sintered tensile bars. Figure 7 shows the stress-strain curves of B and P samples sintered at 1200 \({}^{\circ}\)C for 180 min and 1300 \({}^{\circ}\)C for 120 min. Table 2 summarizes the impurity contents, densities, and mechanical properties of the specimens sintered in different conditions. The B samples sintered at 1200 \({}^{\circ}\)C for 180 min have a density of 4.26 g/cm\({}^{3}\), yield strength of 810 MPa, ultimate tensile strength (UTS) of 927 MPa, and elongation of 4.6%. For comparison, the P samples sintered at 1200 \({}^{\circ}\)C for 180 min have a density of 4.26 g/cm\({}^{3}\), yield strength of 818 MPa, UTS of 928 MPa, and elongation of 5.2%. The density and mechanical properties of the B samples are similar to those of the P samples although the elongation of B samples is a little bit lower. However, when B and P samples are sintered at 1300 \({}^{\circ}\)C for 120 min, the mechanical properties deteriorate. The oxygen content increases when samples are sintered at  
Figure 4: (**a**) TG curves of polyethylene (PE), paraffin wax (PW), ethylene vinyl acetate (EVA), polyformaldehyde (POM) and stearic acid (SA) with a heating rate of 10 \({}^{\circ}\)C/min; (**b**) TG and DSC curves of a green sample prepared from blended powder with a heating rate of 10 \({}^{\circ}\)C/min. Figure 5: The schedule of thermal debinding and sintering. 1300 \({}^{\circ}\)C while the carbon content and nitrogen content are consistently controlled to 0.07-0.08 wt% and -0.03 wt%, respectively. Figure 8 shows the fracture surfaces of B and P samples sintered at 1200 \({}^{\circ}\)C for 180 min and 1300 \({}^{\circ}\)C for 120 min. The fracture of all the samples exhibits big cavities (white arrow A), fine dimples (white arrow B), and a few cleavages (white arrow C). The cavities derive from the separation of grains, indicating that the metallic bonding between the grains is not well-established. When the sintering temperature increases from 1200 \({}^{\circ}\)C to 1300 \({}^{\circ}\)C, the number of the cavities in the fracture surface decreases. The fine dimples imply ductile fracture of the specimens upon the tensile test, while the presence of cleavage feature indicates some grains fracture in brittle mode. Hence, the fracture mechanism of sintered B and P samples has a mixed (intergranular and transgranular) mode.