| The Microstructure of material strongly dependent on raw material powders existing morphology which processed by Additive Manufacturing(AM) technology.In order to fabricate TMCs with controlled microstructure and further improve the mechanical properties of materials which made by 3-D printing technology. In this study, The influence of high temperature vacuum tube furnace, microwave heating and sealed fast heating quartz tube method three types of heating treatment on the two kinds of Core-Shell Structure Composites powders micro structure were researched which consisted by TC4/Ti B2 with prismatic form and TC4 /Ti B2 with irregular form. Ti B whiskers reinforced(Ti Bw/TC4) Core-Shell Structure titanium matrix composites powders were successfully fabricated. In this kind of composites powders, Ti Bw are in-situ synthesized In short fibrous, discrete pinning distribution around the surfaces of the TC4 particles.In order to let small particles Ti B2 powder evenly coated on the spherical surface of TC4 particles. low energy milled process parameters were obtained Combined with the laser particle-size distribution measurement, SEM and XRD analysis. Prismatic form Ti B2 powder with coarse granular attached to the TC4 particle surface, while the irregular form Ti B2 powder with compact and smooth surface attached to the TC4 particle surface.Ti Bw reinforcements which grow into the TC4 particle could be observed from the boundry of the composites powders which consisted of TC4 particles and fine prismatic form Ti B2 with the increase of heating temperature and heating rate by the method of high temperature vacuum tube furnace. the boundary of composites powders which consisted by TC4 particles and fine flocculent form Ti B2 were always coated by continuous cell-like structure Ti B. Both Heating temperature and heating speed have little influence to the surface of this kind of composites powders. With the limit of heating and cooling speed, Both kind of two kinds of composites powders appeared sintering phenomenon. It is harmful to the using of the composite powders. Combined the microwave heating results, it could be concluded that high heating speed would promote the growth of Ti B whiskers and discrete pinning distribution around the surfaces of the TC4 particles.Sealed fast heating quartz tube method which is easier to realize industrialproduction of titanium matrix composites powders were systematically investigated.The studied heating temperature and holding time were 1050~1150℃ and 30~480min,respectively. Numbers of Ti B whiskers, with uniform size and 6μm length, arised on the surface of composite powder treated by 1100 ℃ for 120 min. Pinning layer of Ti Bw about 20μm in the thickness were observed at the edge area of the composites powder.Furthermore, it remains constituent phase in the center of powder which form the prospective ideal structure fundamentally. the composites powders which covered by fine flocculent form Ti B2 form continuous cell-like structure Ti B. After heating the composites powders at 1100 ℃ for 120 min, dispersed and fine acicular-like Ti B precipitates were observed on the cross section of composite powder. The Ti B size increased gradually with the increase of holding time.Treating the composites powder which acquire by fast heating quartz tube method with high energy laser, the diameter is 4mm and the power is 1600 W in 10mm/min scanning speed protected in argon, capsule structure titanium composite material were obtained. Ti Bw dispersed in continuous in web like and graded distribution. The feature of the product is the sphere subsrate pinning surrounded by the whisker reinforced phase.microscopic hardness of Titanium matrix composites varies along with Ti B enhancement phase volume fraction in micro area. The HV at the core substrate is about450 lower than the higher dense area of which is range from 510 to 550.Ti B whisker thrust out process were in situ observed and the growing mechanism were investigated. The Ti B whisker of the Cross section micro structure morphology of the composites powders were measured by area ratio according to stereology. Ti B gradient distribution curve and distribute nephogram were obtained, It could be found that the Ti B phase volume fraction showed gradient distribution. The Ti B phase concentration phenomenon exist in the inner region of six kinds of composites powders which produced by By 1050℃ and 1150℃ heat 120 min and 480 min. Using the curve of Ti B enhancement phase volume fraction change with the radial direction.Based on the measured Ti B enhancement phase volume fraction changing curve, the mathematical model of the distribution of Ti B were obtained. which used to calculate Ti B volume fraction and amount of substance in arbitrarily area of composites powders. |
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