Study Of Stirring Ball Milling Of TiH₂/SiC Mixed Powders And Their Sintering Behavior

Ti alloy was used widely because of it’s high specific strength, specific stiffnessand low density （4.505g/cm3）. By refining the grain size of Ti alloy not only offershigher strength, better processablility, but also offers higher strain rate superplasticityor low temperature superplasticity. In this paper, SiC was used as reinforcementparticle. TiH₂/SiC powder with high quality were prepared by Stirring ball milling.Combining with vaccum sintering, the powders’ sintering behavior had beensystematiclly studied on the basis of milling law. This research was expected provide arelatively new process to produce ultra-fine grained Ti alloy with low cost in shortprocess.TiH₂/SiC powders were milled by Stirring ball milling method to study the effect ofmilling time and milling speed on TiH₂/SiC powders’ particle size and size distribution,the sintered samples’ density and microstructure, SiC particle’s morphology anddistribution. The result shows that in the milling speed range of500r/min to700r/min,powder particle size tends to decrease at first and then increase. Under600r/minmilling speed, powder particle size become smaller when increase milling time, sizedistribution become more uniform at the same time. With the increase of milling time,the sample with1.5%SiC which was sintered at different temperature （950℃、1000℃、1050℃、1100℃） in a vacuum atmosphere (1⁵×10^-3Pa) for3h, it’s grain size becomesmaller and more uniform, meanwhile it’s density decrease at first and then increase.In summary, the best milling process is to mill at the speed of600r/min for8h under9:1ball to powder ratio.Compacts were prepared by single-action pressing. By studying the moldingcharacteristics of SiC/TiH₂milled powders, the best forming agent and it’s content wasdetermined at first, then the molding process and debinding process were optimized.The result shows that in the forming agent range of2%to5%, compact density tendsto increase at first and then decrease. In70MPa³50MPa pressure range, compactdensity increases along with the pressure. Too high pressure will lead to have defectsin compact. The final solution is to add4%polyethylene glycol into milled powder asforming agent, add stearic acid as mold lubricant, and then press TiH₂/SiC powderunder150MPa pressure to obtain compact with high quality.The effect of sintering process and SiC content to density and microstructure was studied. The results show that the higher the temperature or sintering time, the higherthe density and the bigger the grain size. With raising the SiC content, the density andthe grain size of the sintered sample will decrease. Considering of the sintered sample’sdensity and it’s grain size requirements,1%SiC content is the best adding amount.When sintered at1050℃in a vacuum atomosphere (1⁵×10^-3Pa) for3h, sample with4.69g/cm^-3density and4μm average grain size can be obtained.