| Low plastic of Ti Al based alloy is one of hinder to application, but less comparisons and depth study about impact of plastic. In this paper, macrostructure, microstructure, and mechanical properties of Ti-48Al-2Cr-2Nb alloy using graphite mold, pemanent mold, ceramic mold have been comparative studied. Based on improving plastic of Ti-48Al-2Cr-2Nb alloy, heat treatment processes were designed, and the influence on structure and mechanical properties were studied.Resultes showed that: columnar crystals of cross-section of rectangular samples are grown in the opposite direction, final solidification line of sample using graphite mold is the longest, the followed is pemanent mold, ceramic mold is the shortest; phases composition of as-cast are ?-Ti Al??2-Ti3 Al and B2, the microstructure is mainly consist of lamellar ?-Ti Al, mechanical properties for the three kinds of mold have no significant difference.The hot isostatic pressing process commonly used for titanium alloy can not eliminate all shrinkages and other defects of Ti Al based alloy. But the process designed in this paper, 1160?/130MPa/3h, can eliminate all shrinkages and other defects of Ti Al based alloy. phase composition are same with as-cast, but microstructure morphology changed from lamellar to block and ?2 changed from block to distribution along ? grains boundries, block B2 of as-cast disappeared, dispersed B2 observed at room temperature.A hot isostatic pressing+quenching-tempering-short term high temperature treatment process was designed, a refinement near lamellar microstructure was obtained, and the mechanical properties of the alloy using graphite mold was improved.A integrity small size blade with good internal and external quality can be obtained using Y2O3 ceramic mold. |
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