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摘要
Effects of trace TiB2 addition on the solidification microstructure of Ti-48A1-2Cr-2Nb + (0.18, 0.54, 0.9) wt.% TiB2 alloys were investigated by arc melting and electromagnetic levitation melting in this paper. Results showed that the matrix alloy generated a large-grained (similar to 800 mu m) fully lamellar microstructure, and the grain size decreased with increasing TiB2 additions. With 0.18 wt.% TiB2 addition, the grains remained fully lamellar, at about 700 pm in diameter. For more TiB2 addition (0.54 wt.%), grain size decreased to an average value of 200 pm. The grain refinement could be explained by constitutional undercooling and alpha phase nucleation on the beta laths of secondary TiB2/beta borides. With 0.9 wt.% TiB2, the alloy melt produced primary TiB2 crystals during solidification to nucleate beta grains. The beta grains in turn nucleated and were transformed to et grains with the generation of secondary TiB2 flakes. This resulted in equiaxed, refined (similar to 200 mu m) lamellar grains without element segregation. The elimination of element segregation could be attributed to the fine equiaxed dendrites, corresponding to the result of electromagnetic levitation melting quenching experiments. With equivalent B additions, the grain refinement effect was equal, except for the cavity defects.
- 出版日期2015-8
- 单位哈尔滨工业大学
