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利用冷坩埚定向凝固技术制备Ti-46Al-6Nb(摩尔分数,%)合金,然后对定向凝固铸锭进行热处理,热处理温度为1330°C,热处理区间在α相单相区。研究热处理前后铸锭显微组织和力学性能的变化。结果表明:铸锭经过热处理后,大的柱状晶转变为等轴晶。随着热处理循环次数的增加,晶粒尺寸减小,这是由于发生了再结晶和小片层的大晶粒与大片层的小晶粒之间的转变。四次循环热处理能够有效地细化晶粒尺寸,使晶粒尺寸从1.33 mm降低到0.59 mm,然而片层间距从0.71μm增加到1.38μm。延长保温时间和增加热处理循环次数能够消除晶粒间和片层间的β偏析相。压缩实验结果表明,对定向凝固铸锭,平行于柱状晶生长方向的压缩强度为1385.09MPa,垂直于柱状晶生长方向的压缩强度为1267.79 MPa;铸造试样的压缩强度为1180.64 MPa,经热处理循环两次后压缩强度提高到1449.75 MPa,热处理循环4次后压缩强度提高到1527.76 MPa。循环热处理后,合金试样的断裂方式为准解理断裂。
Ti-46Al-6Nb (mole fraction,%) alloy was prepared by cold crucible directional solidification technique, and then the directional solidification ingot was heat-treated at a temperature of 1330 ° C and a heat treatment zone in the α phase single phase region. The changes of microstructure and mechanical properties of ingot before and after heat treatment were studied. The results show that after the ingot is heat treated, the large columnar crystals transform into equiaxed grains. As the number of heat treatment cycles increases, the grain size decreases due to recrystallization and the transition between large grains and small grains of the large lamella. Four cycles of heat treatment can effectively refine the grain size, reducing the grain size from 1.33 mm to 0.59 mm, while increasing the sheet spacing from 0.71 μm to 1.38 μm. Extending the holding time and increasing the number of heat treatment cycles can eliminate the β-segregation phase between the grains and between the layers. The results of compression experiments show that the compressive strength parallel to the columnar crystal growth direction is 1385.09MPa, the compressive strength perpendicular to the columnar crystal growth direction is 1267.79MPa, the compressive strength of the cast sample is 1180.64MPa, and the heat treatment cycle After two compressive strength increased to 1449.75 MPa, heat treatment cycle after four compressive strength increased to 1527.76 MPa. After cyclic heat treatment, the fracture mode of the alloy sample is quasi-cleavage fracture.