CAJ | 학술논문

利用二次定向凝固技术控制初凝固β相TiM-Nb合金的片层组织.由于合金定向凝固过程中发生完全包晶转变,在枝晶固液生长界面条件下,即可获得片层方向与生长方向成0°或45°夹角的多孪晶合成晶体(PST).在适当的生长条件下,当片层方向与生长方向平行的片层团在二次定向凝固过程中发生籽晶作用时,可以控制PST晶体内部的片层方向仅与生长方向平行.合金中低含量B的加入会导致非包晶α相的生长,从而不利于控制片层方向.定向凝固TiAl-Nb合金中存在较大的氧化钇颗粒与条状硼化物颗粒,导致其室温拉伸延伸率仅接近2％.
이용이차정향응고기술공제초응고β상TiM-Nb합금적편층조직.유우합금정향응고과정중발생완전포정전변,재지정고액생장계면조건하,즉가획득편층방향여생장방향성0°혹45°협각적다련정합성정체(PST).재괄당적생장조건하,당편층방향여생장방향평행적편층단재이차정향응고과정중발생자정작용시,가이공제PST정체내부적편층방향부여생장방향평행.합금중저함량B적가입회도치비포정α상적생장,종이불리우공제편층방향.정향응고TiAl-Nb합금중존재교대적양화을과립여조상붕화물과립,도치기실온랍신연신솔부접근2％.
The double directional solidification (DS) technique was developed to control the lamellar microstructures in primary βTiAl-Nb alloys.Polysynthetically twinned (PST) crystals with lamellar boundaries parallel to or inclined 45° to the growth direction were achieved due to the complete peritectic transformation during directional solidification of the alloys with the dendritic solid/liquid interface.The PST crystals with aligned lamellar boundaries only parallel to the growth direction were produced when lamellar grains with lamellar boundaries in the same orientation were seeded by themselves under appropriate growth conditions.Low boron addition is harmful to align the lamellar orientation because of the growth of non-peritectic α phase.Due to the larger yttria particles and boride ribbons in the directionally solidified TiAl-Nb alloys,the tensile plastic elongations of the alloys are only close to 2％.