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在NiTi合金中添加少量Al、Nb、Hf强化元素,采用定向凝固原位自生法制备了一种NiTi基自生复合材料,并在950℃对定向凝固棒分别进行了12h、50h及100h的均匀化热处理,对热处理后的试样进行了室温抗拉强度测试。结果表明,定向凝固组织为沿[001]方向生长的细小的棒状胞晶组织,β-Nb相和Ti2Ni相增强体颗粒沿NiTi胞晶间的[001]方向排列。随热处理时间的延长,胞晶尺寸逐渐粗化,两增强相粒子分布更加弥散均匀。热处理后NiTi基自生复合材料的最大抗拉强度达到1972MPa,超过了4130和8640超高强度钢,与4140和4340超高强度钢的强度基本相当,达到或超过了多种国内外现役的超高强度钛合金。
A small amount of Al, Nb and Hf strengthening elements were added into the NiTi alloy and a NiTi-based in-situ composite was prepared by directional solidification in situ. The directional solidified rods were homogenized at 950 ℃ for 12h, 50h and 100h, respectively Heat treatment, heat treated specimens at room temperature tensile strength test. The results show that the directionally solidified microstructure is a small rod-like cell structure grown along the [001] direction. The β-Nb phase and Ti2Ni phase reinforcing particles are arranged along the [001] direction between NiTi cells. With the extension of heat treatment time, the cell size gradually coarsens and the distributions of two enhanced phase particles disperse more evenly. The maximum tensile strength of NiTi-based in-situ composites after heat treatment reached 1972MPa, surpassing that of 4130 and 8640 ultrahigh strength steel, which is almost the same as the strength of 4140 and 4340 ultrahigh strength steel, meeting or exceeding the requirements of many ultra-high strength Strength of titanium.