Development of high creep-resistant TiAl-base alloys for directional solidification and measurements of their creep resistance using large-sized specimens

开发用于定向凝固的高抗蠕变 TiAl 基合金并使用大尺寸样品测量其抗蠕变性

基本信息

批准号：
10355026
负责人：
YAMAGUCHI Masaharu
金额：
$ 19.01万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A).
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

项目摘要

Ingots of Ti-47Al alloy with an aligned lamellar microstructure can be grown using a seed of the Ti-43Al-3Si seed alloy. Similarly to the Ti-47Al alloy, seeding should be possible for multi-component alloys based on this alloy if alloying may not cause any significant change in the solidification path of the base alloy. When the alloying elements and the amount of each element to be added to the base Ti-47Al alloy are determined, the Al content of the base alloy is modified to let the relative position of the α/β primary region boundary remain as that is in the binary system. The Al content of the new alloy, C_<AI> can be calculated using the following equation. c_<Al>=47 + aX_<eq> + bY_<eq> + cZ_<eq> +..., where a, b, c and X_<eq>, Y_<eq>, Z_<eq> are the amount and the Al-equivalent of alloying elements X, Y, Z, respectively. When approximately 46 < c_<Al> < 48, the lamellar microstructure can be aligned along the growth direction using a seed of the Ti-43Al-3Si seed alloy at a growth … More rate of 10mm/h.Creep tests were performed in air at 750℃ and 240MPa using specimens with a gauge size of 30 mm in length and 6 mm in diameter cut from directionally solidified ingots. It was found that not only the secondary creep rate but also primary creep strain were reduced by aligning the lamellar boundaries along the loading axis. The secondary creep rate of the binary Ti-47Al alloy under the creep condition is 2.07 x 10^<-9>s^<-1>, which is still comparable to or lower than that reported for the highly alloyed advanced TiAl-base polycrystalline alloys, is much higher than those for the quaternary and quinary alloys. It is of interest to note that the addition of a small amount of Si and transition metals such as Mo, W and Re dramatically increases creep resistance of directionally solidified ingots of TiAl-base alloys. The oxidation resistance of the directionally solidified ingots of Ti-46Al-0.5Si-0.5W and Ti-46Al-0.5Si-0.5Mo alloys is comparable to that of Ti-48Al-2Cr-2Nb, which is one of the most common TiAl-base alloys. However, adding 3% Nb significantly improves oxidation resistance without giving rise to any significant change in the mechanical properties. Less

具有对齐层状微观结构的 Ti-47Al 合金锭可以使用 Ti-43Al-3Si 晶种合金的晶种来生长，与 Ti-47Al 合金类似，如果进行合金化，则基于该合金的多组分合金应该可以进行晶种。不会引起基体合金的凝固路径发生任何显着的变化当添加到基体Ti-47Al合金中的合金元素和各元素的量确定时，基体合金的Al含量为修改以使α/β主区域边界的相对位置保持在二元系统中。新合金的Al含量C_<AI>可以使用以下方程c_<Al>=47+计算。 aX_<eq> + bY_<eq> + cZ_<eq> +...，其中 a、b、c 和 X_<eq>、Y_<eq>、Z_<eq> 是以下物质的数量和 Al 当量分别为合金元素 X、Y、Z。当大约 46 < c_<Al> < 48 时，可以使用 Ti-43Al-3Si 晶种合金晶种以生长速率沿生长方向排列层状微观结构。 10mm/h。蠕变试验在空气中、750℃、240MPa下进行，使用从定向凝固材料上切下的规格尺寸为长度30mm、直径6mm的试样研究发现，通过沿加载轴对齐层状边界，不仅可以降低二次蠕变速率，还可以降低一次蠕变应变，蠕变条件下二元 Ti-47Al 合金的二次蠕变速率为 2.07 x 10^<。 -9>s^<-1>，仍然与报道的高合金先进 TiAl 基多晶合金相当或更低，远高于四元和五元合金值得注意的是，添加少量的 Si 和 Mo、W 和 Re 等过渡金属可显着提高 TiAl 基合金定向凝固铸锭的抗蠕变性能。 Ti-46Al-0.5Si-0.5W和Ti-46Al-0.5Si-0.5Mo合金与Ti-48Al-2Cr-2Nb相当，最常见的 TiAl 基合金之一，但是，添加 3% 的 Nb 可以显着提高抗氧化性，而不会导致机械性能发生任何显着变化。