一类易变形的含锰β凝固γ-TiAl合金热物性参数分析

Analysis on the Thermo-physical Properties of a kind of Deformable Mn-containing β-solidifying γ-TiAl Alloys

摘要:

材料的导热和膨胀性能是影响其应用的重要因素，本文以低成本、易变形的Ti-42Al-5Mn合金（原子分数，下同）为研究对象，研究了钨、硼微合金化对合金的热扩散速率、热导率、热膨胀性等热物性参数的影响。结果表明，随着W含量提高至1.0 at.%，合金的热扩散率稍有降低，反之B含量提高至0.3 at.%，合金的热扩散率略有增加。W添加降低合金导热性能与其增加组织中βo相含量有关。对于β凝固γ-TiAl合金，γ、α2、βo三相导热能力大小顺序应为γ＞α2＞βo。而B提高合金的导热性能与B在合金中形成的含B第二相粒子有关。W对合金线热膨胀性影响较小，在100~300℃范围内，随着W含量提高至1.0 at.%，合金的平均线膨胀系数稍有降低，相反在更高温度时的影响逐渐减小。TiAl合金的热膨胀系数数值与铸铁相当，低于钢铁、镍基高温合金等材料，在制造诸如活塞这类要求热膨胀系数很低的部件时具有一定的应用价值。

Abstract:

The thermal conductivity and expansion properties of materials are important factors affecting their application. The effects of W, B addition on the thermo-physical properties such as thermal diffusion rate, thermal conductivity and thermal expansion of Ti-42Al-5Mn alloy (at.%, the same below) with low cost and good hotworkability were systematically studied. The results show that, with the increase of W content to 1.0 at.%, the thermal diffusivity of the alloy decreases slightly, on the contrary, after the B content increases to 0.3 at.%,that of the alloy increases slightly. The promotion of βo phase in microstructure by W addition is the main reason for decreasing the thermal conductivity of the alloy. It is observed that these phases in β-solidifying γ-TiAl alloys are followed by γ, α2, and βo in deceasing order of thermal conductivity. On the other hand, B improving the thermal conductivity of the alloy might be related to the B-containing precipitates in the alloy. W addition (0.5~1.0 at.%) has little effect on the average linear expansion coefficient of Ti-42Al-5Mn alloy. In the range of 100 ~ 300 ℃, with W content increase to 1.0 at.%, the average linear expansion coefficient of the alloy decreases slightly, on the contrary, the influence decreases gradually at higher temperature. The thermal expansion coefficient of TiAl alloy is equivalent to that of cast iron, and lower than that of steel, nickel base superalloy and other materials. It would have certain application value in components requiring very low thermal expansion coefficient such as piston.