Ti和Al的交互作用对Nb-Ti-Si-Al合金微观组织和力学性能的影响

Study of Ti and Al interaction on microstructures and mechanical properties of the Nb-Ti-Si-Al alloys

摘要:

Nb-Si基超高温合金由于具有低密度和高熔点,有望取代当前先进的Ni基高温合金,成为新型的高温结构材料。Ti和Al均为对Nb-Si基合金有益的合金化元素。在文献中,通常对低含量(≤ 3 at. % )Al进行合金化研究,在此情形下不会出现Nb-Al金属间化合物相。Nb-Al金属间化合物中Nb₃Al和Nb₂Al具有良好的强度和抗蠕变性能,NbAl₃则是重要的高温结构材料,而目前公开文献中关于Nb-Si基合金中含有Nb-Al金属间化合物的报道较少。因此,本文重点关注高Al含量对合金中Nb-Al金属间化合物形成的影响,研究两个高Al含量的Nb-Ti-Si-Al合金(A2: Nb-18Ti-14Si-9Al、A4: Nb-21Ti-14Si-9Al)的微观组织和力学性能,其中设计A4合金是为了分析Ti含量变化的影响。A2合金由(Nb)、Nb₅Si₃和Nb₃Al三相组成,而A4合金由(Nb)和Nb₅Si₃两相组成。A2和A4合金的室温断裂韧性分别为11.1 MPa.m_1/2和10.9 MPa.m_1/2,同时对两个合金进行微压痕测试,以表征合金在微观尺度的力学性能。

Abstract:

Nb-Si based alloys show great promise to surpass current advanced Ni-base superalloys due to their low densities and high melting points. Both Ti and Al are beneficial alloying elements for Nb-Si based alloys. In the literature, small amount (≤ 3 at. % ) of Al have frequently examined, and Nb aluminides are usually not formed in this case. Since Nb₃Al and Nb₂Al have good strength and creep properties, NbAl₃ is also a candidate hot-section material, and the study of Nb-Si alloys with these possible Nb alumininides is lacking, so we focus our efforts on primarily whether Nb aluminide is formed or not by adding more Al in the as-cast Nb-Ti-Si alloys. This work studied the microstructures and mechanical properties of two Nb-Ti-Si-Al alloys (A2: Nb-18Ti-14Si-9Al, A4: Nb-21Ti-14Si-9Al) with higher Al content, and the A4 alloy was designed to examine the alloying effect of more Ti. The A2 alloy consists of (Nb), Nb₅Si₃ and Nb₃Al, while the A4 alloy is composed of (Nb) and Nb₅Si₃. The comparable fracture toughness of the A2 alloy and the A4 alloy is 11.1 MPa.m_1/2 and 10.9 MPa.m_1/2, respectively. Moreover, the indention experiments are employed to characterize the micro scale mechanical properties of these Nb-Ti-Si-Al alloys.