一种新型易变形Ti-Al-Mn-W合金组织与力学性能

Microstructure and Mechanical Properties of a Novel Deformable Ti-Al-Mn-W alloy

摘要:

设计并制备了一种新型低成本、易变形的Ti-43Al-3.5Mn-0.5W（原子百分数，下同）合金锻锭，并对其组织、室/高温拉伸力学性能、抗高温氧化性、热变形能力进行了系统分析。结果表明，与Ti-42Al-5Mn相比，研制的合金强度、抗高温氧化性、热变形能力更佳，且该合金α2和βo相中具有更低的Mn含量，降低了合金近服役温度下富锰Laves相的析出倾向。合金的固态相变路线为：β→β+α→β+α+γ→β+βo+α+α2+γ→βo+α2+γ，其中γ相完全熔解的温度（Tγ-solv）约为1250℃，β单相区温度（Tβ或Tα）约为1360℃。热处理后合金显微组织为片层和片层界面处大量βo和γ混合相。通过两步热处理，锻态合金的高温强度和稳定性均有一定提升，这主要归结为片层组织含量的提高和片层晶团尺寸的细化。1260℃/30min/AC+800℃/3h/FC热处理合金800℃的屈服强度、抗拉强度和延伸率分别为320 MPa、555MPa、16%。

Abstract:

A novel deformable Ti-43Al-3.5Mn-0.5W (at.%, the same below) alloy was designed and fabricated. The microstructure characterization, room and elevated temperature tensile mechanical properties, anti-oxidation resistance, and deformation capacity were investigated. The results indicate that compared with Ti-42Al-5Mn, the developed alloy has better strength, high temperature anti-oxidation resistance and thermal deformation ability. The α2 and βo phases of the novel alloy have lower Mn content, which reduces the precipitation tendency of Mn-rich Laves phase at near service temperature. The evolution of the phases in the alloy can be generalized as follows: β→β+α→β+α+γ→β+βo+α+α2+γ→βo+α2+γ, with the Tγ-solv≈1250℃, Tβ≈1360℃. The microstructure of the alloy after heat treatment is lamellar structure and a large number of βo and γ mixed phases at the lamellar interface. Through two-step heat treatment, the high temperature strength and stability of the forged alloy are improved to a certain extent, which is mainly attributed to the increase of lamellar structure content and the refinement size of lamellar colonies. At 800℃, the yield strength, tensile strength, and elongation of the forged alloy treated with 1260℃/30min/AC+800℃/3h/FC were 320 MPa, 555 MPa, and 16%, respectively