钛铝合金氢致轧制改性及成形性能研究

With the aerospace and aviation materials developing to low density and high application temperature, Ti-Al alloy becomes an ideal replacing material in place of the high temperature Ni-based alloys. The use of plate is one direction for its practical application. Based on the hydrogen induced plasticity theory, thermo hydrogen processing (THP: hydrogenation-hot, working-vacuum, dehydrogenation) is applied in the rolling and forming processes of Ti-Al alloy plate to increase its plasticity, ductility and hot working ability and control its microstructures and mechanical properties. The main research contents are as follows: 1) the high temperature deformation behaviors and forging process of hydrogenated Ti-Al alloys; 2) the effects of hydrogen addition on the rolling behavior of Ti-Al alloys; 3) the effects of hydrogen addition on the microstructural evolution (phase transformation, dynamic recovery, dynamic recrystallization, dislocation movement and twinning) and the mechanism of hydrogen induced plasticity; (4) determining the optimum rolling process and the optimum hydrogen content of Ti-Al alloys plate; (5) establishing the relativity model between hydrogen content, microstructure and mechanical properties, and achieving the accurate control for microstructure and properties of Ti-Al alloy plate. The research of this project can provide a new method for improvement of plasticity, ductility and hot workability of Ti-Al alloys, propel the application process of Ti-Al alloys, and establish the theoretical basis for the engineering application of thermo hydrogen processing technology.

随着航空航天材料向低密度和高使用温度的方向发展，钛铝合金成为替代镍基高温合金的理想材料，板材的应用是其实用化的一个突破口。针对钛铝合金塑性差、韧性低、热加工困难，本项目基于置氢增塑机理，提出将热氢加工技术（THP：置氢-热加工-真空除氢）应用于钛铝合金板材轧制及成形过程中，以改善其塑韧性和加工性能，实现对其组织和性能的精确调控。主要研究：1）置氢钛铝合金高温变形行为及开坯锻造工艺研究；2)氢对钛铝合金板材轧制及成形性能的影响规律；3)氢对钛铝合金组织结构演变（相变、动态回复、动态再结晶、位错运动和孪晶等）的影响规律及其机理分析；4)制定钛铝合金板材轧制的最佳氢含量及最佳成形工艺方案；5)建立钛铝合金板材氢含量与组织结构和性能的相关性模型，实现板材组织和性能的精确调控。本项目的研究将为提高钛铝合金的塑韧性、改善其加工性能、推进其实用化进程提供一条新途径，为热氢加工技术的应用奠定理论基础。

Ti-Al合金密度低、高温力学性能优良，在航空航天工业中展现出令人瞩目的发展前景。但其本征脆性、热加工能力差严重限制了它的工程应用，因此本项目基于置氢增塑机理，提出将热氢加工技术应用于钛铝合金板材轧制及成形过程中，以改善其塑韧性和加工性能。本项目研究了置氢Ti-Al合金的高温变形行为，建立了置氢Ti-Al合金高温变形本构关系；提出了氢致扩散层片分解机制和氢致相变层片分解机制，阐明了氢致动态再结晶机制；研究了置氢Ti-Al合金铸锭开坯锻造工艺，获得了晶粒均匀细小的板坯，阐明了板坯初始组织及退火热处理之间的关系；研究了板材轧制性能与氢含量、轧制参数（轧制温度、道次变形量和总变形量）之间的关系，揭示了板材热轧过程中的氢致改性机理。研究发现，置氢可以降低Ti-Al合金锻造温度约50℃，氢致峰值应力平均下降率约为25%，合金热加工窗口增大，并可获得细小均匀的组织。置氢后Ti2AlNb合金板材热成形塑性提高约一倍，载荷降低最大达50%，成形性能提升明显。因此，本项目的研究为热氢加工技术在Ti-Al合金热加工领域的应用奠定了理论基础，为提高Ti-Al合金的塑韧性、改善其加工性能、推进其实用化进程提供一条新途径，具有重要的理论和工程意义。