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Rolling parameters, microstructure control, and mechanical properties of powder metallurgy Ti–44Al–3Nb-(Mo, V, Y) alloy: The impact of rolling temperatures
Intermetallics ( IF 4.4 ) Pub Date : 2020-08-01 , DOI: 10.1016/j.intermet.2020.106817
Mang Xu , Guo-huai Liu , Tian-rui Li , Xiang-long Zhang , Zhao-dong Wang

Abstract Flow softening behavior, microstructure evolution and hot working parameters of powder metallurgy Ti–44Al–3Nb-(Mo, V, Y) alloy were systematically studied by isothermal hot compression. Based on the analysis of processing maps and the corresponding microstructure, power dissipation efficiency peak occurred at two domains, which were associated with dynamic recrystallization (DRX) and super-plasticity. Pile-up of high density dislocation and a large number of twins were the primary deformation mechanisms at low temperature and high strain rate. As the temperature increases, fine DRX grains promote the movement and rotation of grain boundary, the softening of β phase and the transformation of β→α/α2+γ above 1200 °C improve the deformation capacity of the alloy significantly. Crack-free TiAl sheets were successfully obtained by direct hot rolling process at 1080 °C and 1220 °C. The corresponding microstructure and mechanical properties were analyzed. The sheets rolled at 1080 °C was characterized by near γ (NG)+β0 microstructure with a streamline along the rolling direction, while duplex (DP)+β0 microstructure appeared to be the main microstructure at rolling temperature of 1220 °C. The as-rolled sheet exhibits excellent mechanical properties at 800 °C. The sheet rolled at 1080 °C exhibits 320 MPa yield strength and 468 MPa ultimate tensile strength with 142% elongation. The yield strength, ultimate tensile strength, and elongation of the as-rolled sheet are 446 MPa, 586 MPa, and 3.0%, respectively, when rolled at 1220 °C. The excellent ductility of the sample rolled at 1080 °C is attributed to formation of fine DRX grains due to consumption of twins and substructure under tensile stress, which promote grain boundary slip. Lamellar colonies with fine interlamellar spacing and α2 laths formed at 1220 °C can effectively prevent dislocation motion, resulting in a significant increase in the strength of the alloy.

中文翻译:

粉末冶金 Ti-44Al-3Nb-(Mo, V, Y) 合金的轧制参数、组织控制和力学性能:轧制温度的影响

摘要 通过等温热压缩系​​统研究了粉末冶金Ti-44Al-3Nb-(Mo, V, Y)合金的流动软化行为、组织演变和热加工参数。基于对加工图和相应微观结构的分析,功耗效率峰值出现在与动态再结晶 (DRX) 和超塑性相关的两个域中。高密度位错堆积和大量孪晶是低温高应变速率下的主要变形机制。随着温度的升高,细小的DRX晶粒促进了晶界的运动和旋转,1200℃以上β相软化和β→α/α2+γ相变显着提高了合金的变形能力。通过在 1080°C 和 1220°C 的直接热轧工艺成功获得了无裂纹 TiAl 薄板。分析了相应的显微组织和力学性能。在 1080 ℃ 轧制的板材的特征是接近 γ (NG)+β0 组织,沿轧制方向呈流线型,而双相 (DP)+β0 组织似乎是 1220 ℃轧制温度下的主要组织。轧制后的板材在 800 °C 下表现出优异的机械性能。在 1080 °C 下轧制的板材表现出 320 MPa 的屈服强度和 468 MPa 的极限拉伸强度,伸长率为 142%。在 1220 °C 下轧制时,轧制板材的屈服强度、极限拉伸强度和伸长率分别为 446 MPa、586 MPa 和 3.0%。在 1080 °C 轧制的样品具有优异的延展性,这归因于在拉伸应力下由于孪晶和亚结构的消耗而形成细小的 DRX 晶粒,这促进了晶界滑移。1220℃时形成的层间距细的层状菌落和α2板条能有效阻止位错运动,使合金强度显着提高。
更新日期:2020-08-01
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