摘要
研究了名义成分为Ti-22Al-15Nb的Ti-Al系合金的微观组织和力学性能,以及在准静态和动态加载条件下的变形行为,并对其破坏机理进行了分析。微观组织研究表明,Ti-22Al-15Nb合金铸态组织为等轴晶,晶内主要由α2-Ti3Al相和B2-Ti2AlNb相组成,具有随机取向的片状α2相均匀分布在B2基相上。力学性能研究表明,合金在动态加载条件下表现出较优异的性能,其屈服强度为1 100 MPa,抗压强度为1 750 MPa,且在动态加载下具有更好的塑性。破坏机理分析表明,在准静态加载条件下,合金试样发生剪切破坏,微裂纹首先在α2相及α2相与B2相的相界处萌生,在最大剪应力方向上扩展形成主裂纹,最终导致合金试样破坏;在动态加载条件下,合金的破坏方式为绝热剪切破坏,即在与加载轴呈45°角的方向上形成绝热剪切带,随着应变的增大,裂纹在剪切带中萌生并扩展,最终破坏合金试样。
The microstructure and mechanical properties of Ti-Al based alloy with nominal composition of Ti-22Al-15Nb were investigated,and the deformation behavior under quasi-static and dynamic loading con- ditions was also discussed. The results show that as-cast Ti-22Al-15Nb alloy has equiaxed microstructure mainly composed of α2-Ti3 Al phase and B2-Ti2 AlNb phase, and lamellar α2 phase with random orientation is distributed uniformly in B2 matrix. Investigation on mechanical properties shows that the alloy exhibits higher yield strength of 1 100 MPa and higher compressive strength of 1 750 MPa,and better ductility dur- ing dynamic compression rather than quasi-static compression. Failure mechanism analysis shows that shear failure occurs in the alloy during quasi-static compression,and micro-cracks initiate in α2 phase or the boundary between az phase and B2 matrix and extend along the direction of the maximum shear stress to form main cracks, finally leading to alloy failure. Failure mode of the alloy during dynamic compression is adiabatic shear failure,adiabatic shear bands form at an angle of about 45° with the loading direction,and cracks initiate in the shear band and propagate with the increased strain, finally leading to alloy failure.
出处
《稀有金属与硬质合金》
CSCD
北大核心
2017年第2期45-50,74,共7页
Rare Metals and Cemented Carbides
基金
国家自然科学基金(51571033)
