不连续增强镁基复合材料的制备与应用

综述了不连续增强镁基复合材料的制备工艺及特点，介绍了其应用情况，展望了其发展前景。     

Microstructure and Mechanical Properties of Cross-rolled Ti_(50)Ni_(47)Fe_3 Shape Memory Alloy

The microstructures, the phase transformation characteristics, and the mechanical properties of the Ti50Ni47Fe3 alloy in as-forged and as-cross-rolled states were investigated. It is found that, after cross-rolling, the phase transformation temperature (Ms) of the alloy decreases drastically and the grains get refined. Moreover, its yield strength and fracture strength after cross-rolling hit 540 MPa and 687 MPa respectively, up by about 200 MPa over those in as-forged state.     

过渡液相扩散焊连接工艺参数对DD407母材液化的影响

为了将瞬间液相扩散焊的液相形成过程与固相扩散焊复合,充分利用TLP及固相扩散焊的优点,需要研究接头界面处母材液化规律。选用DD407镍基单晶高温合金作为试验材料,中间层合金采用含B为3.5%的BNi9进行TLP连接,观察母材液化宽度和接头宽度在不同工艺参数下的变化。通过分析得到:母材液化区宽度随着加热温度升高及保温时间增长而增加,在焊接温度为1100℃,保温时间为5min,中间层厚度为150μm的情况下,母材液化的宽度达到65.8μm;中间层厚度对母材液化的影响程度相对较大,主要降熔元素B的总量增加;TLP连接过程中,母材液化的过程为降熔元素B不断向母材中扩散,导致母材液化宽度增加,但随着扩散的进行,B元素的含量逐渐降低引起等温凝固,从而在一定程度上影响了表面清理的效果。     

Development of microstructural inhomogeneity in multi-pass flow forming of TA15 alloy cylindrical parts

Revealing the development of microstructural inhomogeneity in the multi-pass flow forming of titanium alloy components is of great significance to the microstructure control and property tailoring. To this end, the microstructural inhomogeneity of TA15 alloy spun cylindrical parts was analyzed based on the deformation history. The results indicate that the material underwent significant compressive strain in the normal direction (ND), tension strain in the rolling and circumferential directions (RD and CD), while tension strain in the CD is slightly small due to the limited material flow in this direction. These strain characteristics make the microstructure, especially the primary α (α_p), present different morphologies in the different planes of the part. Meanwhile, the combined effects of inhomogeneous deformation and temperature distribution in the ND also cause the inhomogeneity of microstructure morphology and parameters in this direction. Quantitative analyses show that with the forming pass increasing, the aspect ratio of α_p increases most in the normal-rolling plane, then in the normal-circumferential plane and least in the circumferential-rolling plane, whereas α_p content decreases in an opposite trend. Along the ND, the aspect ratio and content of α_p is relatively high in the outer and inner surface areas but lowest in the central area, and these inhomogeneous characteristics can be gradually diminished with the forming pass increasing. Furthermore, the variation of hardness inhomogeneity factor indicates that a four-pass forming with the total reduction ratio of 63% could obtain a homogenous microstructure along the ND of the TA15 alloy spun cylindrical part.     

带热障涂层钛合金的蠕变性能

以提高钛合金的抗蠕变性能为目的,在TA32钛合金基体上制备由NiCrAlY黏接层(BC)与氧化钇稳定二氧化锆陶瓷层(TC)组成的热障涂层(TBCs),对带TBCs钛合金抗蠕变性能进行实验与数值模拟研究。结果表明:TA32与TBCs的蠕变速率相差较大,在高温拉伸时TC会对BC和基体的蠕变变形产生明显的约束效应,且TBCs中BC承受的轴向拉伸应力较大。在400 ℃和600 ℃实验温度下,TBCs可将TA32的抗蠕变性能分别提升56%与175%,但当实验温度达到600 ℃、拉伸应力达到200 MPa时,TC发生了严重的开裂与剥落。     

钛合金叶片前缘的外物损伤残余应力数值分析

为研究航空发动机叶片外物损伤(FOD)位置残余应力的分布规律,根据真实叶片前缘特征设计了模拟叶片,基于Johnson-Cook本构模型,使用LS-DYNA软件仿真分析钢珠以不同角度冲击钛合金模拟叶片前缘的过程,对比仿真与相同试验条件下的空气炮模拟外物损伤试验的FOD损伤形貌与宏观尺寸,验证了有限元模型的正确性。提取仿真计算的不同入射角度对应的FOD位置残余应力分布,结果表明:钢珠以0°角入射时,钢珠冲击产生的接触力和变形能明显大于其他入射角度的情况,说明钢珠偏斜一定角度入射时造成的偏斜型缺口处的材料失效与变形不如外物正撞前缘形成的半圆型缺口严重;在FOD缺口底部尖端靠近入射表面区域存在明显的残余拉应力。随着入射角度的增大,残余拉应力区的范围逐渐扩大,残余拉应力最大值逐渐减小。     

钛硼添加剂在铝合金整体结构车轮中的应用

介绍了生产摩托车铝合金整体结构轮时，用钛硼添加剂代替Ａ１－Ｔｉ中间合金的生产试验结果。合金的力学性能稳定，符合要求，在强度值σｂ保持同等水平条件下，伸长率δ５提高２０％～３０％。     

减少铸造Al-Si合金Sr变质潜伏时间工艺研究

Sr变质潜伏时间延长除了给生产带来很多不便外,还会造成Sr烧损增加,变质效果衰退以及铝合金表面氧化-吸氢加剧,对合金造成污染,其中液态金属温度,液态金属的对流强度,Al-Sr合金的几何尺寸及表面状态是影响Sr变质潜伏时间的重要因素。通过建立物理模型,对Sr扩散过程进行流场模拟计算,并进行了试验验证。通过工艺改进,Sr变质潜伏时间由60分钟,缩短至20分钟,变质后合金性能优良,Al-Sr合金取得了良好的变质效果。     

腐蚀条件下LD2航空铝合金裂纹扩展规律研究

 腐蚀损伤会加速飞机结构的疲劳裂纹扩展,缩短飞机疲劳寿命。以LD2航空铝合金材料为研究对象,通过在实验室内模拟飞机服役环境进行加速腐蚀试验,得到不同腐蚀时间下的试验件,并在MTS-810疲劳机上对不同腐蚀时间下的试验件进行疲劳试验,得到不同腐蚀年限下的疲劳断口形貌。通过断口判读分析,得到不同腐蚀年限下的裂纹扩展数据(a,N)。从不同腐蚀时间下的裂纹扩展数据研究分析,得到裂纹长度与循环次数符合指数函数的形式,即裂纹扩展速率与裂纹长度成正比,其斜率依赖于腐蚀损伤与疲劳载荷两个因素,而且在同一应力水平下,其斜率与腐蚀时间呈线性关系,并且其截距与应力水平也呈线性关系。     

火箭贮箱箱底瓜瓣拉深成形数值模拟

基于钣金成形仿真软件,数值模拟了火箭贮箱箱底瓜瓣零件的拉深成形,对瓜瓣拉深模具的拉延筋结构和压边力进行了优化,获得了半圆截面等效拉延筋结构的参数最优组合。