置氢TC16钛合金微观组织与变形行为

通过置氢处理得到不同氢含量的TC16钛合金,采用连续升温法研究了氢含量对TC16钛合金相转变温度的影响,利用光学显微镜研究了置氢TC16钛合金的微观组织,应用准静态压缩试验研究了置氢TC16钛合金的变形行为,通过磁脉冲冷镦试验研究了高应变速率下合金的变形行为。结果表明,TC16钛合金相变温度随氢含量的增加而单调递减,当氢含量达到0.30wt.%时,相变温度大约下降150℃；置氢TC16钛合金微观组织发生变化,低氢时出现了马氏体组织,高氢时主要由等轴β相组织构成；置氢TC16钛合金的应变速率敏感性增加,随着变形速率的提高,其变形性能得到改善,在高应变速率条件下压缩变形极限大于86%,通过冷镦试验制备了表面完好的托板螺母,对变形行为进行了验证。     

置氢0.11%Ti-6Al-4V合金超塑变形行为及其机制

研究了置氢0.11%的Ti-6Al-4V在800～900℃温度范围和3×10(-4)～1×10(-2)s(-1)应变速率范围内的超塑变形行为,应用光学显微镜研究了变形过程中的组织演变.结果表明:置入0.11%的氢能够显著改善Ti-6Al-4V超塑变形行为,峰值应力较原始合金降低了15～33 MPa,应变速率敏感性指数m值提高至0.497,变形激活能为322 kJ·mol(-1);在840～860 ℃温度范围和3×10(-3)～1×10(-3)s(-1)应变速率范围内,具有最佳超塑性,其延伸率最高达到1530%.0.11%的氢使α相及β相软化的同时促进了动态再结晶,提高了位错的攀移能力并且降低了位错密度;α和β两相比例未发生显著变化,适当的比例在变形过程中有利于两相相互抑制长大.置氢后超塑变形机制与未置氢相同,主要为界面的滑动和晶粒的转动,而位错的运动及动态再结晶为其协调机制.     

温热条件对7B04铝合金性能的影响

针对高强铝合金航空复杂构件室温成形难问题,通过电阻炉加热及冲压成形试验探究了温热条件对7B04铝合金硬度及成形性能的影响规律,通过差示扫描量热仪及透射电镜探讨其性能变化机理。研究结果表明：7B04铝合金加热后,升温速率越快,材料硬度下降越快;在400 ℃以上炉温条件下加热较长时间,硬度会先降后升;在200~450 ℃温度范围内,7B04板材冲压成形性能随出炉温度提高而提高,加热至400 ℃以上出炉冲压成形效果较好,升温速率的提高可以使7B04铝合金在硬度降幅相同的情况下,达到更高的成形温度,获得更好的成形性能。     

置氢Ti-6Al-4V合金组织演变及其对切屑形成的影响

利用金相显微镜、X射线衍射仪和SEM对置氢Ti-6Al-4V合金材料微观组织及切屑形貌进行了观察分析,通过室温压缩实验测试置氢钛合金力学性能,探讨了置氢Ti-6Al-4V组织、力学性能与切屑形态之间的联系,研究了置氢Ti-6Al-4V合金组织演变及其对切屑形成的影响.结果表明:氢含量为0.6wt%时,钛合金置氢炉冷后组...     

Influence of thermo hydrogen treatment on hot deformation behavior of Ti600 alloy

Hot compressive deformation of Ti600 alloy after thermo hydrogen treatment (THT) was carried out within hydrogen content range of 0-0.5%, temperature range of 760-920 ℃ and strain rate range of 0.01-10 s-1. The flow stress of Ti600 alloy after THT was obtained under hot deformation condition, and the influence of hydrogen on work-hardening rate (S*), strain energy density (U*), and deformation activation energy (Q) was analysed. The results show that the flow stress of Ti600 alloy decreases remarkably with the increase of hydrogen when the hydrogen content is less than 0.3%. Both S* and U* decrease with the increase of hydrogen when the hydrogen content is less than 0.3%, and when the hydrogen content is more than 0.3%, S* and U* increase with hydrogen addition. The value of Q decreases with the increase of strain at the same hydrogen content. The addition of small quantity of hydrogen leads to an increase of Q at small strain values, and when the strain reaches 0.6, the value of Q decreases gradually with the increase of hydrogen. When the hydrogen content is within the range of 0.1%-0.3%, the flow stress of Ti600 alloy is decreased when being deformed at the temperature range of 760-920 ℃.     

Influence of hydrogenation on microstructures and microhardness of Ti6A14V alloy

The microstructures of Ti6A14V alloy after hydrogenation were investigated by optical microscopy（OM）, X-ray diffraction（XRD） and transmission electron microscopy（TEM）. The influence of hydrogenation on the hardness of α and β phases was analysed by microhardness testing. The influence of hydrogenation on alloying elements diffusion was studied by electron probe microanalysis（EPMA）. The microstructural observation reveals that hydride δ （FCC structure） as well as large number of dislocations precipitate in the specimens with 0.278% and 0.514% hydrogen, and a lot of twins are found in the specimen with 0.514% hydrogen, simultaneously. The result of microhardness testing shows that the hardness of a and β phases increases synchronously with the increase of hydrogen and the hardness increment of β is larger than that of a. According to analysis of EPMA, the diffusion ability of alloy elements Al and V increases after hydrogenation. It is considered that hydrogen solution strengthening and V element diffusion are the main factors causing the hardness of a phase increase with the increase of hydrogen, and the formation of δ hydrides, lattice defects, hydrogen solution strengthening and Al element diffusion jointly cause the hardness of β phase increase with the increasing hydrogen.     

热压工艺对SiC纤维增强TB8复合材料组织影响研究

通过箔-纤维-箔法制备了Si C纤维增强TB8复合材料,采用光学电子显微镜(OM)、扫描电镜(SEM)和电子探针(EPMA)对复合材料的微观组织进行表征与分析,研究了真空热压复     

TA32钛合金板成形性能与电磁辅助弯曲成形实验研究

由于TA32钛合金板室温成形性差、精度难以保证,开展了电磁辅助弯曲成形方法的实验研究,通过拉伸和电磁成形实验探究了TA32钛合金的力学性能和成形性能,获得了TA32钛合金板在准静态和动态拉伸下的应力、应变关系,给出了在电磁成形状态下的成形极限应变,阐明了电磁成形作用下的TA32钛合金的增塑机制。采用匀压式电磁辅助弯曲成形的方法对TA32钛合金板开展实验研究,结果表明:电磁辅助弯曲成形方法能够有效地提高弯曲件的成形精度,并且在一定条件下,放电能量越高,贴模效果越好、成形精度越高。带压紧翼的弯曲件的变形区外层过度伸长而产生减薄并开裂,不带压紧翼的弯曲件通过合理地控制放电电压能够获得较好的成形效果。     

等轴组织TC21合金高温变形本构模型和热加工图

对等轴组织TC21合金在Gleeble-1500热模拟实验机上进行了等温压缩实验,变形温度为760、800、840、880、920和960℃(α+β相区),应变速率为0.001、0.01、0.1、1和10.0 s-1.结果 表明:TC21合金的流动应力随应变速率降低和变形温度升高而降低;随应变的增加,变形激活能从570 kJ·mol-1减少到410 kJ· mol-1.基于应变补偿的Arrhenius方程建立TC21合金高温变形本构模型,该模型可以精确地预测流动应力随工艺参数的变化.基于动态材料模型建立了TC21合金的热加工图;热加工图中的能量耗散效率和非稳态成形区域随着应变增加而改变.