Ti-6Al-4V合金超塑性变形时的组织演化

利用光学显微镜和扫描电镜对超塑性拉伸后的细晶Ti-6Al-4V合金分别进行了断口形貌分析和组织演化规律研究。结果表明:细晶Ti-6Al-4V合金室温拉伸时,断裂方式为准解理断裂;超塑性拉伸时,试样断裂的主要形式是韧窝-空洞聚集型断裂。在初始应变速率不变的条件下,随着拉伸温度的升高,α相晶粒尺寸增大,β相数量增多,空洞数量减少,且在840℃至930℃拉伸时,α相晶粒仍保持等轴状态,但在较高温度(960℃)拉伸时,α相晶粒被拉长,部分区域出现网篮组织。在拉伸温度不变时,随着初始应变速率的降低,α相晶粒尺寸增大,β相增多,空洞数量减少。高温(960℃以上)拉伸时,β相颗粒具有良好的塑性和较低的硬度,丰富的β相有利于晶界协调滑动,并对空洞的产生具有抑制作用。     

细晶1420铝锂合金超塑性能试验研究

文章以采用双级时效制度和转向轧制工艺制备的细晶1420铝锂合金为研究对象,通过恒应变速率超塑拉伸试验,研究了合金的单轴超塑拉伸性能。结果表明,在460℃~520℃温度条件下和1×10-4s-1~5×10-3s-1应变速率范围内,细晶1420铝锂合金表现出良好的超塑性,在温度460℃、应变速率1×10-4s-1条件下,延伸率达到650%。利用光学显微镜和透射电镜等检测手段,对超塑变形后材料的组织进行了观察和分析。     

生物医用Ti-29Nb-13Ta-5Zr合金的超塑性行为

采用拉伸速率突变法,研究Ti-29Nb-13Ta-5Zr(Ti-29-13)合金冷轧后在700~800 ℃和5′10-4~1′10-2 s-1应变速率范围内的高温变形行为和变形机制,并与典型β钛合金Ti-15V-3Cr-3Sn-3Al(Ti-15-3)进行比较。结果显示两种合金中均出现了非连续屈服现象,Ti-29-13合金的亚晶行为不同于Ti-15-3合金。Ti-29-13合金的延伸率低于Ti-15-3合金,应力指数n几乎恒定为3.3,变形激活能为152~161 kJ/mol;Ti-15-3合金在730 ℃以上的n值为2.3~2.5,变形激活能为173~176 kJ/mol。     

Effect of minor Sc and Zr on superplasticity of Al-Mg-Mn alloys

The effect of Sc and Zr on the superplastic properties of Al-Mg-Mn alloy sheets was investigated by control experiment. The superplastic properties and the mechanism of superplastic deformation of the two alloys were studied by means of optical microscope, scanning electronic microscope and transmission electron microscope. The elongation to failure of Al-Mg-Mn-Sc-Zr alloy is larger than that of Al-Mg-Mn alloy at the same temperature and initial strain rate. The variation of strain rate sensitivity index is similar to that of elongation to failure. In addition, Al-Mg-Mn-Sc-Zr alloy exhibits higher strain rate superplastic property. The activation energies of the two alloys that are calculated by constitutive equation and linear regression method approach the energy of grain boundary diffusion. The addition of Sc and Zr decreases activation energy and improves the superplastic property of Al-Mg-Mn alloy. The addition of Sc and Zr refines the grain structure greatly. The main mechanism of superplastic deformation of the two alloys is grain boundary sliding accommodated by grain boundary diffusion. The fine grain structure and high density of grain boundary, benefit grain boundary sliding, and dynamic recrystallization brings new fine grain and high angle grain boundary which benefit grain boundary sliding too. Grain boundary diffusion, dislocation motion and dynamic recrystallization harmonize the grain boundary sliding during deformation.     

大晶粒FeAl合金超塑性变形的显微组织演变和变形激活能

本文对大晶粒ＦｅＡｌ金属间化合物塑性变形的微观组织演变进行了研究，并测定了其超塑性变形激活能，显微组织分析表明，合金的超塑性变形是一个晶粒变形，内部形成亚晶界，进而亚晶界向晶界转换，从而使晶粒得以细化的过程，Ｆｅ－３６．５Ａｌ，Ｆｅ－３６．５Ａｌ－１Ｔｉ和Ｆｅ－３６．５Ａｌ－２Ｔｉ合金变形激活能的测定值分别为３７０，２９０和２６０ｋＪ．ｍｏｌ＾－１大大低于其他的ＦｅＡｌ基合金蠕变激活能，表明超塑性     

Microstructure evolution and low temperature superplasticity of ZK40 magnesium alloy subjected to ECAP

Microstructure evolution and superplastic behaviors of ZK40 magnesium alloy were investigated in the temperature range of 473–623 K. Transmission electron microscopy (TEM) was used to study the microstructure changes. After the alloy had been processed by equal channel angular pressing (ECAP) for one pass through the die, significant twinning was found to have occurred, and the mean grain size was 5.6 μm. Finer grains were obtained after multi-pass ECAP, and the average grain size of the alloy ECAPed for three passes was as low as 0.8 μm; this alloy exhibited low temperature superplasticity at 473–523 K, and the elongations obtained at the initial strain rate of 1×10⁻³ s⁻¹ were 260% at 473 K and 612% at 523 K. Corresponding values for the ZK40 alloy processed by ECAP for only one pass were 124% at 473 K and 212% at 523 K. Poor superplastic behavior of the ZK40 alloy processed by ECAP for only one pass was related to the longrange stresses associated with the non-equilibrium grain boundaries within the coarse grains. The incompatibility between the fine grains and the coarse grains was thought to be unfavorable to the improvement of superplascity. This article is based on a presentation in “The 7th Korea-China Workshop on Advanced Materials” organized by the Korea-China Advanced Materials Cooperation Center and the China-Korea Advanced Materials Cooperation Center, held at Ramada Plaza Jeju Hotel, Jeju Island, Korea on August 24–27, 2003.     

沙漏挤压镦粗复合加工技术

本文研究了一种新的晶粒细化方法 :沙漏挤压工艺。这种工艺是在一定温度下通过对材料进行反复挤压产生大的塑性变形 ,同时进行动态再结晶而使材料得到细化。本文对铸态 Zn- Al合金进行了实验 ,初步研究了沙漏挤压工艺对于材料组织和性能的影响。实验结果表明 :沙漏挤压工艺能够有效的细化晶粒 ,使材料获得均匀的等轴细晶组织和优良的综合性能 ,并有助于实现高应变速率超塑性     

2A97 铝锂合金超塑变形规律及其本构方程

目的研究2A97铝锂合金在390~470℃温度范围和3×10-4~3×10-2s-1应变速率范围内的超塑变形行为,揭示温度和应变速率对延伸率和峰值应力的影响规律,并建立超塑拉伸变形本构方程。方法采用单轴超塑拉伸试验方法进行研究。结果当变形应变速率低于3×10-3s-1时,2A97铝锂合金真应力-真应变曲线呈现稳态流变特征;当应变速率高于3×10-3s-1时,则呈现软化特征。在450℃,应变速率为1×10-3s-1条件下,达到最大延伸率600%。结论 2A97铝锂合金具有良好的超塑变形性能,其应变速率敏感性指数m平均值为0.35,超塑变性激活能Q值为145.87 k J/mol,远高于纯铝自扩散激活能65.6 k J/mol,表明此时铝锂合金变形机制仍以晶内滑移为主。     

陶瓷超塑性及其应用

本文阐述了材料超塑性特征和陶瓷材料超塑性的最近发展，讨论了超塑性在陶瓷成型加工过程中的应用。     

高速钢的组织超细化与超塑性变形力学行为

研究了Ｗ６Ｍｏ５Ｃｒ４Ｖ２高速钢的超细化热处理工艺和超塑变形力学行为。结果表明，该钢在１０４０℃两次循环淬火是实现其超细化的最佳热处理工艺；按此工艺进行预处理后，在８１０℃、初始应变速率为３．３３×１０＾－４ｓ＾－１的最佳变形条件下，该钢的超塑伸长率可达１９２％，流变应力为５８ＭＰａ，应变速率敏感性指数（ｍ）为０．２７。