Al-4Cu-1.3Mg-0.9Si合金的析出强化行为

通过硬度测试、差示扫描量热法(DSC)分析、拉伸性能测试和透射电镜(TEM)微观组织观察,研究了Al-4Cu-1.3Mg-0.9Si合金的析出强化行为。结果表明:合金具有较强的析出强化能力;合金在160～220℃下时效,随时效温度的升高,合金的时效响应速率加快,时效峰值硬度有所下降;合金在190℃时效态时,其主要析出相为S相,在190℃/24h时效态合金中还发现少量的方块状相;合金经190℃/24h时效后其常温和高温抗拉强度较同等条件下制备、同等热处理状态下的Al-4Cu-1.3Mg合金有明显的提高。     

固溶制度对7050铝合金微观组织和腐蚀性能的影响

采用光学显微镜(OA)、扫描电镜(SEM)、透射电镜(TEM)等手段和电化学、浸蚀、慢应变速率拉伸(SSRT)等测试方法,研究不同固溶热处理制度对7050铝合金板材微观组织和腐蚀性能的影响。结果表明:单级固溶将η(MgZn2)相完全溶入Al基体中,而S(Al2CuMg)相仍然大量存在,固溶度低,时效后晶内析出密度低;双级固溶使S相部分溶解,合金晶粒长大,再结晶分数高;逐级固溶使η和S相完全溶解,合金充分回复,时效后晶内析出密度高,再结晶分数低;不同固溶+T6时效态合金的抗应力腐蚀性能从大到小依次为逐级固溶>双级固溶>单级固溶。     

典型焊接参数对铝锂合金FSW对接接头疲劳性能的影响

采用疲劳试验机对3种不同对接工艺的Al-Li-S4铝锂合金FSW对接接头及母材进行了疲劳性能测试,并采用光学显微镜和扫描电镜对组织和断口进行了分析。结果表明:在210MPa应力水平下,Al-Li-S4-T8铝锂合金母材在疲劳寿命达到200万次;在600/400、800/80、800/2003种典型FSW工艺条件下,800/200参数接头疲劳性能最优,在170MPa应力水平下,接头疲劳寿命可达200万次;Al-Li-S4合金FSW接头疲劳断裂大部分从焊缝表面起裂,这可能与FSW过程中金属材料的周期性流动和周期性微观组织使焊缝内部出现强度薄弱区或应力集中有关。     

Li含量对Mg-6Y-3Zn-xLi合金微观组织和力学性能的影响

采用氩气保护真空熔炼的方法制备了铸态Mg-6Y-3Zn-xLi（x=0,5,8,11,wt%）合金,并对其进行了均匀化处理和热挤压变形。通过OM、SEM以及拉伸试验等手段研究了Li含量对合金微观组织与力学性能的影响。结果表明：随着Li含量的增加,铸态Mg-6Y-3Zn-xLi合金基体由α单相结构逐渐转变为（α+β）双相结构,晶粒尺寸和共晶化合物的形貌及分布规律也发生明显变化。均匀化处理后Mg-6Y-3Zn-xLi合金中形成的块状长周期有序（LPSO）结构相,随Li含量的增加其体积分数逐渐降低,（Mg,Zn）₂₄Y₅相数量则逐渐增多。Mg-6Y-3Zn-8Li合金进过均匀化处理和热挤压变形后表现出最优的综合力学性能,抗拉强度和延伸率分别达到278 MPa和11.6%,这主要是由于均匀分布的被破碎细化的块状LPSO相和大量细小动态再结晶的共同强化作用。     

单轴拉伸下HTPB推进剂细观损伤演化实验研究

为了研究HTPB固体推进剂在单轴拉伸载荷下的细观损伤机理,采用高精度微CT对拉伸过程中的HTPB推进剂进行了扫描实验,获取了不同拉伸应变下推进剂的细观损伤形貌以及孔隙率变化规律,分析了推进剂细观损伤对宏观力学性能的影响。结果表明：初始损伤的存在使得推进剂在受到载荷作用时AP颗粒就开始脱湿,AP颗粒脱湿形成的孔洞是推进剂细观损伤的主要形式。拉伸应变较小时,相对小尺寸AP颗粒而言,大尺寸AP颗粒附近的缺陷更容易发展成孔洞。随着拉伸应变的增大,绝大多数AP颗粒都开始脱湿,在推进剂宏观断裂前,大量AP颗粒脱湿形成的孔洞发生汇合,最终使推进剂断裂。加载过程中推进剂孔隙率随拉伸应变呈指数变化,初始孔隙率为1.8%,60%拉伸应变时孔隙率为19.1%。推进剂宏观力学性能处于线弹性段时,其内部细观损伤依旧在不断增加,当细观损伤累积到一定程度时推进剂的承载能力下降,宏观力学性能进入非线性段;由于AP颗粒仍具有一定的增强作用,且HTPB基体也具备承载能力,所以推进剂的应力随拉伸应变呈缓慢增加的趋势。     

Microstructure and Mechanical Properties of Cross-rolled Ti50Ni47Fe3 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.     

氰酸酯/线性酚醛/环氧树脂三元体系的研究

 在氰酸酯树脂/ 环氧树脂体系中引入了线性酚醛树脂,得到氰酸酯树脂/ 环氧树脂/ 线性酚醛树脂三元共聚体系。采用差示扫描量热法(DSC) 研究了三元共聚体系的反应动力学,根据Kissinger 方程和Ozawa 方程得到体系的表观活化能( Ea) :62. 94kJ / mol,确定了体系的反应速率常数K。比较了纯氰酸酯树脂、氰酸酯/ 环氧树脂体系和三元树脂体系玻璃布层压板的力学性能、介电性能以及吸湿率。结果表明,线性酚醛树脂用量为15wt %的三元体系复合材料的弯曲强度和层间剪切强度分别比氰酸酯/ 环氧树脂体系复合材料提高了6 %和15 %,介电损耗和吸水率分别降低了33 %和8 %。     

Optimal assimilation for ionospheric weather – Theoretical aspect

Observation, specification and prediction of ionospheric weather are the key scientific pursuits of space physicists, which largely based on an optimal assimilation system. The optimal assimilation system, or commonly called data assimilation system, consists of dynamic process, observation system and optimal estimation procedure. We attempt to give a complete framework in this paper under which the data assimilation procedure carries through. We discuss some crucial issues of data assimilation as follows: modeling a dynamic system for ionospheric weather; state estimation for static or steady system in sense of optimization and likelihood; state and its uncertainty estimation for dynamic process. Meanwhile we also discuss briefly the observability of an observation system; system parameter identification. Some data assimilation procedures existed at present are reviewed in the framework of this paper. As an example, a second order dynamic system is discussed in more detail to illustrate the specific optimal assimilation procedure, ranging from modeling the system, state and its uncertainty calculation, to the quantitatively integration of dynamic law, measurement to significantly reduce the estimation error. The analysis shows that the optimal assimilation model, with mathematical core of optimal estimation, differs from the theoretical, empirical and semi-empirical models in assimilating measured data, being constrained by physical law and being optimized respectively. The data assimilation technique, due to its optimization and integration feature, could obtain better accurate results than those obtained by dynamic process, measurement or their statistical analysis alone. The model based on optimal assimilation meets well with the criterion of the model or algorithm assessment by ‘space weather metrics’. More attention for optimal assimilation procedure creation should be paid to transition matrix finding, which is usually not easy for practical space weather system. High performance computing hardware and software studies should be promoted further so as to meet the requirement of large storage and extensive computation in the optimal estimation. The discussion in this paper is appropriate for the static or steady state or transition process of dynamic system. Many phenomena in space environment are unstable and chaos. So space environment study should include and integrate these two branches of learning. This revised version was published online in August 2006 with corrections to the Cover Date.     

酚醛树脂杂化磷酸盐基复合材料的研究

用酚醛树脂对磷酸盐进行了杂化，并用杂化基体制备了玻璃纤维增强的复合材料。考察了酚醛树脂加入量对复合材料的力学性能、吸水性和介电性能的影响。结果表明，酚醛树脂加入后。磷酸盐复合材料的力学性能明显提高，弯曲强度从50MPa提高到100MPa以上；吸水性显著下降，吸湿率从5．5％降低到1．5％左右；同时复合材料的介电性能亦有改善。     

三维编织复合材料蠕变行为的试验研究

对不同编织结构、不同编织角、不同纤维体积含量和不同应力水平下的三维编织复合材料试件进行了蠕变测试实验,研究了三维编织复合材料的蠕变性能.结果表明,三维四向编织复合材料的蠕变性能低于五向编织复合材料;编织角小的材料抗蠕变性能较好;纤维体积含量高的材料抗蠕变性能较好.并且材料所受应力水平越高,蠕变速率越高.此外,还表明幂指函数可以较好地拟合三维编织复合材料的蠕变曲线.