泡沫铝合金的压缩性能,流通能力及声学性能

研究了泡沫Ａｌ－７Ｓｉ－０．４５Ｍｇ合金的压缩性能、呼能率，压缩后试样在空气中的流通能力，测试闻其吸声和隔声性能，讨论了试样原始孔隙率对上述性能的影响，以及它们之间的相互关系。     

超声微锻造辅助激光熔丝增材制造数值模拟研究

激光熔丝增材制造技术能大大提高制造效率,但制件存在复杂的残余应力,导致制件内部缺陷多.为了解决这些问题,将超声微锻造与滚压相结合对制件表面进行高频率击打,使金属表层产生塑性变形,将原有的拉应力转变成压应力.以TC4为研究对象,利用ANSYS对激光熔丝过程进行热-结构耦合数值模拟,并施加超声滚压微锻造,分析微锻造前后应力场的变化情况.研究结果表明:激光熔丝熔覆层应力分布更加均匀,拉应力减小,甚至转化为压应力,有效地抑制制件内部缺陷的形成.     

新疆大红柳滩地区俘虏沟花岗伟晶岩成矿特征

西昆仑?喀喇昆仑位于特提斯构造域北缘,该地区通过多年的基础地质调查和找矿勘查,已发现多处铁矿、铅锌矿、锰矿矿床。通过详细野外地质调查在新疆喀刺昆仑和田县俘虏沟地区发现一处中型锂铷稀有金属矿床。该矿床属于花岗伟晶岩型,脉体倾向北东30°-50°或西南204°-240°,倾角39°-78°,矿体规模最大者宽约7-8m,北西-南东向延伸1.2Km。Li2O平均品位1.1%~3.3%,Rb2O平均伴生品位为0.04%~0.12%,估算资源量(334)Li2O为8.68万吨,Rb2O为1698.58吨,达到中型锂铷多金属矿床规模。俘虏沟地区中型锂铷多金属矿床的发现,表明在该区域具有形成稀有金属矿产的潜力。     

BESⅢ测量(日)(1530)-→γ(日)-的蒙特卡洛研究

基于BESⅢ合作组的离线软件框架BOSS,利用该合作组产生的1 225 M单举J/Ψ事例,研究在BESⅢ探测器上实现测量到超子辐射稀有衰变过程Ξ(1 530)-→γΞ-的分支比的可能性.以无信号事例的单举J/Ψ事例样本为背景样本,以纯信号蒙特卡罗事例为信号样本,控制信号事例,在分别假设观测到Ξ(1 530)-→γΞ-衰变过程信号显著水平为3σ和5σ的情况下,得到该衰变过程对应的分支比.     

铝合金PLC效应与声发射特性的实验研究

考虑退火温度和应变率对6063铝合金力学性能的影响,采用材料试验机和声发射测试系统对铝合金PLC效应和声发射特性开展实验研究,获得了不同应变率下材料的应力-应变曲线和不同退火温度下声发射参数的变化规律.结果表明,2×10-3,2×10-4,2×10-5s-1应变率加载时,6063铝合金的应力应变曲线表现出明显的PLC现象,降低加载应变率,PLC现象增强,并出现了从A型到C型的转化;加载应变率为2×10-4s-1时,PLC效应的临界应变随退火温度的升高而降低;由于细观结构上可动位错密度的增加,屈服阶段试件中产生的声发射振铃计数急剧增加,达到峰值;进入到塑性强化阶段,声发射活动减弱;弹性变形阶段和塑性强化阶段产生突发型信号,而屈服阶段为连续型信号,与试件的均匀变形以及剪切变形带的形成与传播相关.      

飞秒激光辐照CuZr非晶合金损伤动力学研究

采用考虑了电子压强梯度的双温分子动力学方法,研究了纳米CuZr非晶合金薄膜在脉宽为100 fs,能量密度为0.08～0.16 J/cm~2的飞秒激光辐照下的烧蚀动力学过程.结果表明,低能量密度下,电子压强梯度对靶材的结构损伤过程影响很小.高能量密度下,电子压强梯度对靶材内部的电子温度和晶格温度演化场产生了显著的影响,CuZr非晶合金薄膜的结构存在皮秒量级的由电子压强梯度诱导的非热烧蚀过程,并且随着能流密度的增大,这一超快的非热烧蚀过程在时间尺度上会得到提前.     

钛合金无缝管热连轧工艺及应用

钛合金热熔小,温度下降快,轧制温度控制困难。钛合金材料的高温摩擦和塑性特点使其在热轧过程中容易产生表面缺陷,制约了钛合金无缝管热连轧生产。笔者运用有限元方法模拟了PQF型三辊连轧机将?204mm×16mm的TC4合金坯料轧制成?185mm×7mm的荒管的过程。模拟结果表明:开轧温度900℃,轧制速度2.93m/s条件下,钛合金管的内外温差最高达到250℃,第2和4道次的外表面拉应力超过200MPa,产生缺陷可能性最大。利用模拟结果进行了TC4和TA1现场试制。工业试制结果表明:采用连轧机组可实现钛合金无缝管的高精度轧制,生产的TC4和TA1无缝管的外径偏差0.5%,壁厚偏差10%,与模拟结果相吻合。TA1无缝管屈服强度为237MPa,抗拉强度为321MPa,延伸率为47%,室温CVN冲击功为100J。TC4钛合金无缝管的屈服强度为780～846MPa,抗拉强度为910～960MPa,延伸率为14%～16%,室温CVN冲击功为38～52J。     

In vitro study of human endothelial progenitor cells behaviour on nitrided Ni-free Ti–27Nb alloy

A superelastic Ni-free Ti–27Nb alloy has been synthesized and gas nitrided at high temperature to investigate its suitability for vascular implant applications. The cellular responses of human endothelial progenitor cells (EPCs) to both bare and nitrided Ti–27Nb alloy have been analyzed using Live/Dead staining, MTT assay, fluorescence microscopy and ELISA technique, as well as NiTi alloy for comparison. Live/Dead staining and MTT assay were performed to assess the cellular viability and proliferation, while fluorescence microscopy was used to analyze cell adhesion, cell morphology, and the expression of endothelial cell markers (VE-cadherin and von Willebrand factor). Secretion of the pro-inflammatory chemokine MCP (monocyte chemoattractant protein)-1 by the cells grown in contact with the analyzed materials was further verified using the enzyme-linked immunosorbent assay. The results obtained revealed that adhesion, spreading, viability, proliferation rate and phenotypic markers expression of EPCs were similar on the surfaces of Ti–27Nb and NiTi alloys. Cells exposed to nitrided Ti–27Nb surface exhibited significantly decreased inflammatory response, which may be beneficial for reducing in-stent restenosis incidence.     

Simulation of dynamic recrystallization for an Al-Zn-Mg-Cu alloy using cellular automaton

A cellular automata (CA) model has been developed to predict and control the microstructure evolution during hot deformation on 7085 aluminum alloy. The initial microstructure and thermal-mechanical parameters were used as the input data of the CA model. To link microstructure evolution with macroscopic flow stress, dislocation density was set as an important internal state variable. The hot deformation behavior of 7085 aluminum alloy was studied by isothermal compression tests under a deformation temperature range of 623–723 K and a strain rate range of 0.001-1s^?1 up to true strains of 0.53–1.20. Electron backscattered diffraction technique and the CA model were utilized to systematically investigate the effects of strain, strain rate and deformation temperature on the microstructure evolution, and further to predict the average grain diameter and the recrystallization fraction after deformation. The simulated results were validated by the experimental data to demonstrate the feasibility and predictability of the CA model.     

超重力法制备的LDH涂层对镁合金耐蚀性的提升作用

采用超重力法在旋转填充床（RPB）中制备富马酸根与柠檬酸根复配插层的层状双氢氧化物（LDH）浆液,然后进行水热处理,在AZ31镁合金表面生长出富马酸根与柠檬酸根插层的LDH涂层。利用X射线衍射仪（XRD）、傅里叶变换红外光谱仪（FT-IR）对LDH粉末进行表征,利用X射线光电子能谱仪（XPS）对AZ31镁合金表面的LDH涂层进行表征,结果证明成功制备出富马酸根与柠檬酸根插层的LDH涂层。使用场发射扫描电子显微镜（FESEM）观察LDH涂层的外观形貌,通过电化学试验测试了生长LDH涂层的AZ31镁合金的耐腐蚀性能,结果表明,采用超重力法制备的含有富马酸根与柠檬酸根插层的LDH涂层表面生成完整、致密的覆盖层,几乎看不到簇立状的LDH片。与共沉淀法相比,使用超重力法制备的LDH涂层,其动电位极化曲线拟合出的腐蚀电位更大,腐蚀电流密度更小。在3.5% NaCl溶液中浸泡96 h后,采用超重力法制备的含有富马酸根与柠檬酸根插层的LDH涂层的阻抗值R_ct为56.69kΩ·cm²,大于仅浸泡1 h的采用共沉淀法制备的不含富马酸根与柠檬酸根插层的LDH涂层（R_ct为49.45kΩ·cm²）,表明超重力法制备的LDH涂层表现出更好的耐腐蚀性。