冲孔落料折弯复合模设计

介绍了在冲孔落料后用可滑动折弯凹模与可滑动折弯凸模相结合对薄片形件进行弯边，模具结构简单、巧妙，对同类产品具有一定的借鉴作用。     

反对称矩阵的外在美和内在美的教学呈示

关于对称矩阵的美韵,笔者已经撰文做过研究,而反对称矩阵的美韵并不亚于对称矩阵。本文对反对称矩阵之美亦从“内”与“外”进行分析和探索。     

粉末冶金法制备SiC晶须增强MB15镁基复合材料

采用粉末冶金法制备了SiC晶须增强镁基复合材料(SiCW／MB15)试样。通过检测基体显微硬度探讨了SiCW对镁合金时效规律的影响，并借助扫描电镜(SEM)、透射电镜(TEM)和拉伸试验，研究了混粉方式对复合材料室温力学性能、SiCW分布及显微结构的影响。结果表明，MB15及其复合材料的时效硬化曲线上均存在双峰现象；SiCW的加入既提高了MB5的硬度，又加快了其时效速度：混粉方式对晶须分布及SiCW／MB15复合材料的室温力学性能影响很大。     

SiO2凝胶体系中M型锶铁氧体的制备及其磁性能

利用溶胶-凝胶法在SiO2凝胶体系中制备了纳米级的锶铁氧体磁性微粒，该磁性微粒组成为3O％SrFe12O19和70％SiO2(质量百分含量)。对该微粒进行了XRD分析，利用VSM对样品进行了磁性能研究。研究表明，相对于共沉淀法制备的纯锶铁氧体微粒，在SiO2凝胶体系中制备的SrM微粒仍保持为六方磁铅石型结构，但是粒径明显降低，850℃结样品的粒径约为31nm；且内禀矫顽力Hc有了显著的提高，850℃烧结样品的内禀矫顽力达到518．4kA／m，而比饱和磁化强度则有所下降。并对其磁性能变化的原因进行了分析。     

Design of Bulk metallic glasses with high glass forming ability and enhancement of plasticity in metallic glass matrix composites: A review

To overcome some of the limits of existing metallic alloys, a new alloy design concept has been introduced recently in order to control the crystallinity, i.e. to utilize crystalline, quasicrystalline, and amorphous structures. In particular, bulk metallic glasses (BMGs) receive great attention because of their unique properties due to their different atomic configuration. Recently, significant progress in enhancing glass forming ability (GFA) has led to the fabrication of BMGs having potential for application as structural and functional materials. Moreover, successful design of BMG matrix composite microstructure suggests that the plasticity of BMGs can be controlled properly. In this review article, we introduce recent research results on the design of BMGs with high GFA and on the enhancement of plasticity in metallic glass matrix composites.     

脱氢表雄酮对大鼠骨关节炎影响的实验研究

目的:;研究脱氢表雄酮(DHEA)对大鼠实验性骨关节炎(OA)的影响。方法: 40 只大鼠随机分4组:正常对照组、模型对照组、DHEA 大、小剂量组。除正常对照组外,其余3组右膝木瓜蛋白酶关节腔注射法建立OA 模型。然后DHEA 大、小剂量组两组右膝分别关节腔注射50 μmol· L^-1 和100μmol·L^-1 的DHEA 溶液150 μl,正常对照组、模型对照组两组右膝均注入生理盐水150 μl,每周2 次,注射5周。6周后处死大鼠,大体形态学、组织学、生化及免疫组化的方法评价关节软骨情况。结果: 手术显微镜下观察,见DHEA 大、小剂量组两组软骨损害均较模型对照组明显减轻。DHEA 大、小剂量组Mankin's评分、关节腔冲洗液一氧化氮含量、滑膜丙二醛含量及关节软骨基质金属蛋白酶,1和9的表达均较模型对照、组显著降低, DHEA 大剂量组上述指标均较DHEA 小剂量组显著降低。且两组关节腔冲洗液和血清超氧化物歧化酶活性均较模型对照组显著升高, DHEA 大剂量组上述指标升高均较DHEA小剂量组更明显。结论: DHEA 对OA 软骨有保护作用,且存在剂量依赖性,保护机制可能是抑制关节软骨基质金属蛋白酶表达、减少一氧化氮释放和增强抗氧化作用。     

颗粒激发形核在热挤压Al6061/SiCp复合材料再结晶过程中的作用

采用电子背散射衍射技术,研究SiCp增强热挤压A16061铝合金复合材料的织构和微观组织演变.A16061铝合金及其Ni包覆SiCp增强的复合材料织构中都存在强的β纤维,其轴平行于挤压方向.在未用SiCp增强的热挤压A16061铝合金中,除了主要的立方织构001)<100>,在完全再结晶晶粒中也存在部分等轴结构.这种再结晶织构的出现归因于粒径小于5μm的SiCp粒子的形成而产生的粒子激发形核.在这些条件下,低Z(～1012 S-1)值证实了粒子激发形核是再结晶的主导机制之一,且受变形区的形成而非储能的控制.     

Effect of Cu addition on microstructural evolution and hardening of mechanically alloyed Al−Ti−O in-situ composite

The microstructure formation and strengthening of an Al−5wt.%TiO₂ composites with additions of 5 wt.% Cu and 2 wt.% stearic acid (as a process control agent, PCA) during mechanical alloying and subsequent thermal exposure were studied. The powder composites were prepared by high-energy ball milling for up to 10 h. Single line tracks of the powders were laser melted. Optical and scanning electron microscopy, XRD analysis and differential scanning calorimetry were used to study microstructural evolution. The results showed that the Cu addition promotes an effective mechanical alloying of aluminum with TiO₂ from the start of milling, resulting in higher microhardness (up to HV 290), while the PCA, on the contrary, postpones this process. In both cases, the composite granules with uniform distribution of TiO₂ particles were formed. Subsequent heating of mechanically alloyed materials causes the activation of an exothermic reaction of TiO₂ reduction with aluminum, the start temperature of which, in the case of Cu addition, shifts to lower values, that is, the transformation begins in the solid state. Besides, the Cu-added material after laser melting demonstrates a more dispersed and uniform structure which positively affects its microhardness.     

纳米Al2O3增强颗粒对热锻AZ31B镁合金单轴及高周疲劳性能的影响(英文)

研究热锻工艺对AZ31B合金和AZ31B/1.5vol.%Al₂O₃纳米复合材料在静态和循环加载下的显微组织和力学性能的影响。首先将铸态合金和复合材料在450°C下进行均匀化热处理,然后在450°C下进行开式模锻。结果表明,增强颗粒的存在有利于晶粒细化和改善动态再结晶。锻造工艺能更有效地消除铸态合金工件中的孔隙。与铸态和锻态合金试样相比,锻态复合材料的显微硬度分别提高80%和16%。与锻态合金的相似区域相比,锻态复合材料的极限抗拉强度和最大拉伸应变分别提高45%和23%,极限压缩强度和最大压缩强度分别提高50%和37%。复合材料在低应变区的疲劳寿命提高,而在高应变区的疲劳寿命降低。与AZ31B试样不同,复合材料的拉伸、压缩和高周疲劳行为对施加应变的敏感性较低,这与试样在热锻前后的孔隙率有关。