关键词： 镁合金   负差数效应   腐蚀   单价镁离子   理论模型   阳极极化  

摘要： 随着我国工业水平的不断进步,工程应用领域对轻量化的需求愈加迫切,极大推动了镁合金的快速发展。然而,镁合金的耐蚀性较差,严重阻碍了其实际工程应用。为了有效解决镁合金耐蚀性差的问题,亟需深入研究其腐蚀机理。镁合金电化学腐蚀过程中存在典型的负差数效应(Negative difference effect,NDE),即在阳极极化下镁合金的析氢速度随电位升高而增加,与传统的电化学动力学理论相异。近年来,国内外学者对镁合金的负差数效应开展了大量研究,先后建立了局部保护膜模型、单价镁离子模型、溶解脱落模型、氢化镁促溶理论、综合理论、部分电子外电路消耗机理、析氢交换电流密度i0增大机理和电催化机理八种理论模型。基于上述模型,人们深化了对镁合金析氢过程的认识,提升了镁合金腐蚀机理的研究深度。本文综述了镁合金电化学腐蚀过程中负差数效应的基本原理及研究现状,归纳出八种负差数效应的理论模型,总结了各模型的发展历程,指出了它们各自存在的不足之处,展望了镁合金腐蚀负差数效应的研究方向。

关键词： 镁合金   薄壁   车夹具  

摘要： 本文针对某型号尾翼薄壁零件的车削工序加工时,装夹不方便、加工易变形、难保证零件尺寸及形位公差等问题进行了分析,通过设计专用工装夹具,改变装夹方式,优化工艺参数等措施,解决装夹和加工难题,最终制造出的零件满足设计要求,同时提高了生产效率。

关键词： transverse gradient extrusion   multi-type unique textures   mechanical properties  

摘要： Mg-3Al-1Zn(AZ31)sheets were produced by transverse gradient extrusion(TGE)*** flow behavior and dynamic recrystallization during extrusion were systematically *** microstructures,textures,and mechanical behavior of extruded AZ31 sheet were also analyzed and compared with conventional extruded(CE)*** results showed that fine grain structure and multi-type unique textures were formed in TGE sheet because of the generation of extra flow velocity along transverse direction(TD)and flow velocity gradient along extrusion direction(ED)during *** basal poles gradually deviated away normal direction(ND)from edge to center of the TGE sheet along TD,and the largest inclination angle at center region reached around 65°.Furthermore,the basal poles inclined from ED to TD 40°-63°,except for the center region of TGE *** TGE sheet presented higher ductility and strain hardening exponent(n-value),but lower yield strength and Lankford value(r-value)in comparison with the CE *** the basalslip and tensile twins were easy to be activated during deformation,and the largest elongation of 41%and the lowest yield strength of 86.5 MPa were obtained for the ED-center sample in the TGE sheet.

关键词： 复合挤压   镁合金   晶粒细化   织构  

摘要： 针对镁合金室温强度低、塑性差的问题,采用复合挤压工艺在250℃对Mg-4Sn-2Al-1Zn合金进行了挤压,研究了复合挤压对合金的组织演变、织构及力学性能的影响。结果表明,复合挤压能将Mg-4Sn-2Al-1Zn合金的晶粒尺寸由45.2μm细化至3.1μm,组织均匀。挤压后的合金硬度提升,均匀性改善,屈服强度、抗拉强度和断后伸长率分别为204 MPa、287 MPa和21.0%,较匀质态分别提高了140.0%、91.3%和156.1%。动态再结晶是晶粒细化的主要机制,晶粒细化以及挤压后基面织构增强、织构向挤压方向均匀扩展使合金强度、塑性提高,挤压过程中Mg2Sn相破碎进一步提高了合金的力学性能。上述研究表明复合挤压是一种能有效提高镁合金综合性能的工艺。

关键词： 中国铸造协会   项目评价   航天工程   修复技术   江苏省南通市   专家评价   成果评价   刘树生  

摘要： 2023年3月16日,中国铸造协会在江苏省南通市海门区四甲镇通过现场会议形式主持召开了由新江科技(江苏)有限公司、航天工程装备(苏州)有限公司、上海航天精密机械研究所合作完成的“复杂镁合金构件缺陷搅拌摩擦固相修复技术及成套设备研发与应用”项目评价会议,该项目顺利通过成果评价。会议邀请了高校、科研院所和企业等7位国内知名专家组成专家评价委员会,中国铸造协会行业发展部刘树生主持了会议。

关键词： 扩建项目   国防军工   航空航天   轻质材料   欧几里得   挤压材   媒体报道   碳中和  

摘要： 据国外媒体报道,美国PMT集团子公司特维斯公司(Terves)正在扩建俄亥俄州欧几里得(Euclid)镁材挤压厂,以扩大可溶性挤压材的生产能力,扩建项目:一条立式半连续镁合金圆锭铸造线,这是新世纪北美建的首条圆锭铸造线,一个30000平方英尺的厂房。通过扩建,特维斯公司将进入轻量化产品市场,向汽车、航空航天、国防军工等和其它关心碳中和的公司提供镁合金材料和铸件。镁是最轻的结构材料,是可持续的轻质材料,助力循环经济的发展,这都是当今制造企业面临的主要课题之一。

关键词： 锻造温度   Mg-7Al-3Sn镁合金   耐腐蚀性能  

摘要： 为了研究锻造温度对汽车用镁合金组织及性能的影响，本文在锻造过程中砧座预热温度、锻造变形量等不变条件下，测试了不同始锻温度和终锻温度下Mg-7Al-3Sn镁合金试样的显微组织、耐腐蚀性能和力学性能。结果表明：在420℃始锻、300℃终锻的试样平均晶粒尺寸最大，耐腐蚀性能和力学性能最差；在470℃始锻、340℃终锻的试样平均晶粒尺寸最小，耐腐蚀性能和力学性能最佳。与420℃始锻、300℃终锻试样相比，470℃始锻、340℃终锻时试样的平均晶粒尺寸减小64.1%，腐蚀电位正移12.5%，抗拉强度提高23.7%，屈服强度提高23.1%。Mg-7Al-3Sn镁合金在470℃始锻、340℃终锻时具有良好的耐腐蚀性能和力学性能。

摘要： Magnesium-based medical implants have the potential to overcome several complications that arise with permanent metallic implants. Magnesium-based implants are biodegradable such that they can undergo absorption once their load-bearing function has been completed, thereby avoiding a secondary removal surgery. However, several challenges must be overcome as non-uniform and highly localised pitting corrosion mechanisms can lead to early failure of implants. Despite this, the majority of experimental studies to date tend to consider bulk measures of corrosion by measuring mass loss, while the role of localised surface corrosion mechanisms have been largely ignored, or evaluated using qualitative approaches. As a con sequence, there is limited quantitative understanding on how pit formation (e. g. severity and spatial distribution) affects the overall mechanical performance of magnesium-based al loys. The objective of this thesis is to investigate the relationship between spatial corrosion performance with the corresponding mechanical integrity of a magnesium WE43 alloy for orthopaedic implants by means of an experimental and numerical approach. In this thesis, a three-dimensional automated detection framework, 'PitScan' was developed to systematically evaluate the extent and morphology of surface-based pitting corrosion of cylindrical magnesium specimens undergoing corrosion through in-vitro immersion. PitScan used a Python-based approach to analyse micro-computed tomography images (µCT) of cylindrical specimens undergoing corrosion. It was used to establish relationships between local pitting parameters and mechanical performance, which was determined through uniax ial mechanical testing. Additionally, a finite element surface-based degradation model was implemented to further explore the correlation between the severity of localised corrosion mechanisms and mechanical integrity. These experimental and computational approaches were then used to investigate the influen

关键词： 丝素蛋白   透明质酸   巯基-烯点击化学   光固化   水凝胶   生物相容性  

摘要： 目的:以丝素蛋白和透明质酸为原料设计并制备医用天然聚合物水凝胶.方法:对丝素蛋白和透明质酸进行巯基化及双键化改性,在紫外光条件下,利用巯基-烯点击聚合快速固化成胶.通过氢-1核磁共振波谱法表征改性丝素蛋白及透明质酸的接枝率;流变学测试表征水凝胶的凝胶点;扫描电镜观察水凝胶的内部微观结构;压缩测试表征力学性能;质量法测定溶胀率及降解率;将水凝胶与细胞共培养,通过乳酸脱氢酶法测定细胞毒性,漂浮计数法测定细胞黏附性并用扫描电镜及荧光显微镜观察凝胶表面的细胞生长与分化状况.结果:改性后的丝素蛋白和透明质酸的官能团取代度分别为17.99%和48.03%.制备所得的丝素蛋白/透明质酸复合水凝胶的凝胶点为40～60 s,凝胶内部具有孔状结构,压缩强度达450 kPa且循环十次不破裂.复合水凝胶可吸收自身质量4倍甚至10倍的水.水凝胶可生物降解,35 d后的降解率达28%～42%.复合水凝胶的细胞毒性较弱,细胞黏附性较好,细胞在凝胶表面生长和分化状况良好.结论:光固化丝素蛋白/透明质酸复合水凝胶能快速成胶、力学性能优异、生物相容性好,具有可调的溶胀率及降解度,在生物医学上具有一定的应用潜力.

标准号: T/CI 062-2023