基于数值模拟的挤压参数对AZ91镁合金管转角焊合室分流挤压焊合压力的影响规律研究

提出了一种镁合金管材转角焊合室分流挤压新工艺，该工艺可在有效延长焊合室长度和焊合时间前提下保证舌针刚度，从而保证管材尺寸精度，并且可通过转角剪切变形机制增加预焊合金属变形量和动态再结晶程度，从而有利于提高管材性能和焊缝焊合性能。利用有限元法揭示了转角焊合室分流挤压成形过程中金属的流动特征，应变分布特征和焊合室内的静水压力分布特征。结果表明，整个挤压过程无金属折叠，从而保证管材的表面质量；流经转角后预焊合金属变形量明显增加，有利于提高管材质量和焊缝质量。最后，研究揭示了坯料初始温度，挤压速度和模具转角对焊合室内静水压力的影响规律。结果表明，随着挤压速度的增加和模具转角的增大，转角焊合室内静水压力增大；随着坯料预热温度的增加，转角焊合室内静水压力呈先增大后减小的趋势。     

Fabrication and properties of the superhydrophobic ceria-based composite coating on magnesium alloy

A superhydrophobic ceria-based composite coating is developed to improve anticorrosion properties of AZ61 magnesium alloy, fabricating via chemical conversion method followed by hydrothermal treatment. The cerium conversion coating has a block structure with microcracks. After the hydrothermal treatment, a dense CeO₂ layer, porous CeO₂ nanorods, and stearic absorbing layers are grown stepwise on the conversion coating. And the composite coating is hydrophobic or even superhydrophobic and has almost no microcracks. As the hydrothermal reaction time increases, the water contact angle of the composite coating first increases and then decreases, and it reaches the maximum value of 152° after hydrothermal treatment for 4 h. Both the dense CeO₂ layer and the superhydrophobic stearic absorbing layer can effectively prevent the electrolyte from contacting the substrate; the corrosion current density of the superhydrophobic composite coating is lower than that of the hydrophilic composite coating and the cerium conversion coating, and has the best corrosion resistance.     

水氯镁石制备金属镁的过程集成与能量分析

以无水氯化镁和氧化镁作为中间产物，电解和热还原为两个关键方法，集成各种相关过程，构建了从水氯镁石到金属镁的综合过程网络，其中涉及24个物种、20个化学过程和25个工艺路线；建立了最低能耗分析模型用于简单和复合过程的能量分析；利用物质的标准生成焓和多温等压摩尔热容，计算得出全部反应过程及工艺过程的能量消耗和热量移除。结果表明基于还原法的最优路径是水氯镁石用石灰法转为氢氧化镁，进而煅烧成氧化镁，再铝热还原成金属镁，该过程能耗360.15 kJ/mol，放出热量–315.46 kJ/mol；基于电解法的最优路径是石灰乳法生成氢氧化镁，再煅烧成氧化镁，通过在熔融电解质中电解生成金属镁，该过程能耗738.54 kJ/mol，放出热量–135.42 kJ/mol。无水氯化镁制备耗能高，不在最优路径中。     

镁合金网格壁板压弯成形数值模拟及实验研究

为探索镁合金整体壁板压弯成形的可行性,以及镁合金壁板压弯成形过程中金属的流动规律,对AZ31镁合金网格壁板压弯成形进行了数值模拟和实验研究。建立了有限元数值模拟的几何模型,采用有限元计算软件对AZ31镁合金网格壁板压弯成形过程进行了数值模拟研究,分析了镁合金网格壁板压弯成形中的温度场、应变场、应力场、破坏系数等的分布规律。确定了合适的AZ31镁合金壁板压弯成形工艺参数,并对镁合金网格壁板压弯成形进行了实验研究,获得了合格的镁合金网格壁板弯曲件,并分析了镁合金网格壁板成形件尺寸精度,模拟结果与实验结果相吻合,最大相对误差为16.7%。     

FCC废催化剂镁改性催化裂化性能再生研究

提出并证实了高的强酸性位可接近性导致FCC废催化剂失活的机制。基于所提出的失活机制，采用浸渍法对FCC废催化剂进行镁改性再生。对所制备的再生FCC废催化剂进行了表征并考察了其重油催化裂化性能。表征结果表明，与未改性的FCC废催化剂相比，再生FCC废催化剂表面酸强度被一定程度地削弱，而表面总酸量和结构性质参数未出现显著改变。重油催化裂化结果表明，得益于适宜的表面酸性，再生FCC废催化剂的催化裂化反应性能得到极大改善。与未改性的FCC废催化剂相比，再生FCC废催化剂的汽油产率显著增加了3.04个百分点，同时干气、液化气、焦炭和重油产率则分别下降了0.36、0.81、1.28和0.87个百分点，这使得所制备的再生FCC废催化剂可以代替部分新鲜FCC催化剂使用。最后，探讨了再生FCC废催化剂表面酸性改变机理。     

ZK60镁合金表面滚压强化试验研究

试验研究了ZK60镁合金表面滚压加工中工艺参数对试件表面粗糙度、表面形貌、表面残余应力和表层显微硬度的影响,结果表明滚压力和重复滚压次数对试件的表面粗糙度、表面形貌以及表面残余应力和表层硬度影响程度较大,滚压速度影响较小。对精车ZK60镁合金试件进行滚压加工,试件表面粗糙度R a、R z最大减小了50.3%和48.1%;残余压应力最大可达-54.55 MPa;显微硬度从试件表层到内部基体材料逐渐降低,表层硬度值最大为92.83 HV 0.25,比基体材料硬度提高了15.32%。     

不同方法发酵的酸豆角品质对比分析

本文将研究不同方法发酵的酸豆角品质对比分析。选取质地嫩脆、条形均匀、无病虫害的新鲜豆角为泡制原料。采用自然干法发酵、自然湿法发酵与纯种湿法发酵的发酵方法制作酸豆角。检测发酵过程中，pH值、还原糖含量、总酸含量、总糖含量、亚硝酸盐含量以及氨基酸态氮含量，分析纯种湿法发酵与自然湿法发酵对酸豆角品质的影响。结果表明：纯种湿法发酵25 d后，其pH值和还原糖含量分别为3.92、0.03%，均高于自然湿法发酵；总酸、总糖、亚硝酸盐含量、氨基酸态氮含量分别为0.25%、0.04%、0.01 mg/kg和0.01%，均低于自然湿法发酵。另外，纯种湿法发酵酸豆角的甲氧基乙酸含量为0.37%，乙酸乙酯为0.51%，含水量为81.15%，感官评分为45.52，均高于自然干法发酵。纯种湿法发酵对酸豆角品质的效果最好，亚硝酸盐的含量在发酵后期显著降低，感官评分较高，对豆角工业化生产提供了较好的参考价值。     

Preparation of microencapsulated carbon microspheres coated by magnesium hydroxide/polyethylene terephthalate flame–retardant functional fibers and its flame retardant properties

In order to improve the compatibility between the flame retardants of carbon microspheres coated by magnesium hydroxide (MH@CMSs) and the PET matrix and improve the spinnability of the masterbatch, MH@CMSs have been microencapsulated by PET to obtain microencapsulated carbon microspheres coated by magnesium hydroxide flame retardants – MMH@CMSs.Morphologies and structures of MMH@CMSs have been studied by scanning electron microscope (SEM), transmission electron microscopy (TEM), and FTIR, which showed that an organic shell layer of PET as capsule wall was coated on the surface of MH@CMSs. A series of MMH@CMSs/PET fibers with different MMH@CMSs contents were successfully prepared through the melt-spinning method. The morphology and structure of MMH@CMSs/PET fibers were characterized by SEM and FTIR. The flame retardancy of MMH@CMSs/PET fibers was determined via limiting oxygen index (LOI) test and cone calorimeter. Results showed that the MMH@CMSs/PET fibers possessed optimum flame retardancy when the MMH@CMSs content is 0.6 wt.%, at which the LOI reached a maximum of 25.8, and the pk-HRR, total heat release, and total smoke release were reduced by 27.4, 20, and 13.6%, compared with pure PET fibers, respectively. Moreover, the flame-retardant mechanism was studied by thermogravimetric analysis, thermogravimetric analysis-infrared spectrometry, and the SEM of the residue char, which disclosed that MMH@CMSs enhanced the thermal stability of PET fibers, and promoted PET fibers to form a dense and continuous protective char layer that effectively blocked heat transfer and combustible gas release.     

热处理对挤压态Mg-6Gd-5Y-1Zn合金组织与性能的影响

通过对Mg-6Gd-5Y-1Zn(质量分数,%)合金在固溶和时效处理状态下显微组织和力学性能的研究发现,α-Mg基体、沿挤压方向分布的条状18R-LPSO相、少量的Mg₂₄(GdYZn)₅ 相以及细层片状的14H-LPSO相构成了挤压态合金的组成相。挤压态合金经固溶(T4)处理后,一部分18R-LPSO相溶入基体,并且基体中的14H-LPSO相伸长同时粗化。挤压态合金经过固溶加时效(T6)处理后,大量β′相从α-Mg基体中析出。T6态合金的室温力学性能最好,其屈服强度、抗拉强度及伸长率分别为272 MPa、406 MPa和6.1%。β′相沉淀也发生在挤压态合金的直接人工时效(T5)处理过程,但相比于T6处理,14H-LPSO相和β′相在基体中的体积分数均偏低。