2024铝合金中沉淀相对PLC效应的影响

对2024铝合金进行不同温度下的热处理, 得到了一系列具有不同溶质原子浓度的基体及析出相含量的铝合金试样. 将这些试样分别在低温(-100 ℃)和室温(25 ℃)下进行拉伸实验, 分析其锯齿幅值和临界应变随应变率的变化趋势. 结果表明, 溶质原子是 Portevin--Le Chatelier (PLC)效应的必要因素, 单纯的位错切割沉淀相不足以产生PLC效应, 只能影响PLC效应, 并且沉淀相对PLC效应的影响在中等拉伸应变率时表现明显.     

析出相对AZ91D挤压镁合金PLC效应的影响

研究了具有不同析出相含量的AZ91D挤压镁合金在拉伸变形中出现的Portevin-Le Chatelier(PLC)现象,讨论了析出相对其产生PLC效应的影响规律,指出AZ91D挤压镁合金产生PLC效应的微观机理。结果表明:Al溶质原子的浓度是影响AZ91D挤压镁合金产生PLC效应的主要因素,β-Mg_(17)Al_(12)相的析出抑制了AZ91D挤压镁合金不稳定塑性行为。当β-Mg_(17)Al_(12)相析出量较高时,AZ91D挤压镁合金表现为稳定的塑性流变过程,其对应的应力-应变曲线为光滑的曲线;随着β-Mg_(17)Al_(12)相析出量的降低,固溶于Mg基体中的Al原子量增加,固溶体内溶质原子浓度提高,拉伸曲线表现出明显的锯齿屈服并逐渐剧烈,即AZ91D挤压镁合金的PLC效应随β-Mg_(17)Al_(12)相析出量的减少和Al溶质原子浓度的提高而增强;当β-Mg_(17)Al_(12)相含量为1.0mass%,对应的曲线上只出现一个锯齿抖动,这是AZ91D挤压镁合金产生PLC效应的临界状态。     

Mg-9Gd-4Y-0.6Zr析出相在高温拉伸中的相变

通过透射电镜观察Mg-9Gd-4Y-0．6Zr合金挤压T5态在300℃和350℃的高温短时拉伸过程中析出相的变化情况。结果表明，合金在350℃拉伸过程中（拉伸持续时间约1h）析出相没有发生转变，仍为β′相。合金在300℃和350℃拉伸时β′相从拉伸前的网状分布逐渐转变为平行于变形方向的条状分布，降低了对变形的阻力；部分溶质原子回溶造成析出相的体积分数下降；合金在300℃时拉伸过程中没有发生交滑移，而在350℃时拉伸过程中则发生交滑移现象；这些都导致合金强度和耐热性的下降。     

固溶时效工艺对ZA27合金组织和性能的影响

采用扫描电镜(SEM)、X射线衍射(XRD)和力学性能测试等手段研究了固溶处理对ZA27合金组织和性能的影响。在300～380℃范围,合金经不同温度固溶处理1 h,水淬后进行相同的时效(160℃×8 h)处理。分析了在不同温度固溶处理的淬火态和时效态合金的显微组织及力学性能。结果表明,在365℃固溶处理能够使溶质原子充分溶入基体,时效析出相数量多、尺寸小、分布均匀,时效强化效果最好。ZA27合金的优选固溶工艺为365℃×1 h。     

Ce含量对Mg-Li-Al-Zn合金显微组织和拉伸性能的影响(英文)

制备了Mg-5Li-3Al-2Zn-xCe(x=0-2.5;质量分数,%)铸态合金,并将所得合金分别于300°C和370°C进行均匀化和固溶处理;研究固溶处理后合金显微组织和拉伸性能的变化。结果表明,合金中加入Ce后出现Al2Ce/Al3Ce析出相,此时合金主要由α-Mg、Al2Ce、Al3Ce和AlLi相组成;固溶处理后合金中AlLi和Al-Ce析出相数量减少。析出相的数量与形态对合金的力学性能十分重要,含有1.0%Ce的合金获得了优良的拉伸性能。固溶处理后Mg-5Li-3Al-2Zn-0.5Ce合金的强度和伸长率都得到了大幅度的提高,这是因为合金在固溶处理后由于基体中的溶质原子增加而获得良好的固溶强化作用。     

固溶时效对挤压态LAZ941-0.5Y合金组织和力学性能的影响北大核心CSCD

通过OM、XRD、DSC、SEM和力学性能测试等手段,研究了挤压态LAZ941-0.5Y合金经不同的固溶时效处理后的组织和力学性能。结果表明:挤压态合金经固溶处理后,MgLi_2Al和AlLi相完全溶入基体,产生显著的固溶强化效果;50℃时效初期,溶质原子扩散缓慢导致析出动力不足,过饱和基体中析出短棒状的MgLi_2A过渡相,随时效时间延长,MgLi_2A相发生形貌转变,由短棒状变成点状;随时效温度的升高,溶质原子扩散速率加快,MgLi_2A相析出速率变快,部分MgLi_2A亚稳相分解为AlLi相,同时有AlLi从基体中析出。合金的峰值时效在50℃时效0.5 h时发生,随温度的升高很快发生过时效,其主要原因是AlLi软化相的出现。     

6063铝合金的TTP曲线与淬火敏感性

采用中断淬火技术测定了6063铝合金的时间-温度-性能(TTP)曲线,透射电镜研究了6063铝合金的淬火敏感性.结果表明,6063铝合金的淬火敏感性低于6061和6082铝合金的,合金的鼻尖温度为360℃,淬火敏感区间为300～410℃.微观组织观察表明,在敏感区间内,β-Mg2Si平衡相优先在(AlxFeySiz)相上非均匀形核而析出,且在360℃鼻尖温度时的长大速度最快.平衡相的析出导致合金溶质原子的浓度下降,减少了时效时的β"强化相的数量,降低了强化效果.因此,对于6063铝合金大型材的淬火,一方面,在淬火敏感区间(410～300℃)应加大冷却速率以抑制平衡相的析出,从而获得较佳的时效强化效果;另一方面,适当减小从固溶温度到410℃以及低于300℃时的冷却速率,从而减小淬火应力.     

固溶温度对6061铝合金组织和性能的影响

采用光学显微镜(OM)、扫描电镜(SEM)和X射线衍射(XRD)等分析手段,研究固溶温度对6061铝合金热挤压板材的显微组织、力学性能及拉伸断口形貌的影响.结果表明,实验合金的强度和硬度随着固溶温度的升高而提高,当基体有轻微过烧时强度并没有降低;实验合金的最佳固溶工艺为565℃×40 min.XRD物相分析表明,在固溶处理过程中发生溶解的析出相粒子主要为Mg2Si,而残留的粗大析出相则主要是富Fe化合物.通过基体点阵常数的精确测量可以很好的表征合金的固溶程度.固溶处理后残留的析出相粒子是影响合金拉伸断口形貌的主要因素.当固溶温度低于535℃时,合金的断裂属于单一的韧窝断裂;当固溶温度高于535℃时,合金的断裂是由沿晶脆性断裂和韧窝断裂组成的混合断裂.     

固溶时效对挤压态LAZ941-0.5Y合金组织和力学性能的影响

通过OM、XRD、DSC、SEM和力学性能测试等手段,研究了挤压态LAZ941-0.5Y合金经不同的固溶时效处理后的组织和力学性能。结果表明:挤压态合金经固溶处理后,MgLi_2Al和AlLi相完全溶入基体,产生显著的固溶强化效果;50℃时效初期,溶质原子扩散缓慢导致析出动力不足,过饱和基体中析出短棒状的MgLi_2A过渡相,随时效时间延长,MgLi_2A相发生形貌转变,由短棒状变成点状;随时效温度的升高,溶质原子扩散速率加快,MgLi_2A相析出速率变快,部分MgLi_2A亚稳相分解为AlLi相,同时有AlLi从基体中析出。合金的峰值时效在50℃时效0.5 h时发生,随温度的升高很快发生过时效,其主要原因是AlLi软化相的出现。     

自然时效对6061铝合金锯齿形屈服的影响

对固溶处理淬火后自然时效时间不同的6061铝合金在室温下进行恒定应变率的拉伸试验,研究了自然时效对锯齿形屈服效应(Portevin-Le Chatelier,PLC)的影响。实验发现,材料强度、锯齿周期和临界应变三者在自然时效0~1 h期间均无明显变化,在自然时效超过1 h以后随自然时效时间延长而增大;锯齿幅值在自然时效0~2 h期间随自然时效时间延长而减小,在自然时效超过2 h后趋于稳定值。自然时效过程中,强化效果明显的β'相在自然时效时间1~2h之间开始形成并随自然时效时间线性增加。结合动态应变时效模型的分析结果与实验相符合,揭示了有强化效果的析出相对PLC效应的作用机制:具有强化效果的析出相含量增多将缩短可动位错的等待时间,使得可动位错更难被钉扎,从而导致锯齿周期和临界应变增大。分析结果还表明,该合金中溶质原子主要以体扩散方式向可动位错聚集从而实现对可动位错钉扎。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

The Mirror with Patterns of Auspicious Animals and Grapes——Exquisite cast mirror and the technology of surface tin-enrichment by rubbing-in and infiltration of tin-rich powder

<正>Bronze mirrors were used by the Chinese people before the introduction of the glass mirror.Only after it was replaced by the glass mirror did the bronze mirror gradually retreat from people's lives.Different styles of bronze mirrors were made in different historical periods,particularly in the Warring States Period,the Han and Tang Dynasties,which were the three peaks of the development of bronze mirror arts in ancient China.The casting techniques were exquisite.The surface of the bronze mirror was smooth and bright enough to reflect one's image,and there were scarcely any casting defects on the mirror surface.On the back of the bronze mirror,there were rich depictions of Arts and Humanities,and the ornamentations were also     

The 9th China International Diecasting Congress & Exhibition

The 9th China International Diecasting Congress ＆ Exhibition was held on July 22-24, 2014 at Shanghai New International Expc Centre. This exhibition was the most successful over the years, with over 6890 visitors and 155 exhibitors, and the exhibition area increased by 30% from 9,500 square meters in 2012 to 12340 square meters. Die casting enterprises from a total of 24 countries and regions, including China mainland, Chinese Taiwan and Hong Kong, South Korea, Japan, Germany, India, Thailand, Malaysia, the United States, Russia, Australia, Iran, Ukraine, Brazil, Colombia, Singapore, Austria, Canada, Croatia, France, Turkey, United Kingdom, Vietnam, attended the congress and exhibition.     

Introduction of the Fluid Control Engineering Institute of Kunming University of Science and Technology

正The Fluid Control Engineering Institute of Kunming University of Science and Technology was set up in 1996.The researches of institute concentrate on electro-hydraulic(pneumatic)servo/proportional control and hydromechatronics.The Institute is committed to research and development of electro-hydraulic control of high-end technical equipment in ferrous metallurgy refining produc-     

RARE METALS Volume Contents

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