大晶粒超塑性变形机理的研究

本文通过对供应状态铝锰β-黄铜超塑性的系统研究,探讨了其在大晶粒组织条件下的超塑性变形机理;应用刻痕实验和金相组织观察方法,发现了大量亚晶界和亚晶界的运动。根据实验结果分析和理论计算提出了亚晶界的移动和滑动是大晶粒超塑性变形的主导机制,由测量得知晶界滑动变形对总变形的贡献仅为～10％,这说明晶界滑动是调节机制。     

LC4铝合金在恒应变速率超塑性变形过程中的 m-δ关系及组织演变

原始晶粒平均尺寸为8.7μm 的 LC4合金拉伸试样在515℃和6.7×10~(-3)min~(-1)恒应变速率条件下显示了良好的超塑性,所获得的延伸率达464%。在这种变形条件下,所测得的 m-δ关系曲线属于 m_L=m_(max)型,其最大 m 值为0.78,出现于δ=94%处。该 m-δ关系可表示为δ_I(%)=[C_I×0.0067(~mI~(-0.5)-1]×100在超塑性变形过程中有三种主要的组织演变发生,即扩散蠕变导致邻近晶界的无沉淀区的形成、晶粒的粗化、及空洞的产生。此合金超塑性变形的上述 m-δ关系曲线的形貌可根据超塑变形过程中发生的主要组织演变予以解释。     

时效硬化Cu—1.9Be—0.24Ni合金超塑性变形机制

Cu-1.9Be-0.24Ni 合金的超塑性流动是由晶界滑动、位错滑移和扩散蠕变三种变形机制的相互协调并同时起作用而产生的。位错运动起着协调变形和导致晶界滑动发展的双重作用。扩散过程对晶界滑动也起协调作用。在最佳变形条件下晶界滑动对变形的贡献量最大(ζ=58%)。大量的第二相粒子是有效的位错源。粒子或角隅发射的位错与晶界位错运动(晶界滑动)有相互作用关系;与晶内粒子也有交互作用关系。基于试验结果,文中提出一个时效硬化型超塑性变形机制模型,借以描述 Cu-1.9Be-0.24Ni 合金的变形过程。     

铸态304L奥氏体不锈钢等径角挤压变形研究

 研究了铸态304L奥氏体不锈钢在等径角挤压(ECAP)变形过程中显微组织的演变过程。结果表明，经4道次剪切变形后树枝晶破碎、原始粗大晶粒碎化。显微组织的变化过程可归纳为：原始粗晶粒→晶粒被滑移带分割→位错发展形成高密度位错墙，与滑移带共同作用形成胞块结构→应变增加形成层片状界面→形成大角度晶界的细小晶粒。表明铸态304L奥氏体不锈钢经ECAP变形后塑性变形机制主要由滑移完成。     

铝锂合金电子束焊缝超塑性变形行为与显微组织

通过高温拉伸试验研究了5A90铝锂合金电子束焊接头超塑性变形行为,并采用光学显微镜(OM)对接头变形前后的显微组织进行观察。研究结果表明,5A90铝锂合金电子束焊接头具有良好的超塑性变形能力,接头的延伸率随温度的升高和应变速率的增大而先增大再减小,试样的最佳变形参数为450℃,5×10~(-3)s~(-1),在此参数下试样的延伸率达到最大171.1%。变形后焊缝的组织由细小的等轴枝晶转变为较为粗大的等轴晶,焊缝的变形由扩散导致的晶界迁移和动态再结晶共同协调;而接头热影响区(HAZ)的组织发生较为明显的细化,主要变形机制为动态再结晶。温度的升高和应变速率的降低都有利于增强晶界迁移对焊缝变形的协调作用,同时会造成晶粒的长大,所以温度过高和应变速率过低都会使试样的延伸率下降。     

晶界在超塑性变形中的作用

超塑性材料所具有的微细晶粒组织,意味着材料的单位体积内存在着大量的晶界。本文结合作者及其合作者近几年来所进行的研究工作,详细地论述了晶界在超塑性变形中所起的重要作用。     

含Sc铝镁合金的超塑变形机制

采用透射电镜研究了含微量Ｓｃ元素的ＡｌＭｇ合金在超塑变形过程中的显微组织和位错行为。结果表明：合金在超塑变形过程中发生了四个连续过程：①动态再结晶；②晶界向晶内激发位错；③位错在晶内密集并且受到第二相Ａｌ３Ｓｃ质点的阻碍作用，同时通过攀移越过晶内弥散分布的Ａｌ３Ｓｃ粒子；④位错向晶界运动并在晶界处消失。动态再结晶是合金在超塑变形中存在的组织效应，起到了细化晶粒，诱发微细晶超塑性的作用。该合金超塑变形的主要机制为晶界滑动伴随晶内位错运动     

细晶Ti-6Al-4V合金的超塑性变形行为与组织演变

对不同温度下退火处理后的细晶TC4合金板材进行超塑性拉伸变形,研究该合金在750~850℃,应变速率为3×10-4~1×10-3 s-1条件下的超塑性拉伸变形行为,分析晶粒尺寸、变形温度和β相含量对合金性能的影响。结果表明:退火后的(α+β)型细晶Ti-6Al-4V合金表现出良好的超塑性,并且晶粒越细,最佳超塑性变形温度越低。晶粒直径为2.5μm、β相含量(体积分数)为9.6%的TC4合金在温度为800℃、应变速率为1×10-3 s-1的变形条件下,伸长率最大,达到862%。不同晶粒度合金的应变速率敏感系数m均随变形温度升高先上升后下降,最高达0.61。β晶粒处于α晶粒三叉晶界处,升温或拉伸变形时聚集并沿α晶界长大,形成细长的β晶粒并逐渐变粗大,因此在900℃以上高温下合金的超塑性变形能力降低。     

ZnAl_(5-0.03)合金超塑性的研究(Ⅳ)——超塑性变形过程中显微组织的变化

ZnAl_(5-0.03)合金超塑性变形过程中晶粒的热长大是次要的,而变形量能有效地促进晶粒长大,在大变形量的条件下还伴随着呈现孔洞。提高应变速率使晶粒细化,组织微粒化,在高应变速率下呈现孔洞,继续提高应变速率会使孔洞发展。本文还讨论了变形过程中显微组织变化规律与超塑性力学行为间的关系。     

TA15钛合金超塑性变形时的组织演变

研究了TA15钛合金超塑性变形后显微组织的演变及变形条件对超塑性变形行为的影响。结果表明:在变形温度为850~950℃、应变速率为1×10-4~1×10-3s-1超塑性拉伸时,TA15钛合金表现出良好的超塑性变形性能,且在900℃,5.5×10-4s-1变形条件下,延伸率最大为803.3%。在应变速率不变的条件下,随着变形温度的升高,α相晶粒尺寸增大,β相含量增加,晶粒仍保持细小、等轴状态。在变形温度一定时,随着应变速率的降低,α相晶粒尺寸增大,β相含量增加。同时变形程度对显微组织有显著影响,拉伸后不同部位的显微组织均有一定程度的粗化,变形程度越大,晶粒粗化的越明显,并伴有α相到β相的转变。变形过程中,加工硬化与变形软化相互竞争,表现为传统超塑变形的稳态流动特征。     

Acceleration of Electricity Reform Brings Benefit to Big Electricity Users,Aluminum Manufacturers Can Save Costs Up to Several Hundred Million

<正>Recently the National Commission of Development and Reform again assembled experts to solicit opinions,and discussed new electricity reform program.According to information disclosed by experts attending the meeting,in the future electricity reform will undergo top-down design,possibly a     

Qinghai's Aluminum Processing Capacity to Rise at the End of the Year

正Since the release of Implementation Opinions on Carrying out‘Guiding Opinions of the State Council on Resolving Serious Production Overcapacity Conflicts’,according to the actual situation of industry,Qinghai has focused on electrolytic aluminum,cement,ironsteel(including iron alloy and silicon carbide),     

Recent Trends in China's Copper Scrap Market-Part Ⅱ

<正>2.Tianjin Scrap Metal Market In Tianjin,we mainly visited Jinghai Ziy Town scrap market and Binhai New Area’some copper scrap enterprises and enterprise using copper scrap.In Ziya we felt the coppe scrap market was particularly deserted,mos copper scrap enterprises in the town wer closed,industry insiders said in 2012 the plac here was bustling with activity.According to     

Shanghai Clearing House to Roll out Renminbi-denominated Copper Clearing Operations in Free Trade Zone

正Clearing House Financial Markets Co.,Ltd.(Shanghai Clearing House)General Manager Xie Zhong told the media recently at the briefing of the international symposium of"Reform Deepening and Mechanism Innovation of the Post-crisis Kerb Market",Shanghai Clearing House will explore the feasibility of carrying out bond business in     

Development and Application of New Materials for Copper Processing in China

正After over 60 years of developmnt,a system for RD and production of copper processing materials has already taken shape in China.After the reform and opening-up,the application of copper processing materials has gradually expanded from the military industry to civil field.The annual output of copper     

China’s Mineral Exploration Market Downturn Causes Decline of Investment in Bauxite

<正>According to a survey report conducted recently by China Geological Survey Development Research Center,in the first half of 2014,China’s mineral exploration market continued to decline,with the investment in exploration of non-fuel minerals dropping by13.7%and drilling workload dropping by21.7%.According to statistical analysis of the Center,     

Chinalco and China National Administration of Coal Geology Jointly Built Guangxi Rare Earth Industrial Base

正On June 3,Chinalco and China National Administration of Coal Geology signed cooperation agreement for strategic cooperationcooperation agreement between Chinalco Guangxi Nonferrous Rare Earth Development Company and Xuzhou Jin Shi Pengyuan Rare Earth Material Factory.According to the agreement,both sides would jointly support Chinalco Guangxi Nonferrous Rare Earth Development Company and Xuzhou Jin Shi Pengyuan Rare Earth Material Factory to carry out comprehensive cooperation covering rare     

Aluminium Production by Province or City in 2014

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Fabricated Copper Production by Province or City in 2014

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Zinc Production by Province in 2014

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