AlSi10Mg的激光选区熔化成形研究

利用激光选区熔化(selective laser melting,SLM)成形技术对Al Si10Mg铸造铝合金的成形进行了工艺研究,获得了致密的成形,并对其沉积态和热处理态试样进行了静态拉伸性能测试和显微组织分析。结果表明:对于Al Si10Mg,其SLM沉积态的常温拉伸强度远高于铸件标准,延伸率与铸态相当;退火工艺对SLM试样的组织及力学性能有着重要的影响,随着退火温度的提高,试样微观组织发生改变,在300℃、2 h退火工艺下,原本均匀分布的颗粒状Si聚集长大为针状,使得试样的强度下降,延伸率升高。抗拉强度由沉积态的507~518 MPa下降到378~406 MPa,延伸率由沉积态的3.0%~3.5%增加到6.5%~9.5%。     

AlSi10Mg铝合金3D打印组织与性能研究

采用激光选区熔化技术探索3D打印方法制备航空航天用Al Si10Mg铝合金的可行性,并对其性能适用性进行评价。研究发现:选区激光熔化技术成形Al Si10Mg合金组织致密,晶粒细小,力学性能优于传统铸造成形的零件。其中横向性能和纵向性能相当,横向塑性略优于纵向。使用国产SLM设备成形的Al Si10Mg合金退火态性能与德国EOS公司的官方性能数据相当,说明国内对于金属3D打印的研究和应用水平已达到国际先进水平。     

激光功率对5356铝合金激光诱导MIG电弧增材制造组织性能的影响

为了改善MIG电弧增材制造5356铝合金的组织及力学性能,将低功率激光与MIG电弧增材制造结合,采用低功率脉冲激光诱导MIG电弧增材制造技术进行了不同激光功率下5356铝合金单道多层墙体成形试验,分析了激光功率对沉积态5356铝合金组织、显微硬度及拉伸性能的影响.结果表明,低功率脉冲激光诱导MIG电弧增材制造成形试样整体冶金结合良好、无明显的未熔合现象.墙体的微观组织主要呈等轴晶状,与单MIG电弧堆积的墙体相比,等轴晶变得细小均匀,显微硬度提高,波动较小.加入激光可以减少Fe元素、Si元素含量和气孔数量,使墙体的力学性能提高,当激光功率为300 W时达到最大值,较单MIG电弧堆积墙体的抗拉强度提高了12.0%.     

激光立体成形AlSi10Mg合金的微观组织及力学性能

激光立体成形已逐渐成为大型高性能复杂铝合金构件制造的一条重要途径。采用具有不同波长的CO_2和YAG激光器在铸态基材上进行了AlSi10Mg合金的激光立体成形,研究了不同激光器对AlSi10Mg合金沉积态和T6热处理态下的微观组织和力学性能的影响。利用XRD、OM和SEM研究了AlSi10Mg合金成形件的微观组织;利用电子拉力试验机测试了AlSi10Mg合金成形件的力学性能。结果表明:相比铸态基材,AlSi10Mg合金沉积态组织主要由100取向沿沉积方向外延生长的柱状α-Al枝晶和枝晶间呈纤维或颗粒状生长的Al-Si共晶组成,组织显著细化;且在530℃,3~5 min固溶处理后可实现共晶Si的球化。与CO_2激光相比,采用更短波长的YAG激光进行成形时组织更为细化。经T6热处理后,采用YAG激光成形的AlSi10Mg合金力学性能明显优于压铸铝合金。     

激光熔化沉积AlSi10Mg及气孔对力学性能的影响

采用激光熔化沉积的方法对AlSi10Mg增材制造,制备出致密度大于99%、抗拉强度350 MPa左右、延伸率8%的薄壁墙体试件,利用光学显微镜与扫描电镜分析了沉积态的组织。发现即使增材制造过程水氧含量（体积分数,下同）均控制在1×10^-5以下,试件内部仍存在一定的气孔缺陷,气孔均为直径100 μm以下的氢气孔。进一步试验表明,环境中的氧体积分数与气孔率呈正相关关系。在保持环境湿度和温度不变的情况下,环境氧含量由1×10^-5增加到1×10^-3,气孔直径略微增大,气孔率由0.45%增大到2.71%,气孔率增加近5倍,同时抗拉强度降低100 MPa左右,降幅超过30%,延伸率降幅超过20%。最后探讨了氢气孔在激光熔化沉积制造的试件中产生的机理,给出了利用激光熔化沉积工艺制备稳定的AlSi10Mg合金的策略。     

SLM成形WC/Al基复合材料的显微组织与力学性能

采用物理方法混合纳米WC与AlSi10Mg铝合金粉末,利用选区激光熔化成形技术(SLM)制备WC/Al基复合材料试样。通过金相显微镜、扫描电镜、拉伸试验等对比同种工艺制备的AlSi10Mg试样及WC/Al基复合材料试样的性能,分析纳米WC对其微观组织形成、演变及力学性能的影响。结果发现,复合粉末球形度好,粒度分布均匀。WC/Al基复合材料试样硬度(HV)约为158.9,屈服强度达到337.8 MPa,抗拉强度高达514.0 MPa,相比沉积态试样分别增加了14.6%、4.7%、6.3%。     

5356铝合金TIG电弧增材制造组织与力学性能

采用钨极惰性气体保护焊(TIG)电弧增材制造工艺制备5356铝合金成形件,并对成形件的组织和力学性能进行研究.结果表明,5356铝合金增材制造的相组成为α-Al基体和β(Al3Mg2)相;随沉积高度增加,沉积层显微组织由等轴晶向柱状晶转变,达到热平衡状态后趋于稳定,这是因为增材制造具有热积累效应;最顶层组织呈现树枝状,且Mg元素偏析严重;中下部组织形态多样,包括等轴晶组织、柱状晶组织及其混合组织,同时Mg元素偏析得到改善.力学性能测试结果显示,随沉积高度的增加,层内显微硬度先降低后趋于稳定,这是因为沉积层组织在增材制造过程中经历逐渐粗化的过程,导致显微硬度下降,达到热平衡状态后显微组织相对稳定,显微硬度也趋于稳定.沉积层层间位置的硬度大于层内,这是因为层间结合处为细小的等轴晶组织.聚集在层间的气孔可能是导致薄壁件屈服强度低于理论计算值的原因.抗拉强度、屈服强度以及伸长率都表现了各向异性,横向拉伸性能优于纵向,这是因为薄壁件层间气孔聚集以及显微组织不均匀.     

喷射成形70Si30Al合金在加热保温过程中显微组织的演变规律

利用喷射成形技术制备了70Si30Al合金新型电子封装材料,研究了沉积态合金的显微组织及其随温度变化的规律。结果表明:沉积态70Si30Al合金显微组织细小,初生硅相为不规则的块状,均匀弥散分布,初生硅相之间主要是过饱和α(Al)相和铝硅伪共晶相;70Si30Al合金在620℃以下保温90 min,初生硅相没有明显长大,但随着温度的升高出现球化现象,过饱和α(Al)相没有显著变化,铝硅伪共晶相在566~582℃之间熔化,随着温度的升高,熔化相增多并互相凝聚在一起;合适的喷射成形70Si30Al合金热加工变形温度为560~590℃。     

SLM激光快速成型Al-Si合金组织及力学性能分析

采用选择性激光熔化(SLM)快速成型工艺制备出Al Si10Mg合金试样。利用金相显微镜(OM)和扫描电镜(SEM)分析了不同热处理工艺对Al Si10Mg合金试样微观组织的影响,并对Al Si10Mg合金试样进行拉伸试验测定。结果表明,通过适当热处理后的试样晶粒细小,组织均匀致密,气孔缺陷明显减少。Al Si10Mg合金试样较铸造铝合金具有更好的综合力学性能。     

基体表面粗糙度对激光沉积不锈钢形貌、组织及性能的影响

目的研究基体待沉积表面粗糙度的变化对激光沉积之后沉积层质量(宏观形貌、微观组织和力学性能)的影响,从而获得形貌、组织及性能优良的沉积层。方法采用316L不锈钢粉末,在不同表面粗糙度状态下P20钢基体表面分别进行单道单层、薄壁、多道搭接及块体沉积实验,获得测试分析所需沉积层,基于OM、SEM以及拉伸试验对沉积层组织性能进行分析。结果单道单层时,相对于铣削基体表面沉积层,喷砂基体表面沉积层的熔高、熔深增加幅度达到了100%,而熔宽增加较平缓;单道薄壁时,在前5层的沉积中,喷砂基体表面沉积高度增长达到2.5mm,铣削表面沉积高度仅为前者一半,喷砂基体上沉积层内部孔隙率仅为铣削基体的31%;多道搭接时,随着粗糙度的增大,沉积层截面纵向尺寸H的内部增长范围持续变大,而横向尺寸L范围保持稳定。喷砂基体表面沉积层的σ_b为540.93 MPa,而铣削基体上的σ_b为523.12 MPa。结论随着基体表面粗糙度的增加,沉积过程中陷光效应相应增强,单道单层沉积层的宏观形貌尺寸随之增大。对于薄壁沉积,基体粗糙度对薄壁高度的影响主要集中在前5层,粗糙度的增大使得沉积高度生长加快,内部孔隙率减小。多道搭接时,粗糙度越大,熔高熔深方向的尺寸变化越大,沉积层内部枝晶更加粗大,且不均匀。沉积层内部的抗拉强度随粗糙度的增大而提升。     

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.     

Effect of Short-Time Aging on the Pitting Corrosion Behavior of a Novel Lean Duplex Stainless Steel 2002

The effect of short-time aging in the temperature range between 400 and 1000 °C on the pitting corrosion behavior and mechanical property of a novel lean duplex stainless steel(LDSS) 2002 was investigated through the potentiostatic critical pitting temperature(CPT) tests and the Charpy impact tests. Both the pitting corrosion resistance and the toughness of aged specimens degraded due to the precipitation of detrimental secondary phases and the most significant reduction of CPT and impact energy emerged at 650 °C concurrently. The CPT of LDSS 2002 specimen aged at 650 °C decreased by 28 °C, and the impact energy dropped from 69 to 29 J/cm~2 compared with the solution-annealed sample. Transmission electron microscopy characterization showed that the main precipitates in LDSS 2002 were Cr_2N and M_(23)C_6 along the ferrite–austenite grain boundaries.     

INTRODUCTION TO PATENTS

The invention provides a method of making a mold which can reduce SOx generation rate while preventing decrease in hardening rate in the case of using sulfuric acid for a hardener composition. The method has a mixture step in which fire-resistant particles, a hardener composition and a binder composition are mixed to obtain a composition for a mold. The hardener composition contains sulfuric acid. In the mixture step, sodium carbonate is added. A molar ratio of the sulfuric acid to the sodium carbonate is 0.5 or more and 4.0 or less.     

China Foundry Week 2014

China Foundry Week, hosted by the Foundry Institution of Chinese Mechanical Engineering Society （FICMES） each year, is a large academic event in China. It is one of the ten high-impact activities sponsored by the Chinese Mechanical Engineering Society.     

17th Conference of Hydrodynamic and Electromechanical Control Engineering Call for papers

正1.Contents In order to promote the academic exchanges and technical communication of the research in the field of fluid power transmission and control,fluid control engineering specialized committee of the Chinese Society of Theoretical and Applied Mechanics will hold the 17th Conference of Hydrodynamic and Electromechanical Control Engineering on July 27-29,2014 in Tibet,Lhasa city.     

Information for Contributors

正The Transactions of Nonferrous Metals Society of China,founded in 1991 and sponsored by The Nonferrous Metals Society of China,is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology,including mineral processing,extraction metallurgy,metallic materials and heat treatments,metal working,physical metallurgy,powder metallurgy,with the emphasis     

Preface

<正>We are pleased to present this Special Issue of Transactions of Nonferrous Metals Society of China containing selected papers from the First Asian Conference on Aluminum Alloys(ACAA-2013),held in Beijing,China,13–17 October 2013.This conference has been initiated,with approval of     

Information for Contributors

The Transactions of Nonferrous Metals Society of China, founded in 1991 and sponsored by The Nonferrous Metals Society of China, is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology, including mineral processing, extraction metallurgy, metallic materials and heat treatments, metal working, physical metallurgy, powder metallurgy, with the emphasis on fundamental science. It is the unique preeminent publication in English for scientists, engineers, under/post-graduates on the field of nonferrous metals industry. This journal is covered by many famous abstract/index systems and databases such as SCI Expanded, Ei Compendex Plus, 1NSPEC, CA, METADEX, AJ and JICST.     

FORMULAS OF TENSION OF CONTINUOUS ROLLING PROCESS

The development of computer controlled continuous rolling process calls for a mathematical expression that can express the inequality condition of "constant flow". Tension is the link of the continuous rolling process. From the condition of dynamic equilibrium, a differential equation of tension is given out. On the basis of the physical rules established from the industrial practice and experimental studies, the law of volume constancy, the linear relation of forward slip and tension, the state equation of continuous rolling, the formula of dynamic tension, and the formula of static tension have been obtained. These formulae reflect the functional relations between tensions, thickness, roll velocity, and time in the continuous rolling process. It is implied that the continuous rolling process is a gradually steady, controllable, and measurable dynamic system. An assumption of predicting the thickness of a steel plate using these tension formulae is also put forward.     

Bulletin of the Awards in 2013

<正>Five reviewers and 9 published articles are selected as the Excellent Rewewerand Excellent Article in 2013 respectively.Excellent Reviewers:Prof.Z ongyi Ma(Institute of Metal Research,CAS,C hina);Prof.Y ongbo Xu(Institute of Metal Research,CAS,C hina);Prof.Guangping Zhang(Institute of Metal Research,C AS,C hina);Prof.Z hendui Cui(Tianjin University,China);