添加Mn对6061铝合金结晶相和力学性能的影响

为了探讨通过微合金化改善、提高铝合金组织和性能的方法,通过扫描电镜/能谱、X射线衍射分析及力学性能测试,研究了微合金化元素Mn添加量对6061铝合金热处理前后结晶相和力学性能的影响。结果表明:铸态组织中,β-Al_5FeSi相随Mn含量的增多逐渐减少,α-Al_8Fe_2Si相随Mn含量的增多逐渐增多;均匀化处理后,Mn含量在超过0. 21%后,β→α相的转变基本完全完成,Mn含量达到0. 78%,颗粒状α-Al_8Fe_2Si相明显增多; T6处理对粗大鱼骨状的α-Al_ Fe Si相形貌改变不大,但能使短棒状的Mg_2Si相得以完全回溶,使比较细小的结晶相如针状β-Al_5FeSi相向颗粒状α-Al_8Fe_2Si相转变; Mn含量为0. 21%时,铸态和T6态的强度和塑性均达到良好配合,T6态力学性能表现为R_m=348 MPa,R_(p0. 2)=310 MPa,A=3. 0%。     

一种Al-Mg-Si-Cu合金的铸态组织研究

采用金相显微镜（OM）及扫描电子显微镜（SEM），研究了Al-0．44Mg—1．15Si-0．32Cu-0．11Fe-0．11Cr-0．07Mn合金的铸态、均匀化组织，并对合金在凝固过程及均匀化退火后形成的相进行了分析。结果表明：合金的铸态组织中主要存在α—Al、Mg2Si、Si、β-Al5FeSi、α-Al（MnCr）FeSi、CuAl2和Al5Cu2Mg8Si6（Q）等相。均匀化退火后，Mg2Si、CuAl2和Q相消失，Si相聚集分布在晶界处。同时针状的β-Al5FeSi转变为颗粒状α-Al（MnCr）FeSi相，材料的组织得到改善。     

普通碳锰钢的超细晶板材控轧工艺研究

在GLEEBLE2000热模拟试验机上进行普通碳锰钢Q345两相区变形实验，研究变形工艺条件对材料微观组织的影响，分析其组织演变规律及机理，斤且在实验轧机上进行板材轧制实验。结果表明，实验钢(0．16C，0．3Si，1．29Mn)采用在过冷奥氏体区及其邻近的两相区变形可以获得等轴超细晶铁素体组织；控轧获得的9mm板材铁素体晶粒细化到晶粒截距4μm，屈服强度达到458MPa，抗拉强度580MPa，伸长率29％。     

不同Mn含量低碳钢过冷奥氏体形变过程中的铁素体相变

通过热模拟压缩实验,对C,Si含量基本相同、Mn含量不同的低碳钢过冷奥氏体在形变温度760℃,形变速率1/s条件下单向压缩变形过程中的组织演变进行研究,分析了Mn对低碳钢过冷奥氏体变形特征、转变动力学特征以及形变强化相变铁素体晶粒细化的影响。结果表明,Mn延迟低碳钢形变强化相变的进行,Mn含量提高,完成相变所需总应变相应提高,形变强化铁素体转变动力学可分三个阶段,随Mn含量增加,各阶段所需时间延长,应变提高,通过形变强化相变,Mn含量(质量分数,％)为0.48,0.84和1.29三种钢可获得平均晶粒截径分别为3.57±1.60,2.00±1.05和2.29±1.02μm的微细等轴铁素体晶粒以及第二组织弥散分布的复相组织。     

Mn和Sn对Sr变质、Al-5Ti-B晶粒细化Al-7Si-Mg合金显微组织的影响（英文）

研究Mn与Sn对Sr变质、Al-5Ti-B晶粒细化Al-7Si-Mg合金显微组织的影响。结果表明,合金添加高含量Sr后具有柱状树枝晶结构,Al-5Ti-B晶粒细化剂发生了毒化现象:TiB_2颗粒偏聚在共晶Si区域,并发现Sr金属间化合物在TiB_2颗粒上分布。讨论了Sr毒化现象的机理。此外,添加Mn元素会使合金的富铁相结构从β-Al_5FeSi向α-Al(Mn,Fe)Si转变。随着Mn含量的增加,α-Al(Mn,Fe)Si相从树枝状转变为树枝状分布的小棒状,最终转变为汉字状结构。透射电镜(TEM)观察显示,Mg相对于Si更倾向于与Sn反应,Mg_2Sn在Si/Si界面或Al/Si界面上析出。     

Al-0.8Mg-1.0Si-0.7Mn合金均匀化热处理工艺

采用光学显微镜、差热分析、扫描电镜、能谱分析,研究了Al-0. 8Mg-1. 0Si-0. 7Mn合金的铸态组织以及铸锭经不同均匀化制度处理后的微观组织。结果表明,试验合金的铸态组织中主要存在Mg2Si相和Al(Fe Mn) Si相,同时存在少量的Al Cu MgSi相和Al Mn相;铸锭过烧温度为589℃;铸锭经560℃保温24 h均匀化处理后,组织中Mg2Si相回溶充分,含Fe相发生了球化,同时在均匀化过程中析出了一种含Mn相。工业化生产条件下,宜采用560℃保温24 h的均匀化处理工艺。     

Sc对AlMg5Si2Mn合金组织与力学性能的影响

研究了Sc含量对铸态AlMg5Si2Mn合金的显微组织,力学性能和断裂特征的影响。结果表明,添加适量的Sc对AlMg5Si2Mn合金中的初生α-Al和共晶Mg_2Si具有显著的变质效果。随着Sc含量从0增加到0.25%,初生α-Al形貌由较大的块状转变为细小的球状,共晶Mg_2Si的形貌由汉字状转变为纤维状或点状。Sc在合金中形成Al_3Sc相,作为异质形核基底促进初生α-Al形核,并晶粒细化。Sc原子富集在共晶Mg_2Si相的生长前沿形成成分过冷,Mg_2Si相的生长被抑制。Sc的添加可以提高合金的抗拉强度和伸长率,与未变质合金相比,添加0.15%～0.25%Sc的合金拉伸性能最佳,抗拉强度和伸长率分别提高了20.9%和60.4%。     

Al-5Mg-0.8Mn合金的凝固组织研究

通过重熔-凝固试验,研究了接近AA5083合金成分的Al-5Mg-0.8Mn合金的凝固组织。结果表明:Fe和Si元素对Al-5Mg-0.8Mn有重大影响,促进了金属间化合物Al_6(Fe,Mn)和Mg_2Si的形成。当Fe、Si含量很低时,Al-5Mg-0.8Mn合金的凝固组织非常简单,只是在α-Al基体上零星散落着一些细小的Al_6(Fe,Mn)共晶相。当Fe、Si含量较高时,合金中不但出现了大量粗大的Al_6(Fe,Mn)和Mg_2Si共晶相,而且,共晶相Al_6(Fe,Mn)呈现多种不同的形态,而Mg2Si相主要呈汉字状。     

基于共晶相量化的6082铝合金的最佳均匀化制度

采用差示扫描量热仪、金相显微镜、扫描电子显微镜及能谱分析等方法,通过对6082铝合金的铸态和均匀化态的显微组织观察和共晶相的量化统计研究,确定了6082铝合金的最佳均匀化制度。结果表明:6082铝合金铸态组织中存在着大量的非平衡凝固的Mg2Si共晶相和β-Al(Mn,Fe) Si相共晶相。经过560℃10 h均匀化后,Mg2Si共晶相溶解入α(Al)基体中,β-Al(Mn,Fe)Si共晶相向α-Al(Mn,Fe)Si相转变。     

3104合金均匀化过程中金属间化合物的演变

利用金相显微镜、扫描电镜等对不同温度、不同时间均匀化的3104合金中化合物的转变情况进行研究。结果表明,3104合金铸锭组织中的粗大化合物主要为(Fe Mn)Al_6相,少量为α-Al_(12)(Fe Mn)_3Si相,其相对比例10%。均匀化过程中(Fe Mn)Al_6相向α-Al_(12)(Fe Mn)3Si相转变,随温度升高和保温时间延长,α-Al_(12)(Fe Mn)_3Si相比例增加,在580和600℃保温20 h后,α-Al_(12)(Fe Mn)_3Si相比例达80%以上。转变过程中,α-Al_(12)(Fe Mn)_3Si相中产生细小密集的铝点,随时间延长铝点合并而变得粗大稀疏。同时,晶粒内析出Al_(12)Mn_3Si弥散相,500℃均匀化时弥散相尺寸细小密度最大。随温度升高,弥散相尺寸增大密度减小,580和600℃保温后弥散相尺寸粗大,分布稀疏。因此,580和600℃均匀化可以获得较合理的化合物比例和弥散相分布。     

Self-diffusion of Ni in B2 type intermetallic compound NiAl

Combining molecular dynamic (MD) simulation with modified analytic embedded-atom method (MAEAM) potential, the formation, migration and activation energies of Ni self-diffusion in intermetallic compound NiAl have been calculated for five diffusion mechanisms, NNN jump, [1 1 0] 6JC, straight [1 0 0] 6JC, bent [1 0 0] 6JC and triple-defect diffusion. The results show that the Ni self-diffusion is dominated by the triple-defect diffusion mechanism since it requires essentially the lowest migration or activation energy (Q = 2.769 eV) in the five diffusion mechanisms. This is consistent with the conclusion of Frank et al.     

不同异种钢管道焊接接头残余应力的数值模拟

利用有限元软件ABAQUS,开发了一个顺次耦合的热应力有限元计算程序,对0Cr18Ni9/20和1Cr5Mo/20异种钢焊接接头残余应力进行了有限元模拟分析.结果表明,无论是采用奥氏体不锈钢焊条A302焊条还是镍基焊条Incone182焊条,0Cr18Ni9/20钢和1Cr5Mo/20钢焊接接头中最大的轴向残余应力和环向残余应力产生在20钢侧的热影响区,0Cr18Ni9侧有最小的焊接残余应力.采用Incone182来代替A302可以有效地降低残余应力值,提高抗应力腐蚀开裂的能力.     

基于薄壁梁落锤压溃高强钢动态力学性能分析

先进高强钢对汽车的安全性和轻量化具有重要影响,其动态力学性能直接影响到整车碰撞安全。针对汽车用先进高强钢的动态力学性能进行分析,选取双相高强钢HC500/DP780,分别采用普通力学拉伸试验机和液压伺服高速拉伸试验机,获得0.001和0.1 s~(-1)的2种准静态下以及1,10,100,200,500和1000 s~(-1)的6种高应变速率下的单向拉伸试验力学性能,并基于Johnson-Cook方程获得材料的动态力学本构模型。基于薄壁梁落锤压溃试验平台进行压溃性能分析,并采用LS-DYNA进行模拟仿真分析,以此对材料动态力学性能数据及本构模型进行验证分析。结果可知:模型仿真与试验分析的变化趋势基本一致,表明模型仿真的准确性,进而说明材料动态力学性能及本构模型的准确性;随着碰撞速率的增加,管件的吸能比以及载荷比都在减小,这说明碰撞速率对管件的吸能特性有一定影响,随着碰撞速率增加,管件的吸能特性逐渐降低。     

模具间隙对高强度钢热冲压过程的影响

利用DEFORM软件,建立了不等模具间隙下高强度钢板热冲压的有限元模型,研究了模具间隙对22Mn B5钢板热冲压成形中温度场以及马氏体转变的影响规律。数值模拟结果表明:模具间隙是影响板料温度变化的主要因素,板料的最大温差随着模具间隙先增大后减小;模具间隙为0.95t~1.00t时,板料各部位的马氏体分布均匀,转变率高。在此基础上,进行了热冲压试验,测试了板料侧壁位置点和底部圆角位置点的温度变化,并观察了板料成形后的微观组织,通过试验结果与数值模拟结果一致性对比,验证了数值模拟结果的可靠性与准确性。     

Cellular automaton model for simulation of metastable pitting

Abstract

As a new simulation method, cellular automata (CA) approach had been used in a number of areas, including electrochemistry and corrosion science research. In this work, a probability CA model was developed to simulate the growth of metastable pits. The simulation imaged the morphology of the pit and calculated the time dependences of pitting current and pitting current density. Results demonstrated that the CA approach is capable of simulating corrosion pit in terms of the pit morphology and pit growth kinetics. During growth of a hemispherical metastable pit controlled by diffusion, the time dependence of pitting current follows I?=?f(t²) law. Furthermore, it is determined that, for the simulation results to be consistent with the experimental results, an optimal range for variable d should be 0·1–0·25.     

Effect of plane strain on microstructures and texture, through the reduction ratio of AZ31 Mg alloy

Structural evolution of warm-rolled AZ31 alloy sheets was investigated with respect to various reduction ratios. In order to examine the effect of rolling pass on deformation of the sheet, one-pass rolling was applied to the AZ31 alloys for various 6/1/2011reduction ratios. When the applied reduction ratio was ∼85% of the initial thickness, significant grain refinement and texture development were achieved with dynamic recrystallization. Moreover, with the increase of the rolling reduction ratio from 30% to 85%, the warm rolled sheets exhibit plane strain mode displaying uniform 〈0 0 0 1〉//ND basal textures throughout the whole sheet thickness. The two-dimensional finite element method simulation showed that the current lubrication rolling results in a uniform plane strain deformation through the whole warm rolled sheet.     

Diffusion behavior of W in the WCu/Ni interface

In order to clarify the W diffusion behavior at the WCu/Ni interface, a WCu/Ni diffusion couple was prepared, and the phase structure and constituents of the diffusion layer were characterized by a scanning electron microscopy and transmission electron microscopy. Based on the experimental data, the interdiffusion coefficient was calculated. The diffusion behavior was also verified by the simulation according to the first principle method. The results show that a diffusion layer with the thickness of 1 μm, which is composed of Cu rich solid solution and W rich solid solution, is formed on the surface of W particles. The interdiffusion coefficient of W in the transitional layer is 3.381 × 10⁻¹⁵ cm²/s, which is much larger than that of W in Ni. This is in good agreement with the simulation result.     

压铸镁合金微观组织模拟

采用CellularAutomaton微观模型 ,对压铸镁合金的三维微观组织演变进行了模拟。在模拟过程中 ,采用连续形核模型处理液态金属的异质形核现象 ,通过正态分布函数描述形核质点密度随温度的分布关系 ,在给定过冷度时对分布函数积分可得到该时刻的形核密度 ,晶粒生长模型则考虑了枝晶尖端生长动力学和择优生长方向 <10 10 >,也考虑了温度场的影响 ,并完成了宏观温度场和微观计算的耦合。最后通过压铸镁合金标准拉伸试棒金相试验 ,对模拟结果进行了验证 ,试验结果和模拟结果在平均晶粒尺寸方面符合较好     

Mechanism and modeling of saw-tooth structure formation in the L12–L10 two-phase system

The strain-accommodating mechanism of formation of the saw-tooth microstructure in the L1₂+L1₀ two-phase ordered system is proposed. To describe the atomic scale kinetics of ordering and decomposition in this system, the master equation, which explicitly incorporates the effect of the transformation strain, is formulated. It is used to simulate the precipitation of the L1₀ phase from the L1₂ parent phase in the Co–Pt alloy. The computer simulation shows that the decomposition occurs heterogeneously on antiphase boundaries of the L1₂ structure if the composition is near the solubility limit of the L1₂ phase. It eventually produces the saw-tooth microstructure. The decomposition transforms the (010) antiphase boundary into a layer of the single-variant tetragonal L1₀ phase separating the L1₂ antiphase domains. Later, the strain accommodation transforms this single-variant L1₀ phase layer into the saw-tooth pattern. The simulation results are in excellent qualitative and quantitative agreement with our TEM images of Co_38.5Pt_61.5.     

Electrochemical investigation and modeling of corrosion inhibition of aluminum in molar nitric acid using some sulphur-containing amines

Chemical and electrochemical measurements incorporated with quantum chemical calculations and molecular dynamics simulations were used to study the corrosion inhibition characteristics of some thiosemicarbazone derivatives on the inhibition of aluminum corrosion in 1.0 M HNO₃. Polarization curves demonstrated that the thiosemicarbazone derivatives were of mixed-type inhibitors. EIS plots indicated that the addition of thiosemicarbazone derivatives increases the charge-transfer resistance of the corrosion process, and hence the inhibition performance. The molecular dynamics simulation results show that the three thiosemicarbazone derivatives can adsorb on the A₂O₃ (1 1 1) surface through the sulphur and nitrogen atoms as well as π-electrons in the pyridyl structure.