晶粒组织对2195铝锂合金应力时效析出行为与性能的影响

本文通过恒应力蠕变拉伸、室温拉伸及慢应变速率拉伸应力腐蚀性能测试等试验,结合OM、SEM、TEM及EBSD等组织观察,分析探究变形和细晶两种不同晶粒组织对应力时效处理2195铝锂合金析出行为与性能的影响。结果表明：与细晶组织板材相比,变形组织板材达到峰值硬度的时间由18h缩短至4h,峰值硬度由165.3HV升高到228HV,抗拉强度由584.6MPa提升至641.9MPa。通过计算细晶强化、位错强化及析出相强化对合金强度提高的贡献值,发现变形组织板材力学性能提升主要来源于位错强化的贡献。同时,与细晶组织板材相比,变形组织板材的 ISSRT值由7.6%降低到4.8%,应力腐蚀敏感性降低。变形组织板材的大角度晶界比例由细晶组织板材的64.6%降低至41.1%,晶界析出相分布更为离散,几乎观察不到无沉淀析出带,是获得较为优异抗应力腐蚀性能的主要原因。     

Special features of strain aging of sheet automobile IFBH steel

Strain aging of commercial sheet automobile IF steels is investigated. The aging process is studied by measuring the dynamic modulus of elasticity, the amplitude-independent dislocation internal friction, the mechanical properties, and the microhardness. Analysis of the results obtained reveals the complex mechanism of strain aging of the steels. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 1, pp. 38–45, January, 2007.     

正方形薄板激光三维成形球冠面的应力场分析

激光成形是利用激光束的能量修整板材曲率的一种新型柔性无模成形加工方法。为了描述激光三维成形中的弹塑性变形过程,以进一步揭示其三维成形的机理,文章采用显式动力学方法分析了交叉线扫描激光三维成形正方形薄板为球冠面的物理过程,揭示了激光扫描过程中正方形薄板的温度场、应力场、应变场的变化情况,虽然激光引起薄板温度变化产生的热应力仍是三维成形的主要因素,但是激光三维成形与激光直线扫描成形不同,激光三维成形扫描过程中在薄板内部形成的应力波是影响激光三维成形的主要因素之一,薄板的应变、变形等均与应力波有关,本文揭示的物理行为为下一步的机理研究打下了良好的基础。     

Strength and structure variation of 2195 Al-Li alloy caused by different deformation processes of hot extrusion and cold-rolling

2195 Al-Li alloy was deformed through extrusion followed by cold-rolling. The textures of the extruded plate and cold-rolled sheet after solutionization were investigated. The longitudinal strength and precipitates after T8 aging were measured and observed, respectively. Compared to those in the sheet, T1(Al₂CuLi) precipitates in the extruded plate after T8 aging are non-uniform, and their incubation time is shorter. The extruded plate after solutionization is not recrystallized and contains 55.28% deformation textures of Brass and S. In the cold-rolled sheet after solutionization, massive recrystallization occurs and S component disappears. Due to the higher fraction of Brass and S textures with higher Schmid factor and lower equivalent sliding system number, the extruded plate possesses an yield strength not higher or even lower, but a tensile strength higher, than the cold-rolled sheet after solutionization. In addition, during the aging after pre-stretch, these textures promote T1 precipitation on preferred sliding planes of cold-rolled sheet and cause its higher yield strength and tensile strength after T8 aging.     

基于Dynaform的汽车前托架成形分析及参数优化

分析讨论了汽车前托架零件的成形工艺及有限元分析前处理中工具体与板料的网格划分;探究了摩擦系数、压边力对板料成形的影响。结果表明,较小的摩擦系数增加了零件的起皱趋势,但对破裂缺陷有较大改善;基于模面破裂危险区的形变分析,对模面修改后进一步进行压边力优化,从而进行了符合实际工艺的多阶段前托架成形优化分析。采用优化后的工艺参数和模面形状进行实际试冲,得到了合格的零件,板料变薄率和增厚率分别在20%与5%的允许范围内。实际试冲与数值模拟的板料厚度应变误差在4%范围内,且板料轮廓收料情况相符。     

树脂复合层压金属板塑性应变比r值的研究

采用实验研究为主，理论分析为辅的方法，以SPCC／Polymer／SPCC、SPCC／Polymer／L4为研究对象，研究了树脂复合层压金属板在单向拉伸时的r值的变化规律，并揭示了该变化规律对板料变形的影响。研究结果对进一步研究树脂复合层压金属板有一定参考意义。     

彩色涂层钢板时效T弯性能影响因素及规律研究

为提高彩涂板服役品质,其时效T弯性能的研究非常关键。通过对影响彩涂钢板时效T弯的主要因素,即镀锌基板表面状态、复合氧化工艺、钝化工艺进行系统研究,归纳总结了各因素对时效T弯性能的影响规律。研究结果表明:基板粗糙度R_a在1.0～1.45 μm范围内,彩板时效T弯值均满足不大于5T的技术要求,且R_a的均匀性对时效T弯性能的影响较大,R_a的相对标准偏差越小,时效T弯性能越好;基板表面峰值密度Rpc与时效T弯性能无明显相关性,时效T弯性能较好时Rpc值较小。复合氧化膜越均匀致密,膜中Co含量越高,涂层附着力越好,时效T弯值越小;钝化工艺控制Cr点数在23以上时,时效T弯(5T及以下)合格率达100%,随着Cr点数的增加,时效T弯性能明显提高。为此,提出控制基板表面粗糙度及其均匀性,控制复合氧化工艺中氧化槽碱比稳定性(碱比小于1.6),控制钝化工序Cr点数在23~25之间等措施,可提高彩板时效T弯性能。     

形变时效时间对FeMnSiCrNi合金微观组织和形状记忆效应的影响

研究了直接时效和形变时效时间对Fe-13Mn-5Si-8Cr-4Ni-0.2C合金微观组织和形状记忆效应的影响.结果表明.直接时效后只有少量Cr23C6第二相在晶界和晶内弥散析出,而形变后再时效有大量的Cr23C6在晶内沿某些特定的方向析出.形变时效时间不仅影响第二相的析出数量,还影响第二相析出的方向性,从而影响合金的形状记忆效应.形变时效时间存在最佳值.室温10%形变后再经1 073 K×300min时效,第二相数量多且在晶内析出的方向性好,合金的形状记忆效应达到最大值80%.     

2050铝锂合金薄板拉伸性能及晶间腐蚀与时效的相关性

采用拉伸性能测试、浸泡腐蚀及透射电镜(TEM)观察,研究了2050铝锂合金薄板T6及T8态时效时后的拉伸性能、晶间腐蚀(IGC)及微观组织。结果表明,T8态时效2050铝锂合金强度及伸长率均明显高于T6态时效。T6及T8态时效时,合金IGC敏感性随时效延长至峰时效阶段而逐渐降低;进一步延长至过时效阶段,IGC敏感性有所增加。另外,T8态时效时IGC敏感性明显低于T6态时效。基于提高强度、伸长率及降低IGC敏感性的综合考虑,2050铝锂合金薄板适宜的时效制度为T8态峰值时效,相应合金具有最高的强度(抗拉强度529 MPa)、良好的伸长率(10%)及最低的IGC敏感性。     

FSW对2A12铝合金时效成形的影响

为评价2A12铝合金FSW构件的时效成形工艺,研究了FSW对2A12铝合金时效成形的影响,设计了以时间为参数变量的带焊缝与不带焊缝时效成形工艺的对比试验,并进行FSW焊件与非焊件时效成形力学性能对比研究及成形性分析。结果表明,在其他条件相同的情况下,非焊接试样时效成形时,最佳回弹时效时间为10h,回弹率达25.41%;FSW焊件时效成形时,最佳回弹时效时间为8h,回弹率达33.49%。非焊接试样时效时间8h,抗拉强度达到463.4MPa;FSW试样时效时间8h时,抗拉强度达到354.1MPa。经时效成形处理的非焊接试样和FSW试样的强度均有提高,且非焊接试样的硬度明显高于焊接试样。FSW工艺对时效成形试样的回弹、力学性能及表面硬度均产生了不同程度的负面影响。     

铝合金应力／应变时效机制的第一性原理研究

基于第一性原理计算方法探讨了铝合金应力／应变时效的可能机制,综合评估了时效温度和外加应力／应变对Al-Sc合金中Al3Sc固溶边界和A1-Cu合金中Al／θ＇＇界面能的潜在影响。计算结果表明：在传统时效过程中引入外加拉应力／应变,声子态密度在高态区有红移现象,可以明显降低溶解熵;同时,导致相图中固溶线上移,表明外加拉应力／应变可降低Al3-Sc在Al-Sc合金中的极限固溶度,从而增加析出相的最大可能体积分数。外加应力／应变对Al-Cu合金中不同取向的Al／θ＇＇,界面形成能有不同程度的影响,这种差别可以通过泊松效应进一步放大,从而影响到Al-Cu合金中析出相的择优取向。这2种机制在应力／应变时效中均可能发挥重要作用。     

核反应堆用FeCrAl合金板材的试制及其组织性能研究

在对Fe13Cr5AlxNb合金熔炼、锻造、轧制等制备工艺研究的基础上,利用光学显微镜、透射电镜、扫描电镜以及电子背散射衍射研究了合金板材的微观组织演化特征。研究了不同热处理温度（800、850、900、1 000 ℃）下合金板材中第二相的析出特点及对其力学性能的影响规律。结果表明,合金板材在800 ℃保温5~25 h后,其室温力学性能稳定;合金板材在800~1 000 ℃、20 h高温时效后,在800~850 ℃时,其强度稍有降低,而在900~1 000 ℃时,其强度随温度的升高而提升。同时,对不同Nb含量的合金板材常温和高温力学性能进行了测试,Nb质量分数为1.0%~1.5%时,合金板材具有良好的力学性能。     

Investigation on deformation behavior of sheet metals in viscous pressure bulging based on ESPI

In order to analyze the effect of viscous medium on the deformation behavior of sheet metals in viscous pressure bulging (VPB), the entire deformation process including instability and fracture was investigated real-timely by the aid of electronic speckle pattern interferometry (ESPI). Images of speckle patterns were captured continuously to obtain fringe patterns representing the full field strain rate. Values of strain rates were calculated based on the fringe patterns. The evolution of the weak region from the initial defect to the groove until crack was also observed through the fringe patterns. The onset of diffuse and localized necking were determined qualitatively and quantitatively. Experimental results show that the deformation of sheet metals in VPB passed through five states, namely, uniform deformation, strain localization, diffuse necking, localized necking and fracture. A defect emerged in strain localization. The growth of the defect caused the diffuse necking and generated a groove. The groove expanded mainly in length direction until the localized necking occurred. Finally the specimen fractured as a result of groove deepening. The tangential adhesive stress provided by viscous medium in VPB restricted the locally larger strain of the specimen. The diffuse necking was postponed greatly. Theoretical prediction of the limit strains of sheet metals in VPB would be made based on the experimental results in further work.     

提高Al-Zn-Mg-Cu铝合金薄板T76状态电导率的热处理工艺研究

试验研究不同固溶温度、二级时效温度和保温时间对Al-Zn-Mg-Cu铝合金薄板力学性能及电导率的影响。结果表明,随着固溶温度提高,板材的强度提高,伸长率降低,电导率变化不大;随着二级时效温度升高,板材的强度降低,伸长率稍有降低,电导率平稳升高;随着二级时效保温时间延长,板材的强度下降,伸长率变化不大,电导率逐渐升高。该合金板材T76状态的适宜固溶温度为(467±2)℃,双级时效制度为(120±3)℃5 h+(166+3)℃36 h。     

双重时效对Ti1023合金低周疲劳行为的影响

研究了双重时效对Ti-10V-2Fe-3Al合金低周疲劳行为的影响。结果显示,高应变幅(△εt/2=1.5%,1.2%,1.0%)下,合金表现为循环软化;低应变幅(△εt/2=0.8%,0.6%)下,则表现为循环应力饱和。疲劳寿命测试结果表明,双重时效疲劳寿命和直接时效疲劳寿命相当,疲劳总应变幅和疲劳寿命满足Coffin-Manson方程。SEM断口形貌显示,双重时效后疲劳裂纹稳定扩展区有明显的疲劳条纹,疲劳裂纹以穿晶方式扩展,并伴随着撕裂棱和二次裂纹,但二次裂纹较直接时效大量减少。TEM形貌显示,不论是双重时效还是直接时效,疲劳后变形组织都很均匀。虽然双重时效和直接时效具有相当的疲劳寿命,但是这种工艺缩短了时效时间,节约了能源,能更好地满足实际工业生产需求。     

不同应力状态下St14-T冷轧薄板本构关系研究

采用液压胀形试验分析了双向拉伸变形过程板材的应力梯度和应变分布 ,确定了双向拉伸变形状态下板材的应力应变关系曲线 ,探讨了不同应力状态下板材的本构关系。研究结果表明 ,不同应力状态下板材的本构方程存在一定的差异 ,双向拉伸变形条件更有利于发挥材料塑性变形的潜力。与单向拉伸相比 ,双向拉伸变形更有助于板料变形的均匀化 ,并抑制颈缩的产生和进一步扩展     

形变时效温度对Fe-Mn-Si-Cr-Ni合金形状记忆效应的影响

研究了直接时效和形变时效温度对Fe-13Mn-5Si-8Cr-4Ni-0.2C合金形状记忆效应和微观组织的影响.结果表明,直接时效后Fe-Mn-Si-Cr-Ni合金在奥氏体晶界和晶内只有少量Cr23C6第二相弥散析出,而形变后再时效有大量的Cr23C6在奥氏体晶内沿某些特定的方向析出,显著强化基体的同时提高了ε马氏体的可逆逆转变性.形变时效温度影响第二相的析出数量和方向性,从而影响合金的形状记忆效应,存在一个最佳的时效温度.当形变后在1073 K时效300 min时,不仅第二相数量多且在晶内析出的方向性好,合金的形状记忆效应达到89%.     

不锈钢覆铝板成形极限的理论分析和实验验证

在Ｈｉｌ的各向塑性异性条件下推导了不锈钢覆铝板成形极限的计算模型。在应变比为负（β＜０）的区域,根据Ｈｉｌ的局部颈缩理论推导出了复合板的局部颈缩条件式;在应变比为正（β＜０）的区域,先根据Ｓｗｉｆｔ理论推导出了复合板的扩散颈缩条件式并计算出出现扩散颈缩的应变,然后在此基础上根据修正Ｍ－Ｋ理论推导出了复合板的局部颈缩的极限应变计算式。计算结果与实验数据吻合较好,发现复合板的成形极限介于其母材之间,并随着其母材中成形性好的材料的厚比增大而提高。     

Effects of ECAP and Aging on Mechanical and Superelastic Behaviors of Ti-Mo-Based and Ti-25at.%Nb SMAs

Ni-free Ti-based shape memory alloys (SMAs) are increasingly recognized as promising functional materials for medical applications. The mechanical properties of these metastable Ti-based SMAs are sensitive to aging and thermomechanical treatment. Effects of severe plastic deformation (SPD)-equal channel angular pressing (ECAP) and aging on superelastic behavior of Ni-free Ti-based SMAs, Ti-9.8Mo-3.9Nb-2V-3.1Al?wt.% (TMNVA) and Ti-25at.%Nb, have been investigated. The results show that the yielding strength of TMNVA alloy increases sharply with the number of ECAP processes??to greater than 1,400?MPa after two passes ECAP??but elongation of TMNVA alloy decreases severely and the plasticity is lost completely after two passes ECAP. Both ECAP process and flash annealing treatment have weak contribution to the superelastic recoverable strains of Ti-Mo-based alloy. For Ti-25at.%Nb alloy, after one pass ECAP process at 400?°C, the yielding stress increases obviously, and the recovery strain increases a little. With the further increase in the number of ECAP processes, the yielding stress and the recovery strain change little. Aging treatment at low temperature after ECAP process is in favor of superelasticity of Ti-25at.%Nb alloy. An almost completely recoverable strain of 1.5% is obtained in Ti-25at.%Nb alloy after two passes ECAP and aging at 300?°C for 1?h. The mechanisms of the effects of SPD and aging are also discussed.     

Strain Aging of X100 Steel in Service and the Enhanced Susceptibility of Pipelines to Stress Corrosion Cracking

In this study, experimental tests were performed to investigate the strain aging behavior of X100 pipeline steel in service and the resulting enhancement of susceptibility of pipelines to stress corrosion cracking (SCC). Results demonstrated that an immediate rise in temperature during coating application could result in strain aging of X100 steel, as indicated by increasing strength and decreasing elongation as well as the presence of Lüders strain during yielding. The aged steel is associated with an enhanced cracking susceptibility under cathodic protection potentials. It is believed that strain aging is able to enhance hydrogen evolution and the further permeation into steel, resulting in hydrogen-induced SCC of the steel.