挤压态镁合金板材复合变形过程中的孪晶组织演变规律

采用扫描电镜(SEM)研究了挤压态镁合金压痕-压平复合变形过程中动态再结晶及孪晶组织演变规律。结果表明:在镁合金压痕-压平复合变形过程中,随着复合变形系数和变形温度的增加,AZ31镁合金的孪晶数量逐渐增多,动态再结晶程度增大,晶粒细化效果明显。动态再结晶的主要形核之处是原始晶粒的晶界处,动态再结晶新晶粒产生于原始晶粒的晶界处,且形状为典型的项链状结构,孪晶界也是动态再结晶的有利形核位置。在压痕-压平复合变形过程中,较低的变形温度和较大的变形程度有利于孪晶组织的形成,且孪晶组织容易出现在大晶粒内部。

基于元胞自动机的AZ31镁合金复合变形动态再结晶组织演变规律

提出了一种压痕-压平复合变形方法,分析了复合变形基本特征及作用,定义了复合变形程度表征参数,即复合变形压下量、波形间距和复合变形系数。将计算机模拟软件及元胞自动机方法相结合,对AZ31镁合金压痕-压平复合变形过程中的动态再结晶组织演变规律进行数值模拟研究。结果表明,压痕-压平复合变形方法可以有效细化AZ31镁合金的晶粒尺寸,改善组织性能。AZ31镁合金复合变形过程中,随着变形温度的升高、复合变形系数的增加以及复合变形压下量的增大,晶粒尺寸显著降低。数值模拟结果与实验结果相吻合,相对误差小于13.8%。

树脂结合剂金刚石双绞合线锯丝绞合变形分析及参数确定

固结磨粒金刚石双绞合线锯丝可解决大尺寸晶体材料切割排屑困难、加工液流入不畅等问题。通过对树脂结合剂固结磨粒金刚石线锯丝的双绞合绞制变形分析发现,采用退扭绞合工艺可有效降低双绞合线锯丝的应力,计算并确定了绞合线锯丝螺旋升角的取值范围(81°<α≤85°)。针对304钢、65Mn、SWPB三种基体材料,得到了绞制所需的张紧力、节距值的范围。研究结果为双绞合线锯丝的制造技术提供了参考数据。

某发动机弹性密封贴合面轴向变形量计算

为准确、定量评估某发动机弹性密封件贴合面的轴向变形,首先建立贴合组件的模型,随后对模型中的各零部件赋予导热系数与材料,施加初始温度、换热系数等边界条件,计算出四种恶劣工况下精确的温度场分布,随后将温度场分布作为输入条件导入结构求解的模型中求解,输入材料的热膨胀系数和弹性模量,施加轴向力载荷时考虑2g的正反方向的过载,分别求出极限情况下的两个大的组件中端面的轴向变形,最后进行求差,得到最大的轴向相对变形量,从而为进一步评估压缩量对弹性密封的影响提供了科学的定量依据。

变形镁合金疲劳性能的研究进展

总结了近年来变形镁合金疲劳性能的最新研究进展,指出夹杂、孔洞和刀痕促进变形镁合金疲劳裂纹的萌生,采用合适的整体(包括合金化、形变强化和热处理)和表面(包括喷丸、滚压和涂层)改性技术是改善变形镁合金疲劳性能的重要途径。此外,加载频率、腐蚀性介质类型及pH值等对变形镁合金的疲劳性能也有重要影响。最后,根据变形镁合金疲劳性能的研究现状指出了今后的研究方向。

某钢结构栈桥变形异常问题分析

针对某既有工业类钢结构栈桥项目的变形,根据现场观察、调查了解、现场检测、结构体系分析,推测出产生该变形的原因后,在不增加额外荷载和约束的前提下,通过计算模型的分步施工来实现对现状变形的拟合,进而可以对构件的承载力、整体结构的安全性作出更真实有效的分析,该方法对于既有建筑的变形分析是一种比较实用的方法。

浅谈冲压件对压合工艺的影响

介绍了4门两盖冲压件的质量状态与要求,阐述冲压件对压合工艺的影响,分析并解决4门两盖、翼子板等包边件的变形缺陷,从而提高整车美容质量。

Strengthening mechanism of T8-aged Al-Cu-Li alloy with increased pre-deformation

The microstructure evolution and mechanical properties of a T8-aged Al-Cu-Li alloy with increased pre-deformation(0-15%) were investigated,revealing the microstructure-strength relationship and the intrinsic strengthening mechanism.The results show that increasing the pre-deformation levels remarkably improves the strength of the alloy but deteriorates its ductility.Dislocations introduced by pre-deformation effectively suppress the formation of Guinier-Preston(GP) zones and provide more nucleation sites for T1 precipitates.This leads to more intensive and finer T1 precipitates in the samples with higher pre-deformation levels.Simultaneously,the enhanced precipitation of T1 precipitates and inhibited formation of GP zones cause the decreases in number and sizes of θ′ precipitates.The quantitative descriptions of the strength contributions from different strengthening mechanisms reveal that strengthening contributions from T1 and θ′ precipitates decrease with increasing pre-deformation.The reduced diameters of T1 precipitates are primarily responsible for their weakened strengthening effects.Therefore,the improved strength of the T8-aged Al-Cu-Li alloy is mainly attributed to the stronger strain hardening from the increased pre-deformation levels.

Effect of annealing temperature on microstructure and mechanical properties of Mg-Zn-Zr-Nd alloy with large final rolling deformation

In this study,the Mg-3Zn-0.5Zr-χNd(χ=0,0.6)alloys were subjected to final rolling treatment with large deformation of 50%.The impact of annealing temperatures on the microstructure and mechanical properties was investigated.The rolled Mg-3Zn-0.5Zr-0.6Nd alloy exhibited an ultimate tensile strength of 386 MPa,a yield strength of 361 MPa,and an elongation of 7.1%.Annealing at different temperatures resulted in reduced strength and obviously increased elongation for both alloys.Optimal mechanical properties for the Mg-3Zn-0.5Zr-0.6Nd alloy were achieved after annealing at 200℃,with an ultimate tensile strength of 287 MPa,a yield strength of 235 MPa,and an elongation of 26.1%.The numerous deformed microstructures,twins,and precipitated phases in the rolled alloy could impede the deformation at room temperature and increase the work hardening rate.After annealing,a decrease in the work hardening effect and an increase in the dynamic recovery effect were obtained due to the formation of fine equiaxed grains,and the increased volume fraction of precipitated phases,which significantly improved the elongation of the alloy.Additionally,the addition of Nd element could enhance the annealing recrystallization rate,reduce the Schmid factor difference between basal and prismatic slip systems,facilitate multi-system slip initiation and improve the alloy plasticity.

主动主反射面天线促动器调整量计算与误差分析

主动主反射面天线通过调整安装在面板下方的促动器来提高表面精度,现有的促动器调整量计算方法多数忽略了面板弹性变形对调整精度的影响。文中通过力学仿真模拟来表征促动器调整过程对面板自身弹性变形的影响。首先,构建单块反射面面板变形拟合模型,并对拟合模型的权重进行优化,进而推导出整个反射面的变形拟合模型;其次,考虑到实际工程中相邻面板共用促动器,因此对促动器编号进行归并,进而推导出相邻面板共用促动器时促动器最佳调整量的计算模型。为了验证面板变形拟合模型的计算精度,分别从拟合模型的变形表征能力和促动器调整量的计算精度两个方面开展仿真验证工作,并从促动器调整误差和促动器故障两个方面分析促动器调整误差对反射面调整精度的影响,为工程中评估促动器调整精度提供参考。

变形画与联想

儿童联想变形画系列稿之二变形画与联想□王守公变形画的功用不仅在于学习一种有趣的绘画形式，练习基本的绘画能力，而且在相当大的程度上更在于由此种非同寻常的绘画方式培养儿童的联想与想象的能力及其创造力。联想是创造才能的构成因素之一，联想是想象的开始，联想与...

A new rhombohedral phase and its 48 variants inβtitanium alloy

A new rhombohedral phase(termed R′)in a solution-aging-treated titanium alloy(Ti-4.5Al-6.5Mo-2Cr-2Nb-1V-1Sn-1Zr,wt.%)was identified.Its accurate Bravais lattice parameters were determined by a novel unit cell reconstruction method based on conventional selected-area electron diffraction(SAED)technique.The orientation relationship between R'phase and BCC phase was revealed.The results show that the R′phase is found to have 48crystallographically equivalent variants,resulting in rather complicated SAED patterns with high-order reflections.A series of in-situ SAED patterns were taken along both low-and high-index zone axes,and all weak and strong reflections arising from the 48 variants were properly explained and directly assigned with self-consistent Miller indices,confirming the presence of the rhombohedral phase.Additionally,some criteria were also proposed for evaluating the indexed results,which together with the Bravais lattice reconstruction method shed light on the microstructure characterization of even unknown phases in other alloys.

Microstructural evolution and deformation mechanisms of superplastic aluminium alloys:A review

Aluminium alloy is one of the earliest and most widely used superplastic materials.The objective of this work is to review the scientific advances in superplastic Al alloys.Particularly,the emphasis is placed on the microstructural evolution and deformation mechanisms of Al alloys during superplastic deformation.The evolution of grain structure,texture,secondary phase,and cavities during superplastic flow in typical superplastic Al alloys is discussed in detail.The quantitative evaluation of different deformation mechanisms based on the focus ion beam(FIB)-assisted surface study provides new insights into the superplasticity of Al alloys.The main features,such as grain boundary sliding,intragranular dislocation slip,and diffusion creep can be observed intuitively and analyzed quantitatively.This study provides some reference for the research of superplastic deformation mechanism and the development of superplastic Al alloys.

Effect of cold rolling deformation on microstructure evolution and mechanical properties of spray formed Al−Zn−Mg−Cu−Cr alloys

The impact of cold rolling deformation,which was introduced after solid solution and before aging treatment,on microstructure evolution and mechanical properties of the as-extruded spray formed Al−9.8Zn−2.3Mg−1.73Cu−0.13Cr(wt.%)alloy,was investigated.SEM,TEM,and EBSD were used to analyze the microstructures,and tensile tests were conducted to assess mechanical properties.The results indicate that the D1-T6 sample,subjected to 25%cold rolling deformation,exhibits finer grains(3.35μm)compared to the D0-T6 sample(grain size of 4.23μm)without cold rolling.Cold rolling refines the grains that grow in solution treatment.Due to the combined effects of finer and more dispersed precipitates,higher dislocation density and smaller grains,the yield strength and ultimate tensile strength of the D1-T6 sample can reach 663 and 737 MPa,respectively.In comparison to the as-extruded and D0-T6 samples,the yield strength of the D1-T6 sample increases by 415 and 92 MPa,respectively.

基于国密技术的地理信息数据安全应用方法初探

随着智慧城市建设的推进与城市精准管理需求的不断提升,各部门的精准化、智能化的高效管理需求对地理信息数据提出了越来越高的要求。然而,当前地理信息服务模式在以下方面存在不足:一是部门需要更快速高效的地理信息数据更新服务;二是各部门精准管理需求越来越高,而当前空间位置精度(非线性脱敏处理后)无法满足应用需求。因此,通过本文的研究,是期望通过解决敏感数据的授权使用问题和安全保障,从而推动地理信息数据获取处理全面提速,提高综合服务能力。

高强高性能混凝土的体积稳定性

本文阐述了高性能混凝土体积稳定性的各种类型及其各自影响因素 ,介绍了目前国内外在这方面的研究进展和方法。在此基础上提出了应从综合的角度把混凝土的所有体积变形合成为一种“合变形” ,并在接近实际使用条件范围内建立模型 。

Flow softening behavior and microstructure evolution of Al-5Zn-2Mg aluminum alloy during dynamic recovery

The flow stress behavior and microstructure development of Al-5Zn-2Mg （7005） aluminum alloy were studied by hot compression tests at deformation temperatures between 300-500 ＆#176;C and strain rates between 0.05-50 s-1. The deformed structures of the samples were observed by optical microscopy （OM）, transmission electron microscopy （TEM） and electron backscattering diffraction （EBSD） analysis. The calculated activation energy is 147 kJ/mol, which is very close to the activation energy for lattice self-diffusion in aluminum （142 kJ/mol）. Dynamic recovery is the dominant restoration mechanism during the deformation. At high strain rate of 50 s-1, temperature rise due to deformation heating leads to a significant flow softening. Microstructure observations indicated that the remaining softening after deformation heating correction at high strain rate and the softening observed at high temperature are associated with grain coarsening induced by grain boundary migration during dynamic recovery process.

Hot deformation behavior of extruded AZ80 magnesium alloy

The hot deformation behavior of extruded AZ80 magnesium alloy was studied through hot compression tests performed at temperatures ranging from 250 to 450 ~C with strain rates varying from 0.001 to 10 s-1. The flow stress was corrected due to the deformation heating. The Zener-Hollomon parameter （Z parameter） and processing map were established to describe the hot deformation behavior. The results indicate that the applicable deformation should be conducted at the strain rate of 0.1 s-~ and the temperature range of 350-400 ~C. Besides, the relationship between the microstructure evolution and Z parameter was also discussed. High temperature and low strain rate result in a low Z parameter, which leads to full dynamic recrystallization （DRX） and large DRX grain size in the microstructure. Considering processing map and microstructure, the hot deformation should be carried out at the temperature of 400 ~C and the strain rate of 0.1 s 1.

Deformation mechanism and softening effect of extruded AZ31 magnesium alloy sheet at moderate temperatures

The flow stress behavior of extruded AZ31 magnesium alloy sheet was investigated by means of compression tests at temperatures between 473 and 523 K and strain rates ranging from 0.001 to 1.0 s-1. The deformation activation energy of the sheet in extrusion direction （ED） was calculated, and the relationship between the softening effect and deformation mechanism was elucidated by optical microscopy and transmission electron microscopy. The results show that when the extruded AZ31 magnesium alloy samples were compressed at moderate temperatures in ED direction, the deformation activation energy is 174.18 kJ/mol, which means that dynamic recrystallization （DRX） is the main softening effect and is controlled by cross slip of thermal active dislocation. Dislocation slip is the main deformation mechanism in moderate-temperature deformation process except twinning. The main DRX effect at moderate temperatures can be considered to be continuous dynamic recrystallization accommodated with twinning DRX.

Effect of deformation temperature on microstructure and mechanical properties of 7055 aluminum alloy after heat treatment

The multi-pass hot compression test of 7055 aluminum alloy was performed at different temperatures and then the samples were heat treated by T6 heat treatment.The compressed samples were analyzed by OM and TEM.The results reveal that the average aspect ratio of the grains in the specimens compressed first decreases and then increases,the dislocation density decreases and subgrain diameter increases with the increase of deformation temperature.The effects of deformation temperature on the microstructure and mechanical properties of 7055 aluminum alloy after heat treatment were investigated by means of OM and mechanical property test.The results indicate that the deformation temperature significantly influences microstructure and mechanical property of 7055 aluminum alloy.The volume fraction of recrystallization grains presents a ＂fall-rise＂ pattern with the deformation temperature rising.The mechanical properties get better when the volume fraction of recrystallization grains decreases.Moreover,the volume fraction of recrystallization grain has a minimum value,appropriately 45%,and the sample exhibits the highest strength and elongation at the deformation temperature of 400 ℃.