基于数字孪生的热处理智能化技术研究进展

为减少热处理智能化技术数据孤岛的状态,数字孪生的运用被广泛关注。数字孪生技术是智能化制造领域的先进智能技术,也是解决数据孤岛的重要方法之一。本文介绍了数字孪生技术与基于数字孪生的热处理研究现状。以车间数字孪生框架为基础,从物理车间、虚拟车间、车间服务系统、孪生数据4个方面介绍数字孪生的研究现状,分析了各部分中存在的主要问题。针对基于数字孪生为基础的热处理技术,结合传统热处理技术与特殊热处理的智能化研究进展,分析数字孪生技术在热处理中的应用与进展。

铸态EV31A合金中稀土元素的分布及对显微组织和力学性能的影响

利用光学显微镜(Optical microscope,OM)、X射线衍射仪(X-ray diffractometer,XRD)、扫描电子显微镜(Scanning electron microscope,SEM)、能谱分析仪(Energy dispersive spectrometer,EDS)、透射电镜(Transmission electron microscope,TEM)和电子万能试验机等手段对传统砂型重力铸造方法制备的EV31A合金的显微组织和性能进行了深入研究。实验结果表明:铸态EV31A合金的显微组织由α-Mg和α-Mg+Mg_(41)(Nd_(0.9)Gd_(0.1))_(5)共晶相组成,由于稀土元素含量较少,共晶反应发生在α-Mg结晶后期,表现为除少量固溶于α-Mg基体中,含稀土元素的Mg_(41)(Nd_(0.9)Gd_(0.1))_(5)相主要分布在α-Mg的晶界处。Mg_(41)(Nd_(0.9)Gd_(0.1))_(5)相为bcc结构,晶格常数为0.285 nm,呈鱼骨状,尺寸在数十微米。合金中α-Mg基体的晶粒尺寸为56.8μm。EV31A铸态合金的抗拉强度、屈服强度和延伸率分别为207 MPa、124 MPa和7.0%。合金具有优异力学性能主要归因于Zr元素所带来的细晶强化,Gd、Nd、Zr等溶质原子的固溶强化,共晶Mg_(41)(Nd_(0.9),Gd_(0.1))_(5)相所带来的第二相强化等多种强化方式的协同作用。

不锈钢波纹膜片激光焊接的组织和性能研究

对SUS304奥氏体不锈钢波纹膜片进行激光焊接工艺试验,基于Minitab软件,分析工艺试验结果,筛选最佳工艺参数。结果表明:基值功率120 W、峰值功率500 W、离焦量+4 mm、焊接速度1050 mm∕min时,可获得成形良好的焊缝。接头显微组织表明:焊接热影响区较窄,主要为轧制状的奥氏体组织,但其组织相比母材区有所增大;焊缝中心区主要为细的等轴晶粒,边缘处主要为垂直于熔合线的柱状晶粒。力学性能测试结果表明:接头断裂于热影响区,其最大抗拉强度为493 MPa,达到母材抗拉强度的82%;接头主要呈现韧窝断裂特征,断口同时存在等轴和剪切韧窝。

AlFeMn合金冷轧过程中显微硬度与织构研究

采用硬度测试仪、透射电镜(Transmission electron microscopy,TEM)、X射线衍射仪(X-ray diffraction,XRD)等手段研究了冷轧过程中AlFeMn合金板材的硬度、微观组织、织构变化。AlFeMn合金的显微硬度先随冷轧率增加而增加,在冷轧率为82%时,硬度达到峰值;然后硬度随冷轧率增加而下降。与此同时,合金中的位错密度明显降低,出现多边化亚晶。结果表明,冷轧过程中,AlFeMn合金存在由加工硬化转变为加工软化的行为。加工软化在中低应变量(≤78%冷轧率)时,copper、S取向含量随冷轧率增加略有增加,而brass取向含量基本保持不变;在达到82%冷轧率时,copper、S、brass取向含量明显急剧增加,在冷轧率超过84%后含量又急剧降低。Cube取向含量在加工硬化期间一直降低,在加工软化后期含量略有增加。结果表明,加工软化的发生伴随有晶粒取向的变化。

钴/镍复合中间层真空扩散连接钨与钢

以钴粉/镍箔为复合中间层,采用800,900和1 000℃等三种连接温度,加压10 MPa并保温120 min的工艺条件,对钨/钢真空扩散连接.研究了接头的微观组织、成分分布、力学性能及断口特征.结果表明,连接温度为800℃和900℃时,钨/中间层界面金属间化合物生成很少,对应接头抗剪强度分别为186 MPa和172 MPa,断口均位于钨母材中近界面的位置,为典型解理断裂形貌;当连接温度升至1 000℃时,钨/中间层界面生成厚度小于2μm的连续金属间化合物层,接头抗剪强度降至115 MPa,断裂也发生在钨母材中近界面的位置,断口大部分区域为沿晶断裂特征.

核聚变堆钨/钢复合结构连接的研究现状

核聚变堆中的面向等离子体材料钨需要和结构材料低活化钢形成高质量连接,以制造出可满足极端苛刻工作条件的钨/钢复合结构件。介绍了钨/钢复合结构连接的难点,详细阐述了钨/钢复合结构的连接技术、连接接头的热应力与降应力方法以及力学性能等方面的国内外研究现状。指出对钨/钢复合结构导热性、抗热疲劳性及高温与强辐射环境下工作的可靠性要进行系统测试与分析,并以此为基础不断改进连接技术与工艺,标准化测试方法,确定钨/钢复合结构关键性能的优先顺序及指标等是今后核聚变堆钨/钢复合结构连接研究的发展方向。

Study on Microstructure and Properties of TIG Welded Joint of TC2 Titanium Alloy and Quality Inspection

TIG welding experiments of TC2 titanium alloy sheet was carried out,and the well-formed weld was obtained.After welding process,the cross-section microstructure,mechanical properties,fracture morphology and quality inspection of the joint were studied.The results show that the microstructure of the weld consists of a large number of acicularα′andβblock.The microhardness curve shows that the microhardness value in the fusion zone(FZ)of the joint is significantly higher than that in the heat affected zone(HAZ)and the base metal(BM),and the microhardness of the base metal is the lowest.The tensile strength of the joint is equivalent to that of the base metal,and the fracture morphology shows that the fracture mechanism of the joint is mixed ductile-brittle fracture mode.The weld quality is excellent through chemical inspection,penetrant inspection and X-ray inspection.

Structural and Magnetic Properties in Nd_(0.7)Sr_(0.3)MnO_3 Manganite

The temperature evolution of the crystal structure for Nd_(0.5)Sr_(0.5)MnO_3 has been investigated by powder XRD between 125 Kand 725K.The structure can be described with a monoclinic symmetry(space group P21/m)in the temperature range of 125—175 K,while with the increase in temperature between 175 Kand 575 Kthe structure involves a higher orthorhombic symmetry(space group Imma).The rhombohedral structure with space group R-3cis observed at high temperature region of 575—725K.The increase in the magnetization at low temperatures can be ascribed to the field-induced short-range magnetic order of the Nd3+ions.The dc and ac susceptibility data show some anomalies around the FM-PM transition region which can be attributed to the glass behavior and magnetic relaxation.

Achieving High-Quality Aluminium Alloy Welded Joint with Fine Grains Using Submerged Friction Stir Welding

The purpose of this study is to reveal the microstructure and mechanical properties of friction stir welding(FSW)joints prepared in water/air.For comparable analysis,the submerged FSW(SFSW)and conventional FSW are both conducted on 6061-T6 aluminum alloy plates at the combination rotation speed of 800 r/min and the traverse rate of 50 mm/min.The results show that a greatest grain refinement is achieved by SFSW,which is remarkably smaller than that of the base material(BM)and air FSW(AFSW)samples,leading to a significant improvement of tensile strength from 202.5 MPa in the AFSW sample to 232 MPa in the SFSW sample.

Microstructure and Mechanical Properties of Ti-4Al-1.5Mn Resistance Spot Welding Joints

Ti-4Al-1.5Mn dual phase titanium alloy sheet was spot welded by pneumatic resistance spot welder.The effects of different welding parameters on shear load and nugget diameter were studied.The results show that the maximum shear load of solder joint increases first and then decreases with the increase of electrode pressure and welding current,while the nugget diameter increases with the increase of electrode pressure and welding current.Electrode pressure of 0.20 MPa and welding current of 46 A are the optimal process parameters,under which the maximum shear load of solder joint reaches 8.80 kN.The microstructure of nugget zone is coarse acicular martensite,and the solder joints fail in a mixed mode of intergranular brittle-ductile fracture.

Preparation and Microwave Absorption Property of Sr_2FeMoO_6 Powder

Double perovskite oxide Sr_2FeMoO_6 powder is prepared by a solid state reaction method.The microwave absorption properties of Sr_2FeMoO_6 and paraffin wax composites are studied in the frequency range of 2—18GHz at room temperature.The optimum absorption-36.7dB is achieved at 17.7GHz with a matching thickness of 5.0mm,which indicates that Sr_2FeMoO_6/paraffin composites can be potential microwave absorbers in a relatively high frequency range.The excellent microwave absorption properties are attributed to the good electromagnetic match between dielectric loss and magnetic loss.The dielectric loss is considered to be caused by orientation polarization and interfacial polarization,while the magnetic loss is caused by natural resonance in the low frequency range,eddy current loss as well as exchange resonance in the high frequency range.

2024铝合金填丝TIG焊接头搅拌摩擦加工组织和性能研究

熔化焊方法在铝合金连接方面发挥着重要作用,但所产生的焊缝存在一些冶金问题。因此,针对铝合金熔化焊焊缝开发具有较高加工柔性裕度的有效改性/修复工艺尤为迫切,这对提高接头服役性能、延长服役寿命具有重要工程意义。通过对使用ER4043焊丝典型AA2024铝合金TIG焊接头焊缝进行搅拌摩擦加工(Frictionstir processing,FSP),研究了FSP对熔焊缝微观结构和性能的影响规律。结果表明,TIG焊接头焊缝由粗大铸态树枝晶、Al-Si共晶网和冶金缺陷组成;经FSP处理后,焊缝铸态组织被完全消除,转变为致密、均匀、细晶的Si颗粒增强复相组织,导致TIG焊接头强塑性和耐蚀性同步提升。建立了FSP前后TIG焊接头微观结构演变与性能改善之间的构效关系,揭示了TIG焊接头FSP后性能提高的微观结构根源,为其他合金体系熔焊接头改性/修复提高性能提供新的思路和方法。