Microhardness and Microstructure Studies on Laser Surface Alloyed Aluminum Alloy with Ni-Cr

Aluminum alloy LM13 was surface alloyed with Ni and Cr of different compositions (in wt.%) at various laser powers (1 kW, 1.5 kW, and 2 kW) using CW CO₂ laser. Microhardness and microstructure of alloyed regions were examined.

The study shows that surface alloying is achieved when the laser power is sufficiently high (1.5 kW). Microhardness increases appreciably when the Cr concentration is increased in the Ni-Cr composition. However, in the alloyed region, large variations in microhardness are observed with depth below the surface of the material. Microstructure exhibits needle structure when Ni-concentration is high and undergoes a phase transformation when Cr-concentration is increased. XRD analysis in the alloyed samples shows formation of intermetallic compounds.     

AZ91D镁合金激光熔凝层的缺陷

以AZ91D镁合金为研究对象,研究激光熔凝镁合金的工艺特点,分析熔凝层中出现的常见缺陷,并探讨其产生的主要原因.结果表明:气孔、裂纹和夹杂是AZ91D镁合金激光熔凝层中存在的主要缺陷.但只要熔凝过程中工艺参数选择合适,这些缺陷是可以避免或减少的.     

激光微织构与自组装对铝合金表面润湿性的影响

利用激光加工在铝合金表面进行微织构,通过自组装工艺在微织构表面修饰有机硅烷分子膜,制备得到具有疏水/超疏水性表面。利用扫描电镜、三维形貌仪、接触角测量仪对微织构表面微观形貌和润湿性进行表征。结果表明:激光微织构具有的微米级粗糙结构与自组装分子膜的共同作用对超疏水表面的构建具有重要作用;接触角随激光微织构加工间距(50~100μm)的减小而增大,且与微织构的形貌类型相关。漂浮承载实验表明,超疏水表面符合Cassie-Baxter状态模型,且可有效提高平台的漂浮承载能力。     

Machinability of 7116 Structural Aluminum Alloy

The aim of the present work is to study the effect of heat treatment conditions on the surface roughness of 7116 structural aluminum alloy. The specimens were prepared by casting to attain the required chemical composition, and then hot extruded to form bars. The extruded bars were then subjected to the different proposed heat treatment cycles, namely, annealed, naturally aged, artificially aged, and artificially aged with superimposed free forging and the as-received condition. The specimens were then turned at different cutting conditions—velocities, feeds, and depth of cuts—using high speed tools (HSS). The surface roughness values were then assessed. Based on the results obtained, the artificially aged condition with superimposed effect of cold forging shows the best machinability (presented by the measured surface roughness) as a result of the increase in hardness. Hardness has a pronounced effect on the formation of built-up edge (BUE) for the material under investigation.     

铝合金微弧氧化陶瓷层的磨损特性

研究了微弧氧化陶瓷层粗糙度对磨损特性的影响及在不同溶液添加剂中生成的铝合金微弧氧化陶瓷层的磨损特性,并与镀硬铬及耐磨磷钒铜铸铁的磨损特性进行了对比.试验结果表明:随着微弧氧化陶瓷层粗糙度的增大,其初期磨损量较大,当磨损一定时间后,其磨损失重量接近于零;溶液添加剂对陶瓷层的磨损特性没有明显的影响;微弧氧化陶瓷层的磨损特性明显优于镀硬铬及磷钒铜耐磨铸铁.     

Efficiency of Protection Methods Against Corrosion-Fatigue Damage of D16T Aluminum Alloy

Strength of Materials - The results of corrosion-fatigue studies on the D16T aluminum alloy after its protection by different methods are presented. The effects of cathodic polarization,...     

铝锌合金在镁合金AZ91D中的扩渗机理及腐蚀性能研究

采用包埋铝和锌的方法在镁合金AZ91D表面制备了铝-锌合金化涂层,并且利用x射线衍射、能谱分析研究了该涂层的组织和耐腐蚀性能。该涂层外层为AlMg2Zn, Mg7Zn3 和Mg17Al12 金属间化合物层;内层为Mg17Al12金属间化合物分布于α-Mg晶界。研究表明,与镁合金基体相比较在质量分数为3.5wt.% NaCl扩渗层显示出较好的耐腐蚀性能。盐雾腐蚀说明,Al-Mg-Zn合金化扩渗层对于降低腐蚀速率起到有效作用。此外,合金化扩渗层与基体的结合是冶金结合,且涂层的显微硬度显著提高。     

Laser Refining of a Surface Layer with Silicon Carbide

The article discusses the effect of adding silicon carbide by laser remelting of low-carbon steel. Tests in laser remelting were carried out with energy inputs ranging between 10 and 80 J/mm² with the most favorable degree, i.e., 30%, of overlapping of individual trace. Sufficient energy input was necessary to dissolve silicon-carbide with iron. A microchemical analysis of the remelted layer confirmed the dissolution of silicon carbide and formation of a smaller portion of martensite (10-20%) and of suesite Fe₃Si (65-80%). It was found that the test-specimen deformation was smallest with the laser-beam in the zig-zag motion. The surface was also assessed visually. The choice of adequate remelting conditions reduced, i.e., prevented, the occurrence of cracks and other defects. The influence of energy input and the mode of laser-beam travel on the efficiency of remelting, i.e., refining, was described by a ratio of the width of the remelted surface layer to its depth, which should amount to around 5:1.     

Fatigue Life Enhancement of a D16at Aluminum Alloy for Aircraft Components with Fastener Holes

Strength of Materials - D16AT aircraft Al-alloy was evaluated. The friction stir hole expansion (FSHE), solid mandrel cold working and symmetric cold expansion (SCE) methods were compared. The...     

镁合金激光表面改性研究进展

综述了激光表面改性（激光表面重熔、激光表面合金化、激光表面熔敷、激光多层熔数）的研究与应用,最后提出了存在的问题和努力的方向。     

航空用铝合金表面处理的研究现状与展望

全面介绍了国内外铝合金在建筑、汽车、航空航天等行业的应用及研究进展.主要阐述了航空航天领域结构胶接在国内外的发展状况、胶接用铝合金表面处理方法的目的、表面处理的机理及分类、影响表面处理质量的工艺参数、现代表面分析技术等.并对近年来国内外应用最广、技术最成熟的磷酸阳极化表面处理技术的应用及优缺点进行了分析,并展望了该领域研究的发展趋势.     

Experimental Study on the Surface Property Changes of Aluminum Alloy and Stainless Steel after Impingement with Submerged Cavitation Jet

Strength of Materials - With the development of green manufacturing technology, high-pressure cavitation water jet cleaning and shot peening technologies are gradually replacing traditional...     

铝合金激光表面改性技术研究进展

阐述了国内外铝合金激光表面改性技术的最新研究进展,重点介绍了激光表面重熔(LSM)、激光熔覆(LC)及激光表面合金化(LSA)3种表面激光改性方法和其对铝合金表面组织的影响及改性效果,总结了铝合金表面激光改性过程中存在的问题,并指出了今后努力的方向.     

响应面法分析7075铝合金激光焊接参数对焊接质量的影响规律

本工作选取激光焊接头的外观成形质量作为评价指标,采用响应面法分析焊接参数对焊接质量的影响规律.选用3 mm厚7075铝合金板材进行光纤激光焊接,测量熔深、熔宽和焊缝成形面积,计算焊缝成形系数.借助响应面分析方法将试验数据进行模拟、建模和比对,选择最佳数学模型建立回归模型,得到焊缝成形系数和焊缝截面积的三维响应面曲线.通过模拟预测,发现焊接功率、焊接速度对焊缝成形系数和焊缝截面积的影响较大,离焦量对焊缝成形系数的影响较大.研究结果表明,焊缝成形系数和焊缝截面积的实测值与预测值较为接近,焊缝成形系数预测值比实测值高0.61％,焊缝截面积预测值比实测值高1.9％,模型拟合度较好,得到较优的焊接参数为:焊接功率为2300 W,焊接速度为45 mm·s-1,离焦量为1,保护气体流量为15 L/min.在该参数下的焊缝成形系数为0.803,焊缝截面积为4.436 mm2,焊缝的抗拉强度为325 MPa.     

Temperature Criterion of Laser Welding for Joining Aluminum Alloy with Low-Carbon Steel

Aluminum alloy and low-carbon steel are dissimilar metals. In order to obtain a reciprocal comprehensive property in a joint component of aluminum alloy and low-carbon steel, laser welding was used as a novel joining process. Based on the experimental results, the temperature criterion of laser welding for joining of aluminum alloy and low-carbon steel is discussed in this paper.     

镁合金磷化工艺及磷化膜性能的研究

为了有效提高镁合金表面涂层的防护能力,研制了特定的配方体系对AZ31D镁合金基体进行磷化处理,并进行涂装和性能检测试验.结果表明,该配方体系能制备出表观均匀、细致的磷化膜,金相显示其晶粒均匀.该磷化膜与有机涂层的结合力牢固,用划格法测定膜与环氧涂层甚至与丙烯酸涂层的附着力均能达到1级,而没有磷化膜的金属基体与丙烯酸涂层的附着力仅能达到2级.通过48 h中性盐雾试验表明,有磷化膜的涂层比没有磷化膜的涂层的耐腐蚀性能有所提高.     

多孔铝合金的铸造工艺研究

采用加压铸造工艺，制备出了多孔铝合金。系统地研究了预制块的制备工艺过程及影响因素。利用所制备的预制块，研究了多孔铝合金的加压铸造工艺。研究表明，预制块孔隙大小及其初始温度、金属液浇注温度、外加压力等影响了金属液在预制块中的充型长度。采用合理的工艺，就可以获得大尺寸的多孔制品。     

6A16铝合金车身表面TiC/MAO涂层的组织及耐蚀性能分析

为了提高6A16铝合金的耐蚀能力,实现对微弧氧化涂层微观组织结构与成分的精确调控,采用微弧氧化技术及水热法在6A16铝合金表面制得TiC/MAO复合涂层,并通过试验测试方法对制备参数进行优化,获得了水热法制备复合膜的最优参数为:溶液pH值8,反应时间24 h,反应温度180℃.当pH=8时形成了致密的TiC膜,试样达到...     

铝合金表面铈基转化膜研究进展

铝合金具有成本低、强度质量比高、可加工性能良好等优点,被广泛应用于航空、交通、建筑等领域.但铝合金表面易发生小孔腐蚀和晶间腐蚀,需要进行防腐处理才能满足应用要求.稀土元素铈因具有特有的电子层结构和物理化学特性,是制备铝合金稀土转化膜最具优越性的元素,以此为防腐基材开发的稀土转化膜技术被认为是最有可能替代铬酸盐钝化的技术.目前所报道的铈基转化膜工艺有化学浸泡法、溶胶-凝胶法、电化学法、磁控溅射法等.其中,化学浸泡法制备过程简单,但铈离子的转化和沉积速率较难控制一致,膜层微米级裂纹较多;溶胶-凝胶法制备的膜层与基体结合强度高,耐蚀性好,但需要大量铈盐,且产生较多废酸、碱液,成本高,环境污染大;电化学法在低温下实现性能可控的铈基转化膜,成本低,但成膜有大量晶间裂纹,结构疏松,成膜质量差;磁控溅射法制备的涂层均匀,成分可控,但靶材的利用率低,难以实现强磁性材料的低温高速溅射.总体来看,目前所报道的铈基转化膜工艺存在溶液体系稳定性差,所制备的转化膜层不稳定、容易开裂,以及制备成本较高的问题,难以满足工业化应用的要求.铈基转化膜成膜机理被普遍认为是阴极成膜理论,即铝合金表面形成了氧化还原微电池.溶液中的溶解氧以及加入的H2 O2可作为羟基的供体,通过改变溶液局部pH值、物质、电子和电荷浓度来影响稀土元素的氧化反应和在基体表面的沉积.铈基转化膜的耐蚀机理是阴极抑制机理,即在铝合金表面形成的铈基转化膜阻止了氧的传输和电子的转移和传递,从而阻止了阴极微区上的还原反应,防止了铝合金表面的腐蚀溶解.但该机制只强调了阴极抑制,而忽略了也可能发生的阳极抑制.同时,由于涉及到电化学动力学抑制,因此铈基转化膜有"自愈能力".本文综述了国内外铝合金铈基转化膜制备工艺的研究进展,指出了各工艺的优点和缺点,阐述了铈基转化膜主流成膜和耐蚀理论的研究,并对制备工艺的改进方向及未来理论的研究方向进行了展望.