Effect of novel surface treatment on corrosion behavior and mechanical properties of a titanium alloy

A new surface treatment process is presented that improves the properties of Ti-6Al-4V alloy.This process is based on thermal oxidation,in which the surface properties of the titanium alloy are improved via simultaneous nitriding and oxidation.The test results indicate that the resulting surface layer consists of TiO 2 and TiN.The sample with the best mechanical properties and corrosion resistance was sintered at a temperature of 800℃.

Effects of substrate surface treatments on hybrid manufacturing of AlSi7Mg using die casting and selective laser melting

To balance the manufacturing cost and customizability of automotive parts,a hybrid manufacturing process combining die-casting and selective laser melting(SLM)is proposed:starting with a conventional cast substrate,SLM is utilized to add additional geometric elements on top of it.For this hybrid process,the first priority is to prepare a substrate surface suitable for the subsequent SLM addition of the top-on elements.In this study,the original cast surface of AlSi7Mg was processed by sandblasting,wire electro-discharge machining,and laser remelting,respectively.Then,additional AlSi7Mg components were built on both the original cast and treated surfaces through SLM.After hybrid builds,these surfaces and resultant interfaces were examined by optical and scanning electron microscopes.Results indicate that the defect-free metallurgical joint between the cast and additively added parts can be formed on all surfaces except for the one processed by electro-discharge machining.The observed epitaxial grain growth crossing the interface implies a strong connection between the cast and the SLMed component.Despite these benefits,also mismatches in microstructure,residual stress level and element distribution between the two parts are identified.After a comprehensive assessment,laser remelting with no additional machining is recommended as the optimal surface treatment preceding SLM fabrication,because of its user-friendly operation,low cost,and high industrial feasibility.

Influence of T6 heat treatment on A356 and A380 aluminium alloys manufactured by thixoforging combined with low superheat casting

The effects of T6 heat treatment on thixoforged A356 and A380 aluminium alloys were studied.Low superheat casting(LSC)technique was carried out to prepare proper specimens for thixoforging process.The samples were poured at 20°C above their liquidus temperatures which provided the formation of equiaxed grains instead of dendritic growth.Produced billets were reheated for varied time from 20 to 80 min and thixoforged with 50%deformation rate.After thixoforging process,the samples were T6 heat treated for both A356 and A380 alloys.The microstructural evaluation and hardness alteration of thixoforged,solution treated and aged specimens were examined comparatively by using optical microscopy,scanning electron microscopy with energy-dispersive X-ray spectroscopy and Brinell hardness equipment.T6 heat treatment provided relatively uniform microstructure with newly formed precipitates that are Mg2Si and Al2Cu for A356 and A380 billets,respectively.Accordingly,hardness after artificial aging was increased considerably and reached HB 93 for A356 and HB 120 for A380 alloys.

Printing on Anodized Aluminium Surface

Anodizing of aluminium is widely applied when a controllable morphology and properties of the surface are required. Anodic oxide films may be developed by appropriate selection of electrolyte and film-forming conditions for various applications in the fields of architecture, aerospace, electronics, packaging and printing. In the present study, the printability of aluminium with respect to anodizing conditions is discussed. In particular, AA1050 alloy specimens were anodized in either sulfuric acid or phosphoric acid at temperatures ranging from 10?C to 40?C, thereby affecting the porosity and anodic layer thickness. Both the porosity and oxide thickness increase with the temperature, whereas anodization in phosphoric acid produces thinner and more porous layer than that in sulfuric acid. After the anodization step, two different printing techniques were used (i.e. digital printing and screen printing). Printed specimens were characterized by means of colour parameters, microscopy, adhesion and light fastness test. Colour parameters and ink adhesion measurements indicate that both digital and screen printing techniques give a better print quality when the anodization step is conducted in the range of 20?C - 30?C.

A Comparison of Laser Cladding Ni-based Coating on an Aluminium Alloy with CO_2 Laser and Nd: YAG Laser

In this paper, a plasma sprayed coating (Ni Cr B Si) on an Al Si alloy surface was melted by a CO 2 laser and a Nd:YAG laser respectively. The difference on the outline of the melted zone, chemical composition and hardness distribution of the laser melted zones were investigated. Experimental results showed that samples treated by the Nd:YAG laser have a better cladding tendency, more uniform chemical composition and microhardness distribution. Samples treated by the CO 2 laser have larger compositional segregation and poorer microhardness distribution.

Influence of Mg addition and T6 heat treatment on microstructure,mechanical and tribological properties of Al-12Si-3Cu based alloy

The aim of the present study was to investigate the influence of Mg addition and T6 heat treatment on microstructure,mechanical and tribological properties of the Al-Si-Cu-Mg alloys.In this context,a series of Al-12Si-3Cu-(0.5-2.5)Mg(wt.%)alloys were produced by permanent mould casting,and then subjected to T6 treatment.Their microstructure and mechanical properties were investigated using OM,XRD,SEM,EDS along with hardness,tension,compression and Charpy impact tests.Dry sliding friction and wear properties of the alloys were studied using a ball-on-disk type tester.It was observed that the microstructure of as-cast Al-12Si-3 Cu-Mg alloys consisted of a(Al),Si,O-CuAb,0-Mg_(2)Si,0-AbMg_(8)Cu(2)Si_(6) and π-AhMg_(3)FeSi_(6) phases.T6 heat treatment gave rise to nearly spherodization of eutectic Si particles,formation of finer 0-CuAH and 0-Mg_(2)Si precipitates and elimination of Chinese script morphology of 0-Mg_(2)Si phase.The addition of Mg up to 2.5 wt.%decreased the hardness,tensile and compressive strengths,tensile elongation and impact toughness of the as-cast and T6-treated alloys and increased their friction coefficient and volume loss.T6 treatment,on the other hand,led to a significant increase in mechanical properties and wear resistance of as-cast alloys.

Improving the high cycle fatigue property of Ti6Al4V ELI alloy by optimizing the surface integrity through electric pulse combined with ultrasonic surface rolling process

To improve the surface integrity and high cycle fatigue property of Ti6Al4V ELI alloy,the electric pulse has been introduced into the ultrasonic surface rolling process(USRP),which is called electric pulse-assisted ultrasonic surface rolling process(EUSRP).With the help of“electroplasticity”of the electric pulse,the thickness of the surface gradient deformation layer was about three times of the USRP specimens by adjusting the pulse current level.However,the surface hardness decreases due to the continuous effect of the pulse current and the“skin effect”during treatment.It is worth noting that the higher the applied pulse current,the more severe the softening.This paradox causes the fatigue performance of EUSRP specimens lower than that of USRP specimens.To break this paradox,the EUSRP treatment is followed by a USRP treatment.The EUSRP-2(with a pulse current of 200 A)+USRP specimens exhibit excellent surface hardness,a gradient deformation layer thickness of about 400μm,low surface roughness and high compressive residual compressive stress.Besides,the hardening mechanisms of the different surface strengthening specimens have been quantitatively analyzed in combination with microstructure analysis.The fatigue life of Ti6Al4V ELI alloy can be improved by about 25 times at 780 MPa using the EUSRP-2+USRP treatment,the main reason for the highest fatigue life is the deepest surface gradient layer and the deepest crack initiation site.The fatigue limit of the EUSRP-2+USRP specimens is not the highest because too much surface hardening causes compressive residual stress relaxation during cycling and the beneficial effect of compressive residual stress is eliminated.

焊前处理方式对LF6铝合金扩散焊的影响

利用Ｇｌｅｅｂｌｅ－１５００热／力模拟试验机，研究了ＬＦ６铝合金的扩散焊工艺。通过对焊接温度、压力、时间的调整和选用不同的焊前处理方法，确定了最佳的扩散焊工艺规范。研究结果表明：在一定的温度和时间范围内，ＬＦ６铅合金扩散焊接头的剪切强度随焊接温度和时间的增加而提高；化学浸蚀法比机械打磨法能更有效的去除铝合金表面的氧化膜；在现有试验条件下，得到ＬＦ６铝合金扩散焊的最佳规范参数，搭接试样扩散焊接头的剪切强度可达１４７．２Ｍｐａ。

渗碳热处理后18CrNiMo7–6合金钢表面变质层J–C损伤失效参数研究

合金钢在经过渗碳热处理后会在表面形成变质层。在表面变质层内,材料的力学性能沿深度方向发生变化。针对渗碳热处理后的18CrNiMo7-6合金钢的表面变质层,提出了确定Johnson-Cook损伤参数分层测试方法。通过对材料变质层进行分层线切割,得到不同变质层深度下的薄板试样;为获得不同应力三轴度下的拉伸结果,预制了不同断裂方向的拉伸剪切试样,通过试验与仿真相结合的方法,确定了考虑应变累积效应的应力三轴度并测定了材料失效应变与应力三轴度的关系;采用宽脉冲拉伸系统测定了拉伸试样的失效应变与应变率的关系。研究结果表明,同一层材料的失效应变随应力三轴度的增大而减小,在同一应力三轴度水平下,失效应变随层深增大而增大;不同层深处的试样均具有明显的应变率弱化效应,且在同一应变率水平下,失效应变随层深增大而增大;基于测量参数的拉伸过程数值仿真与试验数据的对比验证了所测定参数的准确性。

Microstructural evolution and mechanical properties of thixoformed A319 alloys containing variable amounts of magnesium

The effects of Mg content on the microstructure and tensile properties of thixoformed A319 alloys were studied. The samples were thixoformed at 50% liquid content and some of the thixoformed samples were subjected to the T6 heat treatment. The samples were then examined by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy and X-ray diffraction (XRD) analysis as well as tensile tests. The results showed that magnesium was able to refine the eutectic silicon in the samples. It was also observed that a compact Al9FeMg3Si5 phase was formed when the magnesium content was 1.0% and 1.5%. The results also revealed that as the magnesium content in the alloy increases, the tensile strengths of the thixoformed alloys also increase. The ultimate tensile strength, yield strength and elongation to fracture of the thixoformed A319 heat treated alloy were 298 MPa, 201 MPa and 4.5%, respectively, whereas the values of the thixoformed heat treated alloy with 1.5% Mg content were 325 MPa, 251 MPa and 1.4%, respectively. Thixoformed A319 alloy showed a dimple fracture behaviour, while thixoformed A319 alloys with 1.5% Mg showed a mixed mode fracture behaviour, where dimple and cleavage ruptures were seen on the fracture surface of the samples.

退火和深冷处理对7075铝合金滚磨光整加工性能的影响

为探索冷热处理对7075铝合金试件滚磨光整加工效果的影响,对原始态、退火态和深冷态(深冷处理9 h)试样进行滚磨光整加工实验和摩擦磨损实验,记录加工过程中试件表面粗糙度值和质量等数据,采用扫描电子显微镜和超景深光学显微镜,表征试件的表面形貌和磨痕形貌,采用能谱仪分析磨痕表面元素的成分。结果表明,滚磨光整加工后,深冷态试样表面粗糙度下降率和材料去除率较原始态有明显提高,且表面一致性高,表面光亮度最好。摩擦磨损实验中,深冷态试件的摩擦系数波动最小,总体变化更加平稳,其磨损机制主要为粘着磨损。

Effect of Surface Polishing Treatment on the Fatigue Performance of Shot-Peened Ti–6Al–4V Alloy

In this study, shot peening is applied to the titanium alloy Ti–6Al–4V, and the surface treatment effect on fatigue life of shot-peened specimens under high cycle loading is investigated. The induced residual stress is measured by using the orbital hole-drilling method. Surface profilometer and optical microscopy are employed to characterize the surface roughness and morphology. The deformed microstructure layers of the shot-peened specimens are investigated by using scanning electron microscopy. Experiments reveal that the fatigue life of Ti–6Al–4V is improved by the shot peening process, and the surface pre-peening polishing. The combination of pre-and post-peening polishing treatments further improves fatigue life of Ti–6Al–4V specimens. The present work provides useful guidelines for developing more efficient shot peening strategies.

铝及其合金材料表面处理研究进展

较系统地评述了近年来铝及其合金材料在表面处理方面取得的研究进展。阳极氧化方面主要介绍了硬质阳极氧化和复合阳极氧化等方面的研究成果；表面转化膜方面主要介绍了稀土转化膜以及无机非金属转化膜等在该方面取得的最新研究成果；文中还较详细地介绍了微弧氧化技术以及电化学陶瓷成膜技术在铝及其合金材料表面强化处理方面的研究进展。

铝合金激光熔覆处理等离子涂层的显微组织

利用５ｋＷＣＯ２激光器，对ＡｌＳｉ合金表面的等离子涂层（ＮｉＣｒＢＳｉ）进行熔覆处理。ＳＥＭ，ＴＥＭ和Ｘ射线衍射分析结果表明，激光合金层中的组织以铝镍金属间化合物（Ａｌ３Ｎｉ，Ａｌ３Ｎｉ２，ＡｌＮｉ和ＡｌＮｉ３）为主。在激光熔化层的表面，有富铝的Ａｌ３Ｎｉ相存在；而在激光熔化层的内部，则有富镍的ＡｌＮｉ３相存在。一些非晶组织出现在激光熔化层亚表层中，使得该区域有较高的硬度（平均ＨＶ９５２），是原等离子涂层的３倍和铝合金基底的１２倍。

铝及铝合金仿木纹着色技术

综述了铝及铝合金的性能、应用领域、表面处理的方法及将来的发展趋势。着重阐述铝及铝合金仿木纹着色的发展潜力、仿木纹着色不同方法及其特点和木纹形成原理,尤其对电化学法形成木纹的不同工艺及原理作详细的论述,其中包括电化学法木纹处理工艺的体系及组分作用、去膜工艺、阳极氧化、着色和封闭等工序,提出了铝及铝合金仿木纹着色的应用前景及未来发展方向。

铝合金表面激光熔覆研究现状

总结了铝合金表面激光熔覆的特点,评述了铝合金表面激光熔覆技术的处理工艺和熔覆体系的研究现状,分析了各种熔覆层的组织特征及性能,阐明了铝合金激光表面熔覆存在的主要问题和改进途径,并提出了今后的任务。

铝合金构件的原位快速表面处理方法研究

着重探讨了在外场操作条件下 ,对航空铝材进行原位、快速表面处理的几种方法以及不同表面处理对粘接效果的影响。结果表明 :对受损的通用航空铝合金 (LY12 -CZ)表面 ,采用自行研制的酸膏进行氧化处理 ,能造就具有一定特征形貌的铝合金表面氧化层 ,从而使粘接强度提高 76 .0 % ,并可实现对构件表面的快速、原位处理 ,能满足装备构件外场修复的基本要求。

飞机蒙皮表面预处理的研究进展

综述了飞机铝蒙皮表面预处理技术的研究进展,讨论了铝及其合金表面防腐蚀处理的各种方法以及新工艺。

表面处理对5083铝合金板胶接性能的影响

以α-氰基丙烯酸酯类瞬干胶为胶粘剂,采用剪切试验、接触角试验和扫描电镜观察系统研究了丙酮简单清洗、喷砂处理、阳极氧化处理以及偶联剂处理对5083铝合金板胶接接头剪切强度的影响。结果表明:经简单清洗后,所得胶接接头的剪切强度最低;在附着力和机械啮合的共同作用下,喷砂处理和阳极氧化处理胶接接头的强度得到了提高,其中阳极氧化处理的效果最为明显,与简单清洗胶接接头相比,剪切强度提高了223.1%;胶接前适当使用偶联剂可以使简单清洗和喷砂处理胶接接头的剪切强度提高,在该试验条件下,KH-550偶联剂体积分数为5%时,胶接接头的剪切强度均达到了最大值;但偶联剂使阳极氧化处理形成的纳米小孔不能发挥机械啮合作用,所得胶接接头的剪切强度相比未使用偶联剂的反而降低。

镁合金表面低温熔盐电镀铝研究进展

综述了镁合金表面低温熔盐电镀铝的研究进展,并介绍了低温熔盐电镀铝在镁合金表面处理上的应用前景。