Effect of plasma treatment on corrosion-electrochemical behavior of titanium in molten mixture of cesium and sodium chlorides

The effect of high-temperature pulsed plasma (HTPP) on the corrosion-electrochemical behavior of titanium in a molten eutectic mixture of cesium and sodium chlorides in an argon atmosphere at temperatures of 790–810 K is studied. Upon the HTPP treatment in an oxygen or helium environment, a modified corrosion-resistant layer with a thickness up to 20 μm is formed on the titanium surface and decreases the corrosion rate of titanium in a chloride melt by a factor of 10–16.     

Features of the corrosion-electrochemical behavior of titanium with a nano- and submicrocrystalline structure

The measurements of the corrosion potential and the analysis of the polarization characteristics revealed that titanium VT1-0 with a nano- and submicrograin structure exhibits higher electrochemical activity in a 0.9% NaCl solution than its macrograin analogs. The formation of anode oxide films on the surface of titanium with structures of all types in various modes, including the microarc one, reduces the respective parameters and makes them closer, but it does not eliminate the differences inherent in the original substrates.     

BN对AlN耐火材料烧结性能及抗钛熔体侵蚀性能的影响

以新型耐火材料AlN为基体,添加不同含量的高活性h-BN及烧结助剂Y2O3,在1850 ℃保温4 h下无压烧结制备出无氧、易加工的AlN/BN耐火复合陶瓷,分析了该复合陶瓷的显微组织,研究了其与TiAl熔体的界面润湿规律及界面反应。结果表明,BN颗粒的加入可以有效填充AlN颗粒间隙,促进复合陶瓷的烧结致密化,当添加5 wt% BN颗粒时,复合陶瓷致密度达到最高,为89.24%。复合陶瓷的组织由AlN、BN及钇铝酸盐Y4Al2O9组成,其中Y4Al2O9主要分布在AlN颗粒界面处。BN颗粒可以降低复合陶瓷与TiAl熔体的界面润湿性,其中含5 wt% BN的复合陶瓷与TiAl熔体的界面润湿角约为136°,表明二者润湿较差,复合陶瓷表现出良好的化学惰性。界面反应实验发现复合陶瓷具有良好的抗TiAl熔体侵蚀性能,其与TiAl熔体的界面平整清晰,界面层厚度为9.5 μm,未发生明显元素扩散,表明了AlN/BN复合陶瓷是一种极具潜力的钛合金熔炼用耐火材料。     

Effect of Ti-OH formation on bioactivity of vacuum plasma sprayed titanium coating after chemical treatment

The effect of Ti-OH groups on bioactivity of NaOH treated titanium coating was investigated in this paper. The NaOH-heat treatment was also applied to modify the titanium coating for comparison. The results show that the amount of Ti-OH groups was important to induce apatite formation on the treated titanium coating. When the NaOH treated titanium coating was exposed to SBF, it released Na⁺ ions from the sodium titanate layer on its surface into the SBF via exchanging with H₃O⁺ ions in the fluid and Ti-OH groups were rapidly formed on the surface. So the NaOH treated titanium coating has good bioactivity in simulated body fluid (SBF). The amount of Ti-OH groups on the titanium coating was reduced after heat treatment, so the bioactivity of NaOH-heat treated titanium coating was obviously affected.     

Effect of low temperature melt on solidification structure of A356 alloy with melt thermal treatment

1　ＩＮＴＲＯＤＵＣＴＩＯＮＷｉｔｈｔｈｅｄｅｖｅｌｏｐｍｅｎｔｏｆｔｈｅｓｏｌｉｄｉｆｉｃａｔｉｏｎｔｅｃｈ ｎｏｌｏｇｙａｎｄｃｌｕｓｔｅｒｓ ,ｔｈｅｅｆｆｅｃｔｏｆｔｈｅｓｔｒｕｃｔｕｒｅｏｆｔｈｅｌｉｑｕｉｄｍｅｔａｌｏｎｔｈｅｆｉｎａｌｓｏｌｉｄｉｆｉｃａｔｉｏｎｓｔｒｕｃｔｕｒｅｉｓｐａｉｄｍｏｒｅａｔｔｅｎｔｉｏｎ[1～ 6] .Ｔｈｅｍｅｌｔｔｅｍｐｅｒａｔｕｒｅｔｒｅａｔｍｅｎｔ(ＭＴＴ)ｉｓｓｕｃｈａｐｒｏｃｅｓｓｔｈａｔｃａｎｉｍｐｒｏｖｅｔｈｅｓｏｌｉｄｉ ｆｉｃａｔｉｏｎｓｔｒｕｃ…     

The melt spinning of gamma titanium aluminides

Rapid solidification shows great promise for the production of gamma titanium aluminides, and one of the most interesting rapid solidification techniques is melt spinning. In this work, melt-spun Ti-5SAl and Ti-48Al-2Cr-2Ta (atomic percent) were produced; the resulting alloys had uniform microstructure and composition. In addition, the investigation showed the utility of a model developed to describe heat transfer and fluid flow in melt spinning.     

Effect of coupling between melt shape and temperature field on electromagnetic shaping

1　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｅｌｅｃｔｒｏｍａｇｎｅｔｉｃｃａｓｔｉｎｇｔｅｃｈｎｉｑｕｅｗａｓａｐ ｐｌｉｅｄｔｏｏｂｔａｉｎｉｎｇａｌｕｍｉｎｕｍｉｎｇｏｔｓｗｉｔｈｌａｒｇｅｃｒｏｓｓ ｓｅｃｔｉｏｎｉｎ 1980 ,ｉｎｗｈｉｃｈｌｏｗｅｌｅｃｔｒｉｃｃｕｒｒｅｎｔｆｒｅ ｑｕｅｎｃｙｗａｓｕｓｕａｌｌｙｓｅｌｅｃｔｅｄ[1～ 5] .Ｉｎｏｕｒｌａｂｏｒａｔｏｒｙ ,ｔｈｅｒｅｓｅａｒｃｈｉｓｆｏｃｕｓｅｄｏｎｔｈｅｅｌｅｃｔｒｏｍａｇｎｅｔｉｃｓｈａｐｉｎｇｏｆｂｌａｄｅ ｌｉｋｅａｎｄｔｈｉｎ ｐ…     

熔体处理对A357合金枝晶搭接点的影响

采用双热电偶法分别测得不同熔体处理A357合金的枝晶搭接点，进而通过热分析法分别计算出枝晶搭接点的固相体积分数fs^coh。结果表明，冷却速率和晶粒细化处理对fs^coh的增大有较大影响；而变质剂（Sr）对fs^coh值的影响不明显。分析表明，冷却速率的提高以及晶粒细化剂的加入细化了晶粒和延缓枝晶的生长，从而提高fs^coh，而Sr的加入只改变Si的形态，对fs^coh的影响不大。     

Effect of melt treatment on impact toughness of 356 type alloys

The effects of melt treatment in particular the types of grain refiners as well as Sr modification on the impact properties A356·2 alloys in as cast and heated treat conditions have been investigated. The results show grain refining is very effective parameter in improving the alloy toughness when the alloy is well modified. The best values for total absorbed energy of T6-tempered alloys are achieved after using 0·04%Ti in the form of Al–5%Ti–1%B and Al–10%Ti master alloys. A significant degradation in impact properties is observed due to the Sr–B interaction in some cases leading to the formation of Sr₆B compound. The improvements in toughness are mainly due to the change in silicon particle morphology and to the dissolution and fragmentation of intermetallics during the solution heat treatment process at 540°C for 8 h prior to quenching and artificial aging.     

Effect of melt pulse electric current and thermal treatment on A356 alloy

Effects of the melt pulse electric current and thermal treatment on solidification structures of A356 alloy were investigated.In the experiments.the low temperature melt(953K and 903K)treated by pulse electric current was mixed with high temperature metl(1223K).By the control experiments,the results show that the solidification structure of A356 alloy is refined apparently by the pulse electric current together with melt thermal treatment process,and the mechanical properties.especially the elongation ratio of the specimen treated is improved greatly.The structure change of the melt by pulse electric current and melt thermal treatment is the main reason for the refinement of the solidification structure of A356 alloy.     

熔体温度处理工艺对A319合金组织和性能的影响

研究了熔体温度处理工艺对A319合金凝固组织的影响,通过对冷却速度和混合熔体停留时间的考察,发现不同的冷却速度对经过和不经过熔体温度处理的凝固组织初生枝晶尺寸作用不大,但对凝固组织中的晶间化合物相的析出有很大影响。研究结果表明,熔体温度处理工艺有利于抑制晶间化合物的析出,促进组织的均匀性,随着混合熔体停留时间的延长,试样的拉伸性能表现出由低到高,再由高到低的变化规律,从原子团族的角度分析了熔体温度处理工艺对凝固组织的作用机制。     

功率超声对纯铝凝固组织的影响

对1.5 kg的纯铝熔体进行了功率超声辅助凝固试验,研究了功率超声对不同纯度纯铝凝固组织的影响,并比较了机械搅拌与功率超声的细化效果。结果表明,功率超声可以有效细化w(Al)=99.7%工业纯铝以及w(Al)=99.992%高纯铝的凝固组织。功率超声与机械搅拌相比,所获得的凝固组织更均匀且不易产生铸造缺陷。基于结晶游离理论讨论了功率超声的细化机制。功率超声的空化作用促进了超声耦合头附近液面的异质形核,声流作用则促进了晶粒的游离和沉淀。此二者的综合效应是等轴晶区形成的主要原因。     

Producing a microporous structure on titanium alloys by means of plasma surface treatment

It has been demonstrated that, with application of plasma methods of treatment of the surface of titanium alloys with subsequent selective chemical etching (on the example of the VT1-0 alloy), a microporous titanium–based structure is formed. The results of laser and electroarc treatment of the surface have been presented, and its composition, size, and pore structure have been determined.     

熔体温度处理对不同成分铝合金凝固组织和性能的影响

运用熔体温度处理工艺 ,研究了A35 6铝合金中Cu ,Fe ,Mg成分的变化对凝固组织及性能的影响。组织观察和性能测试结果表明 ,熔体温度处理工艺能够明显抑制富Cu、富Mg、富Fe等金属间化合物相的析出 ,改善和减小了富Cu、富Mg、富Fe相析出形貌和尺寸 ,显著地提高合金力学性能。用团簇理论分析和解释了有关的实验现象和结果。     

Antibacterial properties of vacuum plasma sprayed titanium coatings after chemical treatment

Implant-related infection is one of the common clinical complications that cause high rates of mortality and morbidity in orthopedic surgery. Endowing implant antibacterial properties is a useful method to reduce such infection. In this paper, vacuum plasma sprayed titanium coatings were treated by NaOH solution firstly, and then antimicrobial silver was introduced into the coatings by immersing in 0.02 mM (denoted as CA1), 0.06 mM (denoted as CA2) and 0.1 mM (denoted as CA3) Ag⁺ containing calcification solution. Antibacterial property of the treated titanium coatings was examined by employing three types of bacteria stains, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. X-Ray diffraction and scanning electron microscopy were used to observe the phase composition and surface morphology of the modified titanium coatings. Results showed that all of the three kinds of coatings exhibited more than 90.00% antibacterial ratio except CA1 to Staphylococcus aureus which is 63.30%. The release of silver in physiological environment was monitored and it was found that the excellent antibacterial property of the treated coatings was attributed to the release of silver.     

Effect of thermomechanical treatment on the crack resistance of titanium alloys

Conclusion The optimal thermomechanical treatment of dual-phase titanium alloys, which contributes to their improved crack resistance, consists of deformation in the lower portion of the -region+deformation in superplasticity regimes+quenching from the deformation temperature+aging. In this case, maximum hardening is also achieved.A. A. Baikov Institute of Metallurgy. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 49–50, May, 1990.     

超声波熔体处理方法对纯铝铸锭凝固组织的影响

研究了超声波熔体处理方法对纯铝铸锭凝固组织的影响，分析了没有添加除气剂不进行超声波处理、只添加除气剂不进行超声波处理、既添加除气剂又进行超声波处理的情况，以及超声波对纯铝凝固组织影响的原因。研究结果表明，采用合适的超声波振动处理时间，可以提高铸锭晶粒的细化率。     

熔体过热处理对AZ31镁合金凝固组织的影响

研究750、800、850、900和950℃不同熔体过热处理温度对AZ31镁合金凝固组织的影响规律.利用光学显微组织定量分析经不同温度过热处理所得AZ31镁合金的二次枝晶间距等组织特征差异;开发一种采用能谱分析结果计算Mg、Al和Zn等主要元素在一个枝晶单元内各个特征区域质量分数的方法,用以测评不同过热温度下凝固组织的成分均匀性.结果表明:当过热温度从750℃增加到900℃时,成分偏析减少,铸态组织中二次枝晶间距从13μm减小到9μm,多点随机显微硬度的平均值从36.5 HV增大到42.6 HV;AZ31镁合金较理想的熔体过热处理温度为900℃.     

Effect of ultrasonic melt treatment on microstructure of A356 aluminium cast alloys

Abstract

A systematic study of the effect of ultrasonic treatment on the structure of the A356 Al–Si–Mg alloy was carried out. Ultrasonic vibrations were applied to the melt at several temperatures (628 to 608°C) for different periods (0–180 s). The results showed that the ultrasonic treatment is effective in controlling the morphology and size of aluminium grains when applied between 619 to 626°C, and is very effective at 622–625°C, where fine non-dendritic grains are formed. Grain sizes smaller than 60 μm and roundness values of 0˙7 and higher were achieved by 15 s ultrasonic treatment at 623 and 620°C. At higher temperatures, the microstructures are dominantly rosette like and dendritic. At lower temperatures (below 617°C), the samples show inhomogeneous microstructures in terms of grain size and morphology. The current results are useful to set some process parameters for the ultrasonic treatment of liquid Al–Si–Mg foundry alloys prepared for semisolid processing.