Effects of Yttrium Addition on Microstructure, Hardness and Resistance to Wear and Corrosive Wear of TiNi Alloy

TiNi alloy has a high resistance to wear and could be an excellent candidate for various tribological applications. In this paper, it was demonstrated that by addition of yttrium, hardness properties and resistance to wear and corrosive wear of TiNi alloy were improved. New yttrium rich regions were formed in microstructure of TiNi alloy. The improved properties of this alloy by the yttrium addition could be attributed to the formation of these regions. The results showed that there was an optimum content for addition of yttrium between 2% and 5% (in wt%), and above this content the improvement in properties of TiNi became minor.     

Effects of Mo and Zr on Microstructure, Mechanical Properties and Wear Resistance of Fe-Al Based Alloys

In this work the microstructure, mechanical properties and wear resistance of Fe-Al based alloys with various alloying elements were studied. The microstructures were examined by optical and scanning electron microscopy （SEM） equipped with an energy dispersive X-ray spectroscope （EDS）. Two types of alloys were prepared by vacuum arc melting. One is Fe-28Al based alloys （D03 structured） with and without alloying elements such as Mo and Zr. The other one is Fe-35Al based alloys （B2 structured） produced with the same manner. For both types of alloys, Mo addition had found to exhibit an equiaxed microstructure, while dendritic structure was observed to show the effect of Zr addition. These microstructural features were more evinced with increasing content of alloying element. Concerning the mechanical properties and wear resistance, Fe-35Al based alloys were superior to Fe-28Al based alloys over the whole temperature range investigated.     

Numerical Simulation of Mechanical Behaviors of the TiNi Shape Memory Alloy Welded Joints in the Precise Pulse Resistance Butt—Welding

The hysteresis unit system was introduced to mechanical structure behavior of the TiNi SMA joint based on the structure characteristics of the martensite variants in the joints, and some functions reflecting its inner structure characteristics and micro-behavior such as density function, phase transformation function were set up from micro-points. Finally, the structure behavior relationship and corresponding mathematic model reflecting the relationship among hysteresis strain, stress and phase transformation strain were provided, which could predict the stress-strain behavior of the TiNi SMA joint to large extent.     

TiNi形状记忆合金丝在约束态热循环后的力学特性

研究了TiNi形状记忆合金丝在约束态热循环后的应力-应变特性.结果表明,如果停止加热并加载,或者在母相状态下冷却但是尚未发生正相变时加载,加载应力-应变曲线首先呈线弹性关系,然后才出现应力平台.如果在冷却过程中发生正相变的时候停止冷却并加载,则加载应力-应变曲线只出现应力平台.与之相似,如果在约束态冷却过程中停止冷却并卸载,卸载应力-应变曲线首先呈线弹性关系,然后才出现应力平台.如果在加热过程中停止加热并卸载,则卸载应力-应变曲线立即出现应力平台.     

TiNi记忆合金电子束熔覆层的组织性能研究

目的利用电子束熔覆技术将TiNi记忆合金熔覆在TC4的表面,开展熔覆层耐磨性能研究,以此来改变材料的表面性能,达到实际应用的要求。方法通过SEM、EDS、维氏显微硬度计和摩擦磨损试验机,对熔覆层的宏观形貌、显微组织、元素分布、显微硬度以及摩擦磨损性能等进行测试分析。结果制备出的熔覆层表面成形良好、无气孔、无裂纹,并且与基体实现了良好的冶金结合。熔覆层由表及里的硬度升高,其值最高可达HV625,较TC4母材(HV350)的硬度有明显的提高。通过磨损试验曲线表明,TiNi合金熔覆层和TC4基材稳定后的平均摩擦因数为0.052和0.169,比磨损率为0.96×10~(-4)和2.28×10~(-4) mm~3/(N·m)。结论TiNi熔覆层的耐磨性能较TC4基材的耐磨性能显著增强,可以达到减磨的效果。     

镁合金微弧氧化膜的耐蚀性及其在腐蚀介质下的磨损行为

在硅酸盐电解液体系中,采用电流密度为40mA/cm2的脉冲电流模式对AZ91D镁合金进行微弧氧化处理,在其表面获得均匀的陶瓷膜层。随后对膜层的形貌、耐腐蚀性及其在腐蚀介质下的摩擦磨损行为进行了研究;结果表明:微弧氧化膜具有双层结构(疏松层和致密层),表面均匀,局部有裂纹;微弧氧化处理提高了镁合金的耐腐蚀性,经微弧氧化处理后试样的自腐蚀电位升高了94mV;在腐蚀环境下,膜层的耐磨性会降低,膜层磨损的机理随载荷大小不同而改变,小载荷时主要是磨粒磨损,高载荷时主要是结合力破坏而导致的剥层磨损。     

Effect of Si3N4 Addition on the Mechanical Properties, Microstructures, and Wear Resistance of Ti-6Al-4V Alloy

In order to improve the wear resistance of Ti-6Al-4V, different amounts of Si3N4 powder were added into the alloy powder and sintered at 1250℃. Porous titanium alloy with higher wear resistance was successfully fabricated. At sintering temperature, reaction took place and a new hard phase of Ti5Si3 formed. The mechanical properties of the fabricated alloys with different amounts of Si3N4 addition were investigated. The hardness of Ti-6Al-4V, which is the index of wear resistance, was increased by the addition of Si3N4. Amounts of Si3N4 addition have very significant influences on hardness and compressive strength. In present study,titanium alloy with 5 wt pct Si3N4 addition has 62% microhardness and 45% overall bulk hardness increase,respectively. In contrast, it has a 16.4% strength reduction. Wear resistance was evaluated by the weight loss during wear test. A new phase of Ti5Si3 was detected by electron probe microanalyzer （EPMA） and X-ray diffraction （XRD） method. The original Si3N4 decomposed during sintering and transformed into titanium silicide. Porous structure was achieved due to the sintering reaction.     

Microstructure and Wear Resistance of in situ Formed Duplex Coating Fabricated by Plasma Nitriding Ti Coated 2024 Al Alloy

In this study, plasma nitriding was carried out on pure titanium film coated 2024 Al alloy to improve its surface mechanical property. Ti film with the thickness of 3.0 mm was firstly fabricated by means of magnetron sputtering method. Then, the Ti coated specimen was subjected to plasma atmosphere comprising 40% N2e60% H2 at 430 C for 8 h. The microstructures of the nitrided specimens were characterized by X-ray diffraction and scanning electron microscopy. Microhardness tester and pin-on-disc tribometer were used to test the mechanical properties of the untreated and nitrided specimen. The results showed that the surface of the nitrided specimen was composed of three layers（i.e. the outside nitride Ti N0.3layer, the middle Al3 Ti layer and the inside Al18Ti2Mg3 layer）. The surface hardness and wear resistance of 2024 Al alloy were increased simultaneously by duplex treatment. The untreated specimen exhibited severe adhesive wear while the nitrided one behaved in middle abrasive wear.     

Effect of Y Addition on Microstructure and Mechanical Properties of Friction Stir Welded ZK60 Alloy

6 mm thick ZK60 and ZK60-Y alloy plates were successfully friction stir welded (FSW) at a tool rotation rate of 1200 r/min and a traverse speed of 100 mm/min.FSW resulted in the dissolution of MgZn2 particles in the ZK60 and the breakup and dispersion of W-phase (Mg3Zn3Y2) particles in the ZK60-Y alloy, thereby leading to a decrease in the hardness of the nugget zone (NZ) for the ZK60 alloy and an increase in the hardness of the NZ for the ZK60-Y alloy, respectively.While two FSW joints exhibited similar joint efficiency (87%-89% of ultimate tensile strengths of the parent materials), the yield strength of the FSW ZK60-Y joint was substantially higher than that of the FSW ZK60 joint.The fracture occurred in the NZ and the heat affected zone for the ZK60 and ZK60-Y joints, respectively, which were consistent with the lowest hardness distribution of the welded joints.     

TiNi形状记忆合金的相变行为及其影响因素

对近年来有关ＴｉＮｉ形状记忆合金的相变行为及其影响因素等方面的最新研究成果综合评述，主要内容包括化学成分，应力／应变，热／机械循环，冷／加热和热处理制度等因素对相变温度和相变次序的影响。     

粉煤灰复合涂层腐蚀磨损性能研究

采用粉煤灰为主要原料,在Q235钢基体上制备了热化学反应型复合涂层,分别利用X射线衍射仪(XRD)和扫描电镜(SEM)对涂层进行物相分析和截面形貌观察,并模拟了复合涂层在石油介质中的腐蚀磨损行为。XRD分析结果表明,有Na2B4O7、TiB2、NaB15和Al6O13Si2等新相生成,获得了玻璃/陶瓷复合涂层;由SEM观察可知,界面处结合紧密,涂层致密且孔隙率低;热震实验结果表明,粉煤灰复合涂层热震次数达50次以上,结合强度良好;石油介质腐蚀磨损实验表明,在200r/min、300r/min和400r/min的条件下,复合涂层的抗腐蚀磨损性能分别为基体的2.74倍、2.78倍和1.80倍。     

近等原子比钛镍合金氩弧焊接接头的组织和性能

借助金相显微镜、拉伸实验和弯曲回复法等手段研究了近等原子比钛镍形状记忆合金氩弧焊接接头的组织和性能。研究结果表明,近等原子比钛镍形状记忆合金氩弧焊接接头的显微组织可分为三个区,分别是粗大柱状晶区、细小柱状晶区和热影响区。由于焊接接头显微组织与母材之间的差别,在相同的应变下,近等原子比钛镍形状记忆合金氩弧焊接接头的回复温度明显高于母材,记忆性能变差。焊接后的近等原子比钛镍形状记忆合金的屈服强度与母材相近,但抗拉强度和延伸率远低于母材。氩弧焊接近等原子比钛镍合金的显微组织在热处理后不会发生明显变化,经过形变后,焊接接头的回复温度与母材仍有差别,显微组织的不同是造成这一现象的原因之一。     

Fe-Cr-C-B堆焊合金耐磨性研究

采用铺粉堆焊方式,在低碳钢表面堆焊高碳铬铁和硼铁混合合金粉末,研究了Cr、C含量对Fe-Cr-C-B堆焊合金耐磨性的影响,结果表明,随着Cr、C含量的增加,硬度逐渐增加,磨损损失逐渐减少,耐磨性增强.本试验中,当Cr含量为31.67％、C含量为3.85％,B含量为0.4％时,磨损失重最小.硼对Fe-Cr-C-B合金耐磨...     

Cu－Zn－Al－Mn－Ni－Ti合金的显微组织及力学行为

本文利用电子拉伸试验、扫描电镜、金相显微镜研究了Ｃｕ－Ｚｎ－Ａｌ－Ｍｎ－Ｎｉ－Ｔｉ合金的细化效果、断裂方式、记忆性能及伪弹性。结果表明：试验合金的铸态、轧态和淬火态组织得到明显细化。晶粒细化后合金室温拉伸断裂强度为７５０ＭＰａ，断裂应变为６．６％，同未细化的Ｃｕ基记忆合金相比强度大大提高，塑性也有所改善。低温拉伸时呈穿晶断裂，断口主要为准解理台阶；高温拉伸时呈微孔聚集型断裂。试验合金的室温完全可恢复应变为４．０％，完全伪弹性恢复应变为４．５％，均达到了多晶体材料的理论平均值。     

表面氧化对TiNi形状记忆合金耐腐蚀性能的影响

本文用腐蚀的方法,研究了表面氧化对TiNi形状记忆合金耐腐蚀性能的影响。由于经过表面氧化处理的合金耐蚀性与其表面的氧化膜密切相关,而要获得致密的氧化膜,则关系到Ti、Ni两元素的扩散、氧化,以及氧化膜的生长条件,生长速度等等,所以随着氧化温度、氧化时间、材料本身的表面光洁度、氧化速度等几个影响因素的改变,合金耐蚀性也随之变化。经过实验比较,认为可以采用500℃保温1小时,在不影响合金的形状记忆效应的前提下,以提高表面光洁度、调节真空度来控制试样的氧化速度的表面处理方式,获得质量较好、致密的氧化膜,从而抑制有毒Ni离子的释放,显著地提高TiNi合金的耐腐蚀性能和生物相容性。     

Zn添加对挤压态Mg-Al-Ca-Mn合金微观组织和力学性能的影响

目的 研究不同含量Zn元素对镁合金塑性、强度的改良效果.方法 以Mg-Al-Ca-Mn合金为基础,采用热挤压成形加工方法,分析不同Zn含量对其显微组织和力学性能的影响.结果 Zn元素可以改变挤压态镁合金的显微组织,对其主合金相影响不大,但可以改变衍射峰强度.Zn元素可以提高挤压态镁合金的屈服强度和伸长率,提高镁合金韧性...     

Influence of Carbon Nanofiber Addition on Mechanical Properties and Crystallization Behavior of Polypropylene

1.IntroductionOne of the important applications for carbon nan-otubes(CNTs)is to be used as reinforcing filler,becauseCNTs have unique mechanical properties and large as-pect ratio.Various polymers have been used as the ma-trices to investigate the reinforcing effect of CNTs[1~5].Poly(propylene)(PP)as a common plastic and semicrys-talline polymer has attracted much attention in the re-search of CNT/polymer composites,including the influ-ence of GNTs on the mechanical properties[6~10],cr…     

TiNi Shape Memory Alloy Foams Synthesized by Spacer Sintering and their Properties

Titanium （Ti） and nickel （Ni） elemental powders were blended by ball milling and the ball milled powders were employed to fabricate TiNi shape memory alloy （SMA） foams by spacer sintering. Effect of ball milling time on phase constitutes of the sintered TiNi alloy foams was studied by X-ray diffraction （XRD） analysis. Scanning electron microscopy （SEM） was used to characterize the porous structure, and compressive tests were carried out to evaluate the mechanical properties of＇the foams. Results indicate that porosities of the TiNi alloy foams can be controlled by using the spacer sintering method, and the porosities show a significant effect on the mechanical properties and shape memory effect （SME）.     

Effects of Sc Addition and Annealing Treatment on the Microstructure and Mechanical Properties of the As-rolled Mg-3Li alloy

The microstructures and mechanical properties of the as-rolled Mg-3Li and Mg-3Li-1Sc (wt%) alloys before and after annealing treatment have been investigated. Results show that the grains are refined evidently and the recrystallization temperature is improved for more than 100°C by adding 1 wt% Sc into the Mg-3Li alloy. After complete recrystallization, both the strength and ductility of the Mg-3Li alloy are improved evidently with the addition of minor Sc. The brittle fracture tendency of Mg-3Li-1Sc alloy also reduces obviously.     

微量Cu掺杂对TA10合金组织、力学性能与腐蚀行为的影响

研究了掺杂(0.5%~2.5%) Cu元素对TA10合金的微观组织、力学性能及腐蚀性能的影响,采用扫描电子显微镜(SEM)、金相显微镜(OM)研究合金的微观组织,并用XRD进行物相分析;采用电化学腐蚀、静态浸泡腐蚀试验研究合金的腐蚀性能。选出最佳合金成分,并通过原子力显微镜(AFM)对其做进一步分析。结果表明,随着Cu元素含量的增加,TA10合金基体组织被不断细化,添加2.5% Cu时,该合金的硬度值达到最大。Cu含量在1.0%~2.0%之间,合金的耐腐蚀性能较好。含Cu为0.5%的合金耐腐蚀性能优异。