Microstructure and Phase Transformation Behavior of a Stress-Assisted Heat-Treated Ti-Rich NiTi Shape Memory Alloy

In this study, the effects of stress-assisted heat treatment on the microstructure and phase transformation of a Ti-rich (Ti-49.52 at.% Ni) shape memory alloy were investigated. For this purpose, the alloy was heat treated at temperature of 500 °C for 10 h under applied stresses of 100 and 200 MPa. XRD, TEM, and repeated thermal cycling were employed to study the microstructure and transformation behavior of the heat-treated materials. Room temperature XRD diffractogram of the stress-free heat-treated material showed a weak reflection of austenite (B2), while that for the stress-assisted heat-treated materials had a high intensity implying the presence of residual austenite in the microstructure. TEM observations confirmed the presence of residual austenite and revealed mechanical twins as another constituent of the microstructure in the stress-assisted heat-treated materials. Moreover, with increasing the value of applied stress the size of mechanical twins was increased and a high density of structural defects was observed at the interfaces of the twins. DSC results demonstrated two-stage transformation in the initial cycles of transformation in the stress-assisted heat-treated material. After about eight cycles of transformation, the two-stage transformation has vanished, and a single-stage transformation remained up to 100 cycles. It was suggested that the accommodation of stresses at Ti₂Ni/matrix interface provides a suitable condition for local transformation of B2 to B19′ that is manifested by a two-stage phase transformation. Introduction of structural defects during repeated thermal cycling may counteract the stress field at Ti₂Ni/matrix interface leading to a single-stage transformation.     

等离子渗Mo的TC11钛合金摩擦磨损性能

在TC11钛合金表面等离子渗Mo以提高其耐磨性。利用SEM、EDS、XRD分析了渗Mo层的微观组织、化学成分及相组成,测定了渗层的硬度分布。采用划痕试验测定了渗层与基体的结合力。通过球盘磨损试验测定了等离子渗Mo层的摩擦磨损性能。结果表明,渗层厚度为30μm;0～10μm表层Mo含量为65%,由表及里呈梯度降低;渗层由单质Mo以及Al8Mo3和Al3Ti等化合物组成,表面硬度达1034 HV0.1;渗层与基体的结合力为70 N;渗层的比磨损率是基体的1/55.4。     

Tribological Behavior of Magnesium Alloy by Composite Treatment

A compact and homogeneous composite membranous layer was coated on the surface of AZ31 magnesium alloy by a multiple treatment of micro-arc oxidation, magnetron sputtering, and ion implantation in order to improve the wear-resistance performance and micro-arc oxidation surface of the magnesium alloy. X-ray diffraction (XRD) and metallurgical microscopy as well as scanning electron microscopy (SEM) were used to identify the phases structures of the coating and worn surface. The dry sliding wear behavior of t...     

渗氮-渗硫复合处理对Ti-6Al-4V合金摩擦学性能的影响

采用离子渗氮-渗硫复合处理在Ti-6Al-4V合金的表面形成复合渗层.用X射线衍射仪和扫描电子显微镜对复合渗层的相结构和渗层表面微观形貌进行了分析;并对复合渗层的摩擦学性能进行测试.结果表明,渗氮-渗硫复合处理,可在Ti-6Al-4V合金的表面形成具有良好减摩作用的硫化物层、次表层为具有高硬度的氮化物层和过渡层的理想的摩擦学表面.与未渗硫处理的试样相比,摩擦系数显著降低.     

几种变形铝合金与不锈钢干摩擦性能的研究

通过销-盘式摩擦磨损试验机研究了变形铝合金的干摩擦磨损性能,在干摩擦条件下测量了不同系列变形铝合金与不锈钢组成的摩擦副的磨损质量损失和摩擦系数,用扫描电镜(SEM+EDXA)观察其磨损表面及磨屑,并对其磨损机理进行了探讨分析。实验表明,在低速和室温条件下,不同系列变形铝合金平均摩擦系数不同,摩擦系数在整个实验过程中呈湍流状波动;变形铝合金的磨损机制主要以粘着、磨粒磨损为主,同时伴有氧化磨损;其中试样E#具有良好的耐磨性及干摩擦性能。     

Tribological Behavior of Plasma Mo-Alloyed Layer on TC11 Alloy under Different Loads

采用双辉等离子冶金技术制备渗Mo层,并研究其不同载荷下的摩擦行为和磨损机制。采用SEM、EDS和XRD表征渗Mo层的微观形貌、成分分布以及相结构。结果表明:渗Mo层厚度为20μm,致密均匀,其相主要为Mo、Al3Ti和Al8(Ti3-x Mox)。为了研究渗Mo层的摩擦行为,分别在载荷1.3,5.3和9.3 N对其进行滑动磨损试验。随着载荷的增加,渗Mo层的平均摩擦系数和磨损率都呈上升趋势。根据载荷1.3 N条件下的三维形貌、SEM照片和能谱分析,得出其磨损机制为轻微磨粒磨损和氧化磨损;在载荷5.3 N条件下,氧化磨损和磨粒磨损为主要磨损机制;在载荷9.3 N条件下,主要磨损机制为氧化磨损、磨粒磨损和粘着磨损。     

模拟体液中医用钛合金阳极氧化膜的摩擦行为

目的 在TC4钛合金表面获得阳极氧化膜,分析阳极氧化膜膜厚随电压变化的规律,探讨阳极氧化膜在模拟体液中的摩擦性能。方法 用强硫酸型溶液作为电解液,利用氧化还原反应,用自制的设备在TC4钛合金表面以不同的电压进行阳极氧化,在试样表面制得颜色各异的氧化膜。使用多功能材料CFT–1型表面综合性能测试仪,对阳极氧化膜在模拟体液中进行摩擦性能测试。结果 阳极电压从15 V增大到100 V,氧化膜厚度从6.2 μm 增大到28.4 μm,平均摩擦因数先增大后减小。电压升高,Rutile TiO2在阳极氧化膜的含量不断提高。氧化膜在模拟体液中的摩擦行为分为3个过程,第一阶段,各种电压的TC4合金氧化膜均在前5 min完成短时跑和;第二阶段,摩擦因数震荡上升,随着电压的升高,氧化膜磨粒磨损加剧,局部出现剥落,75 V的剥落最大,100 V的磨痕比较平整;第三阶段,摩擦因数再次爬升,15、35、60 V出现在36 min时,75 V出现在40 min时,100 V在48 min时,阳极氧化膜被磨穿。结论 氧化膜的颜色、耐磨性、物相及表面形貌受电压影响。钛合金阳极氧化膜在模拟体液中耐磨性良好,磨损类型为磨粒磨损。     

7A52铝合金表面微弧氧化陶瓷层摩擦学特性

利用微弧氧化技术在7A52装甲铝合金表面原位生成了陶瓷层,通过SEM、XRD等手段分析了陶瓷层的表面形貌和物相组成,并在MS-T3000往复式摩擦磨损试验机上考察了陶瓷层在干摩擦条件下的摩擦学行为,分析了陶瓷层的磨损失效机制.结果表明,徼弧氧化陶瓷层由α-Al2O3和γ-Al2O3陶瓷相组成,高硬度的陶瓷层提高了7A52铝合金表面接触载荷承载能力和耐磨性,耐磨性最大提高幅度达到了100倍以上.陶瓷层的磨损机制以磨粒磨损失效为主.     

纳米金刚石增强镍基合金熔覆涂层的摩擦学性能

利用真空熔烧方法在４５钢表面制备纳米金刚石粉和镍基自熔合金组成的复合涂层,利用扫描电镜分析了涂层的组织结构,测定了涂层的显微硬度,并利用ＳＲＶ磨损试验机分析了涂层的摩擦学性能。试验结果表明,涂层主要由γ－Ｎｉ固溶体和分布于其间的碳化物、合金渗碳体、合金碳化物和硼化物组成;复合涂层的我和耐磨性随内米金刚石入量的增多而提高,并且当复合涂层中添加的纳米金刚石粉的质量百分含量在０．８％－１．０％时,其耐磨     

Cyclic Oxidation Behavior of Simulated Post-Weld Heat-Treated P91

For long-term service life it is desirable that the high-temperature components posses slow-growing oxide scale. The growth and degradation of the oxide scale on P91 were studied by a thermal cycling method. The oxidation temperature was 780 °C and the duration of each cycle was 2 h. The mass gain and integrity of the scale was examined using a thermogravimetric balance. Any lack of integrity is monitored by the transient mass gain associated with the exposure of fresh surface. The scale retained the integrity throughout 100 cycles. Post-oxidation examination was carried out by scanning electron microscopy, energy dispersive spectroscopy and laser Raman spectroscopy. The nature of the scale was characterized and the reason for the compositional segregation is analyzed.     

镁合金表面微弧氧化陶瓷层摩擦学性能的研究

利用微弧氧化技术在AZ31镁合金表面原位生长陶瓷层，用球-盘磨损实验机对试样的摩擦学性能进行了研究。结果表明：AZ31镁合金表面微弧氧化后可以形成均匀的表面陶瓷改性层，改性层由疏松层、致密层和截面层组成，厚约20μm。微弧氧化处理后的试样在干摩擦小滑动距离下表现出良好的耐磨性。并用SEM，XRD分析了微弧氧化陶瓷层的显微组织、表面形貌和相结构。     

Ti6Al4V合金上类金刚石膜的摩擦学性能及腐蚀行为

采用离子束沉积技术在医用Ti6Al4V合金表面制备类金刚石薄膜（DLC）,利用原子力显微镜、Raman光谱、X射线光电子能谱（XPS）及UMT-2摩擦磨损试验机对薄膜的形貌、结构、摩擦学性能进行表征。采用动电位极化对涂层前后基底的耐腐蚀性能进行测试。结果表明：制备薄膜为类金刚石碳结构,基底偏压对薄膜形貌、结构有较大影响;偏压为–100 V时制备的薄膜表面粗糙度低（6.5 nm）,sp3/sp2 比值高,摩擦学性能优异;经DLC膜保护的合金基底耐腐蚀性能获得明显改善。     

Ti6Al4V合金上类金刚石膜的摩擦学性能及腐蚀行为

采用离子束沉积技术在医用Ti6Al4V合金表面制备类金刚石薄膜(DLC),利用原子力显微镜、Raman光谱、X射线光电子能谱(XPS)及UMT-2摩擦磨损试验机对薄膜的形貌、结构、摩擦学性能进行表征。采用动电位极化对涂层前后基底的耐腐蚀性能进行测试。结果表明:制备薄膜为类金刚石碳结构,基底偏压对薄膜形貌、结构有较大影响;偏压为-100V时制备的薄膜表面粗糙度低(6.5nm),sp3/sp2比值高,摩擦学性能优异;经DLC膜保护的合金基底耐腐蚀性能获得明显改善。     

钛合金微弧氧化陶瓷层性能

利用脉冲微弧氧化技术在钛合金(Ti6A14V)表面制备陶瓷层.用 SEM 观察了陶瓷层的表面形貌和截面显微组织,XRJ)研究陶瓷层的相组成,用球-盘磨损实验机对陶瓷层的摩擦学性能进行了研究,并用光学显微镜镜观察了磨痕的形貌.结果表明厚度约为10 μm的微弧氧化陶瓷层由疏松层和致密层组成.陶瓷层主要由金红石TiO2相和锐钛矿TiO2相构成.抛光后的陶瓷层在干摩擦小滑动距离下表现出良好的减摩作用,耐磨性能也显著增强.     

Hot Compression Mechanical Behavior of Solution Heat-Treated and Pre-aged Mg-Zn-Gd-Er Alloys

The mechanical behavior of solution heat-treated and pre-aged Mg-6Zn-1Gd-1Er alloys during hot compression (from 180 to 330 °C) has been investigated. The results showed that the flow stress curves of the pre-aged sample (PAS) intersected with that of the solution heat-treated sample (SHTS) during hot compression. At 180 °C, when the true strain is 0.27 and 0.47, the PAS showed larger and smaller stress (210.80 MPa vs. 207.58 MPa and 205.67 MPa vs. 207.93 MPa) than the SHTS, respectively. These phenomena were due to the stronger interaction of W phase and dislocations/twins under the strain of 0.27, while dynamic recrystallization softening occurred under the strain of 0.47. When the temperature increased to 330 °C, the flow stress of PAS and SHTS showed an opposite trend to that of 180 °C. Continuous dynamic recrystallization and particle stimulated nucleation based on slip operations are the main deformation mechanisms under 330 °C. At the true strain is 0.33 and 0.53, the PAS has smaller and larger stress (61.32 MPa vs. 63.69 MPa and 58.75 MPa vs. 57.09 MPa) than the SHTS, respectively. The increasing deformation resistance of dynamic precipitation improved the flow stress under smaller strain and dynamic recrystallization decreased the flow stress under high strain, which resulted the opposite phenomena of SHTS.     

激光熔覆TiZrHfCrMoW涂层在大气和模拟体液环境下的摩擦磨损行为

目的 提高钛合金表面耐磨性。方法 采用激光熔覆技术在TC4基体表面制备TiZrHfCrMoW涂层,采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)等分析涂层的相组成和显微组织结构。联合电化学工作站和摩擦磨损试验仪,分别在大气和37 ℃的0.9%NaCl模拟体液环境条件下,研究TiZrHfCrMoW高熵合金(HEA)涂层与TC4合金的摩擦磨损行为。结果 激光熔覆HEA涂层均匀致密,无明显缺陷,主要由2种BCC相及1种未知相组成,涂层平均硬度为584.6HV0.2,约为TC4基材硬度的1.6倍。在空气中滑动时,HEA涂层在0.3、0.5、1 N下的磨损率均比TC4基体低,且涂层的磨损率随载荷的增加而增加,TC4的磨损率则相反。在(37±0.5) ℃的0.9%NaCl溶液中,0.5 N载荷下TC4的磨损率是HEA涂层的6倍。HEA涂层与TC4钛合金基体相比,具有更高的自腐蚀电位和更低的腐蚀电流密度。模拟体液环境下HEA涂层的主要磨损机制为逐层剥落和腐蚀磨损。结论 激光熔覆HEA涂层可以有效提高TC4合金的耐磨损及耐腐蚀性能。     

Tribological Properties of Al Alloy Particle Composites

In recent years, a variety of particle dispersed aluminum alloy composites have been synthesized. The tribological properties of these materials include sliding wear, friction, seizure resistance and abrasive wear (of composites containing solid lubricant as well as hard ceramic particles). The potential high-performance applications of Al-alloy-graphite composites include pistons for internal combustion engines and bearings. For such applications, the low stress abrasive wear rates of composites, containing high volume fractions (0.20–0.35), are comparable to that of heat treated 1045 steel.     

Study On the Tribological Behavior of the Arc-added Glow Discharge Plasma Non-hydrogen Carburization On Titanium Alloy Surfaces

This paper introduces a new titanium alloys surface strengthening treatment by using the arc-added glow discharge plasmas non-hydrogen carburization technique. High purity and high strength graphite is selected as cooling cathode arc source for supplying carbon atoms and particle, which migrate to the titanium alloy(Ti6Al4V) surface and form modified layer. Thus, the hydrogen embrittlement is avoided while the tfibological behavior of the titanium alloy surface is improved in the respects of anti-friction and anti-wear ability.The tribological behavior of the modified layer under dry sliding against SAE52100 steel was evaluated on a ball-on-disc test rig. The results showed that the modified layer obtained a thickness of 30μm at 980℃, 30minutes. The microhardness of the Ti6Al4V alloy surface attained 936 HV, which was much larger than that of the Ti6AI4V alloy. The Ti6AI4V alloy was characterized by adhesion wear and scuffing under dry sliding against the steel, while the surface modified layer experienced much abated adhesion wear and scuffing under the same testing condition. This could be attributed to the carbon dement with different modalities exists in the modified layer.The modified layer showed good friction-reducing and fair anti-wear ability in dry sliding against the steel. Using the SEM,XRD and XPS, the phase structure and morphology of the carburization modified layer was analyzed.     

冷轧TiNi合金的阻尼行为研究

研究了冷轧变形对TiNi合金阻尼行为的影响,探讨了冷轧变形影响阻尼特性的微观机制.结果表明,当应变振幅较低时,形变马氏体的阻尼值随频率的增加先急剧下降至一定值后趋于稳定;当应变振幅较高时,频率对阻尼值的影响较小;当振动频率一定时,形变马氏体的阻尼值随应变振幅的增加而下降至一定值,随振幅的继续增大其阻尼值趋于稳定.形变马氏体的高阻尼特性主要归因于外力作用下马氏体孪晶界面及位错的往复运动.     

3D打印铝合金材料的摩擦学性能

为测试高速传动件上3D打印铝合金材料的耐磨性能,对3D打印铝合金(EOS:Al Si10Mg)与铸造铝合金(ZL1104T6:ZAl Si9Mg)进行性能对比测试。采用光学显微镜、电子扫描电镜、能谱分析仪、显微硬度计、高温摩擦磨损试验机等对两种材料进行微观组织分析,硬度测量,摩擦磨损值测定。结果表明,3D打印铝合金其微观组织下晶粒更精细,并且各合金元素分布均匀性更好;3D打印铝合金硬度平均值略高于ZL1104 T6;3D打印铝合金的摩擦因数曲线更平滑,摩擦因数平均值及磨损失重率均小于ZL1104 T6,证明在相同的摩擦磨损条件下,3D打印铝合金表现出良好的耐磨性。