激光参数对Ti6Al4V钛合金激光冲击成形的影响

研究在Ti6Al4V合金激光冲击成形过程中,不同激光参数对板料弯曲角及表层硬度的影响。结果表明:当激光功率密度小于3GW/cm2时,弯曲角随着激光功率密度线性增加,激光功率密度超过3GW/cm2时,由于表面熔化现象的出现,弯曲角出现减小的趋势;板料弯曲角随冲击次数的增加也呈线性增长,但弯曲阻力的增加使得弯曲角的增长速度逐渐减慢;随着激光功率密度的增加,材料表面冲击区的硬度增高,表面硬化层的显微硬度最高达HV490,硬化层厚度约为1.0mm。     

激光熔覆制备B_4C_p/Ni合金复合涂层的组织与性能

对Ni60合金粉末中添加B4C陶瓷颗粒的激光熔覆组织结构和力学性能做了研究。结果表明,加入陶瓷颗粒可增加熔覆层中强化相数量,提高涂层的硬度和耐磨性,在陶瓷颗粒加入量达到15%时效果最好。     

ZTC4筒形件温成形扩口数值模拟

对铸造Ti-6Al-4V筒形件温成形扩口成形工艺进行了数值模拟分析,得出了优化的工艺参数,并对凸模锥角进行了优化模拟,得出了合适的锥角。     

Phase diagrams of Li2MoO4-Na2MoO4 and Na2MoO4-K2MoO4 systems

The phase diagrams of the Li2MoO4-Na2MoO4 and Na2MoO4-K2MoO4 systems have been reassessed using differential thermal analysis together with high-temperature and room-temperature X-ray diffraction analysis. The results showed that the compound Li2MoO4.6Na2MoO4 did not exist; however, it confirmed the existence of the compound Li2MoO4.3Na2MoO4 in the Li2MoO4-Na2MoO4 systen＇ls. With regard to the system of Na2MoO4-K2MoO4, we could not confirm the results reported by Bukhanova who claimed that the system was eutectic type with 1：1 and 1：2 intermediate compounds, refuting the statement of Amadori who thought there was an apparent phase boundary at high temperature in α-solid solution region of the Na2MoO4-K2MoO4 binary system. The revised phase diagrams of these systems are illustrated in this article. These experimental results are in agreement with the computerized prediction using the support vector machine-atomic parameter method for the assessment of phase diagrams.     

Triode plasma nitriding and PVD coating: A successful pre-treatment combination to improve the wear resistance of DLC coatings on Ti6Al4V alloy

Diamond-like carbon (DLC) coatings have found great applicability in the automotive industry because of their low friction coefficient and high wear resistance. Nevertheless, their tribological performance can be greatly reduced on soft substrates such as titanium alloys. The hard DLC coating cannot usually follow elastic and plastic deformation of the substrate without failing. In order to overcome this property mismatch between hard coating and soft substrate, triode plasma nitriding was applied as a pre-treatment to improve the mechanical properties of the Ti6Al4V alloy and further enhance the load support for the DLC coating. DLC and multilayered TiN/DLC, CrN/DLC CrAlN/DLC coatings were deposited onto “standard” and plasma nitrided Ti6Al4V substrates. Triode plasma nitriding increased the load-bearing capacity of the coating/substrate system, as higher critical adhesion loads were recorded for DLC coatings on plasma nitrided Ti6Al4V substrates. This treatment also reduced the wear rate of the DLC coating/substrate. Further load support and lower wear rates were achieved by using TiN, CrN and CrAlN as intermediate layers on plasma nitrided Ti6Al4V substrates.     

稀土对复合处理渗层热疲劳性能的影响

进行了稀土对４Ｃｒ５ＭｏＳｉＶｌ钢硫氮碳共渗加氧化复合处理渗层热疲劳性能影响的研究结果表明，添加稀土的渗层比未添加稀土的热疲劳性能有显著提高。     

High-temperature corrosion of Ti and Ti-6Al-4V alloy

Pure titanium and Ti-6Al-4V were exposed at 750°C in an H₂/H₂O/H₂S P_{O 2}10^–18 Pa and P_{S 2}10^–1 Pa), H₂/H₂O (P_{O 2}10^–18 Pa) and air environments for up to 240 hr. The corrosion kinetics, obtained by the discontinuous gravimetric method, showed that the sulfidation/oxidation kinetics were linear for Ti and linear-parabolic for Ti-6Al-4V in the H₂/H₂O/H₂S environment. Both materials obeyed parabolic rate laws in the H₂/H₂O atmosphere after a transient period, and linear-parabolic rate laws in air. After exposure to the H₂/H₂O/H₂S atmosphere, the titanium specimen displayed a double scale of TiO₂ with an intervening TiS₂ film between the double-layered scale of TiO₂ and the substrate. Ti-6Al-4V also contained a double layer of TiO₂ together with a stratum consisting of Al₂S₃, TiS₂ and vanadium sulfide at the junction of the inner TiO₂ layer and substrate. Some Al₂O₃ precipitated in the external portion of the outer TiO₂ layer. Following oxidation in the low-P_{O 2} atmosphere a double-layered oxide of TiO₂ scale formed on both Ti and Ti-6Al-4V. The scale on Ti-6Al-4V also contained an -Al₂O₃ film situated between the outer and inner (TiO₂) layers. For both materials, multilayered-scale formation characterized air oxidation. In detail a multilayered oxide scale of TiO₂ formed on the air-oxidized Ti, while a multilayered oxide scale with alternating layers of Al₂O₃/TiO₂ developed on Ti-6Al-4V oxidized in air.     

氢对Ti—6Al—4V合金的高温增塑作用

测定了各种氢含量对Ti-6Al-4V合金的流变应力(σ),应变速率敏感指数(m)和延伸率(δ)的影响,并对其微观结构进行了观察研究。结果表明,适量的氢对该合金在800—860℃范围内具有减少流变应力和降低超塑温度以及增加塑性的作用。     

激光快速成形Ti-6Al-4V合金力学性能

采用实验研究的方法，对激光快速成形Ti-6Al-4V合金的力学性能进行了探讨。结果发现：和锻造件相比，激光快速成形沉积态Ti-6Al-4V合金的拉伸性能具有高强低塑特点和更显著的各向异性；成形试样的组织、氧含量和冶金缺陷都将影响到拉伸性能，其中组织的影响最显著，其次为氧含量和熔合不良缺陷：对于氧含量符合GJBGJB2921-1997标准的激光快速成形Ti-6Al-4V合金，经固溶时效热处理后所获得的网篮组织综合性能最好，不论是强度指标还是塑性指标都高于锻件标准。     

基于MICK-4FI资源运营模式的自制-外购决策工具开发

针对传统研究多从交易成本角度分析自制-外购决策而忽视企业内部资源动因的情况,提出了一类基于M ICK-4FI资源运营模式的自制-外购决策工具。工具主要由两个矩阵组成,分别用来分析市场需求与资源及资源与供应商间的关系。通过两矩阵中的M ICK资源将市场需求与供应商选择问题连接起来,利用专家打分法将资源和供应商选择的标准量化,再结合工具决策自制-外购问题。文中结合例子详细解释了工具的两阶段具体操作流程。企业可在变动的网络化制造环境中利用本工具进行资源自制-外购决策,因此有很高的应用价值。