回火温度对30Cr3Si2NiMoWNb钢组织性能的影响

采用扫描电镜、能谱分析和力学试验等研究了回火温度对30Cr3Si2NiMoWNb超高强度钢组织和性能的影响。结果表明,回火温度变化可实现对力学性能的大幅度调控。200~350 ℃回火,微观组织为回火马氏体与细小弥散的ε-碳化物,此阶段强韧性变化幅度较小,抗拉强度等级1700 MPa、屈服强度等级1300 MPa;350~500 ℃回火由于渗碳体的不均匀析出,强度和韧性同时下降,其中500 ℃左右回火脆性最为严重,冲击吸收能量下降至最低点;500~700 ℃回火生成较稳定的球状渗碳体,强度大幅下降,韧性大幅上升。回火温度对强韧性的影响机理为ε-碳化物、渗碳体等析出相演变过程的影响;一定含量的Si元素可以提高渗碳体形成温度和回火脆性温度。     

Effects of Cr interlayer on mechanical and tribological properties of Cr-Al-Si-N nanocomposite coating

Cr-Al-Si-N coatings were deposited on SUS 304 substrate by a hybrid coating system. A Cr interlayer was introduced between Cr-Al-Si-N coating and SUS 304 substrate to improve the coating adherence. The effects of Cr interlayer on the microhardness, adhesion, and tribological behavior of Cr-Al-Si-N coatings were systematically investigated. The results indicate that the microhardness of the Cr-Al-Si-N coatings gradually deceases with increasing thickness of Cr interlayers. The adhesion between Cr-Al-Si-N and SUS 304 substrate is improved by addition of the Cr interlayers. A peak critical load of ~50 N is observed for the coating containing Cr interlayer of 60 nm as compared ~ 20 N for the coating without Cr interlayer. The thicker Cr interlayers result in reduced critical load values. Moreover, the wear resistance of the Cr-Al-Si-N coatings is greatly enhanced by introducing the Cr interlayer with thickness of 60 nm in spite of the decreased microhardness. The friction coefficient of the coating system is also moderately reduced.     

A study of the Zn-Rich corner of the Zn-Fe-Sn system

The Zn-rich corner of the 450 °C isothermal section of the Zn-Fe-Sn system was experimentally determined. Within the composition range explored in this study, the liquid phase was found in equilibrium with the ternary extensions of three binary Zn-Fe phases, the ζ, δ, and Γ₁ phases. The ζ phase contains practically no Sn in solid solution; Sn solubility limits in the δ and Γ₁ phases were 2.2 at.% and 7.0 at.%, respectively. The only Fe-Sn compound detected in this study was FeSn, which co-existed with the Γ₁ phase. When its Sn content was lower than approximately 26 at.%, the liquid solidified in water quenching as a degenerated eutectic consisting of a mixture of η-Zn and β-Sn co-existing with primary ζ crystallites. When its Sn content exceeded approximately 70 at.%, the liquid transformed into metallic glass containing mostly Sn, Zn, and a small amount of Fe upon water quenching from 450 °C.     

低温回火对Cu-18A1-10Mn(at%)合金形状记忆性能的影响

利用电阻法、光学显微观察和X射线衍射等方法研究了低温回火对Cu-18Al-10Mn(a%)合金形状记忆性能的影响.结果表明:合金在淬火态伪弹性占支配地位,随回火温度升高伪弹性逐渐减弱而形状记忆效应占支配地位.其原因是低温回火使得过饱和淬火空位浓度降低、对母相的钉扎作用减弱、有利于母相向马氏体相转变所致.     

行波磁场发生器上磁场分布及其熔体充型特征

利用ANSYS软件，计算了行波磁场发生器上方的磁场变化规律，并与试验检测结果进行了对比，两者结果吻合较好。发现了与行波磁场极距相关的临界熔体长度现象，当熔体长度小于临界长度时，行波磁场对熔体的运动不产生影响，该临界长度与极距有关。金属熔体在行波磁场铸造充型过程中受到6个力的作用，这6个力共同作用的结果使熔体充型过程中速度的变化存在加速、匀速、减速的变化规律，解释了与此相对应的铸造缺陷如冷隔、浇不足等形成的原因，并提出了两种改变磁场分布的方法。ANSYS计算结果表明，用这两种方法可以实现递减分布的磁场。     

多元复合化学镀层构造理论及其应用

提出了多元复合化学镀层的微观构成原理,揭示了复合化学镀层的微观结构与宏观性能的关系,分析了影响镀层微观结构的主要因素如分散相颗粒的尺寸、搅拌方式、镀液中分散相粒子的含量等,为多元复合化学镀的配方和工艺设计提供了重要的理论依据.     

热挤压工艺对690合金组织的影响及控制

利用Gleeble热压缩实验,构建了690合金的挤压工艺的再结晶图,探讨了完全动态再结晶的临界挤压工艺,将合金的热变形组织演变模型带入deform-2D有限元软件,并针对挤压中合金的组织演变过程对有限元软件进行了二次开发,进而模拟计算了挤压比、坯料温度以及挤压速率对690合金挤压管组织的影响规律,依据挤压机设备能力以及组织要求提出了挤压工艺的控制方法,并进一步根据有限元计算结果进行实际挤压验证。结果表明：挤压管的晶粒尺寸随着挤压比的增大呈现出先降低后增加的趋势;690合金挤压管的晶粒尺寸随坯料温度和挤压速度的降低而减小;当坯料温度在1200℃,挤压比为15.3,挤压速率200 mm/s时,挤压管的晶粒尺寸可以控制在62.7 μm以下;模拟计算结果与挤压管的相对误差仅为4.5%。     

半固态铸造的现状及发展前景

论述了半固态铸造技术的基础理论研究 (半固态合金流变行为及其微观组织特征 )、半固态铸造合金成形过程的数值模拟、半固态铸造原材料的制备工艺、性能及工业应用现状。介绍了已有的研究工作 ,并提出了我国在这一领域的发展方向     

Microstructures of Sintered Mo-Cu Alloys with Mechanically Activated Powder

Mo-Cu alloy has been investigated for manyyears due to its excellellt properties such as electrical and thermal conductivity. Higher requirements are needed to enable the developmellt ofelectronic devices and semiconductor with greatpower and better properties [l], such as electrical and thermal conductivity, strength, hardness,especially linear eXPansion coefficiellt and gasproofproperty.The synthesis of adVanced Mo-Cu alloy requires new process. Melting is a classic method.For Mo-Cu allo…     

反井技术在罗河铁矿的应用

马钢罗河铁矿一期井巷开拓工程中,连接井下-455m采区水平和-560m水平主运输巷道之间的阶段竖井采用反井钻机进行施工,获得了成功的技术经验,并成功贯通成井三条,与传统的凿井方法相比具有相当大的优势。