轧制参数对含钒、氮的低合金高强度钢沉淀强化的影响

本文研究了形变热处理工艺对低氮和高氮的含钒低合金高强度钢的沉淀强化的影响。研究指出为了达到最大的沉淀强化效果,应该防止在奥氏体内出現形变诱发沉淀。氮化钒的形变诱发强化在900～950℃非常迅速地产生,但是碳化钒则在830～85℃的较低的轧制温度下产生形变诱发强化。已经考察了重新加热温度、轧制压下量、保温温度和时间的影响。业已表明沉淀强化程度约在化学当量比(V/C)处最大,但是在这个比值下,奥氏体中形变诱发强化也非常显著。氮化钒在奥氏体中沉淀有损于在铁素体中沉淀强化。但若能防止氮化钒在奥氏体中的沉淀,那么增加钢中含氮量可增加沉淀强化并能获得较高的屈服强度。铌表现出非常有效的細化晶粒作用虽然在适当的情况下它与钒比较能在更大程度上产生显著的沉淀强化,特别是在相同的低含量时。然而Nbc在奥氏体中很易形变诱发为沉淀,随后有损于铁素体的沉淀强化。另一方面钒很易于通过氮化钒而用以细化晶粒并且利用碳化钒产生沉淀强化。     

沉淀强化型因瓦合金研究概况

简要对比了因瓦合金细晶强化、固溶强化、加工硬化与沉淀强化等4种强化机制,总结了沉淀强化型因瓦合金的研究现状,并对高强度因瓦合金的发展提出了展望。      

强化液相沉淀微观混合制备药物纳微颗粒

采用反溶剂和反应沉淀方法,利用微通道反应器和超重力反应器强化液相沉淀微观混合,制备模型药物枸橼酸喷托维林纳微颗粒并分析颗粒性质。结果表明:新型反应器能够通过强化液相沉淀微观混合制备得到药物纳微颗粒,颗粒为片状结晶,粒径在100~200 nm,制备过程中药物微观物相结构未发生改变;其中反溶剂沉淀为快速物理过程,适于强化微观混合,超重力反应器具有最高的制备效率。     

沉淀强化高熵合金研究进展

高熵合金是一类由多种主要元素共同组成的新型金属材料,其具有独特的微观结构和可调性能,在国内外已获得广泛关注。沉淀强化被证明是提高高熵合金屈服强度的一种非常有效的手段,并且沉淀相和基体之间的共格界面对于实现强度和塑性的良好结合非常重要。合理控制沉淀相的类型、形状、大小和体积分数是提高合金强塑性的关键因素。研究证实,采用不同的轧制、退火和时效等热处理工艺可调控合金的基体微观组织、沉淀相特征。沉淀强化高熵合金虽然表现出优异的拉伸性能和热稳定性,但目前对其疲劳、蠕变和氧化行为及相关机理等尚不清晰。因此,应对材料进行综合评价以促进性能优越的高温器件的合理设计和制造。使用计算模拟的方式对沉淀相的元素分布、电子结构、成键状态等内在特性进行量化研究,对沉淀相的演化过程进行针对性的预测和控制,有助于合理设计合金成分体系。本文综述了沉淀强化高熵合金的相形成、力学性能、热稳定性和计算机建模等方面的研究进展,归纳总结了相关问题,对今后设计沉淀强化高熵合金具有一定的指导意义。     

强化机制对钢的冷脆特性的影响

本文研究了在沉淀强化和细晶强化两种机制分别作用的处理条件下低碳钢系列温度断裂行为阐明了不同强化机制对钢件塑一脆转变特性的影响。结果表明,沉淀强化不影响材料解理特征应力 S_(c0),钢的冷脆特征温度 T~*_c 增高系由屈服极限σμ的提高引起。而在细晶强化条件下σ_y和 S_(c0)均得到提高且后者提高的幅度大于前者,故使 T~*_c 降低。     

Mg-Zn系合金沉淀硬化研究进展

Mg-Zn系合金因具有显著的沉淀硬化效果,成为最具发展前景的结构材料之一。通过微合金化调控沉淀相行为、增加沉淀密度并减少颗粒间距,可进一步增强其沉淀硬化效果。微合金化元素可分为稀土、碱土以及其他元素,其中稀土元素可使沉淀相密度增加,碱土元素不仅能增加沉淀相密度,还能细化第二相,其他微合金化元素可在时效过程中提高沉淀相形核率,并加速沉淀过程。本文综述了Mg-Zn系合金沉淀行为的析出热力学以及析出序列的研究进展,归纳了微合金化元素对沉淀强化的作用,展望了Mg-Zn沉淀镁合金领域今后的研究方向。     

ZG1Cr10MoWVNbN耐热钢的断裂特征与强化机制

采用金相、SEM和TEM等方法对耐热钢ZG1Cr10MoWVNbN进行了组织分析,利用断口分析方法对该材料的断裂特征进行了分析,并对材料的强化机制进行了研究,结果表明:材料的组织为板条状马氏体,该马氏体中含有大量的高密度位错和亚结构,在该组织中弥散分布着碳化物、氮化物以及碳氮化物颗粒状析出物;试样的断口为准解理断口,该材料在具有较高强度的同时也具有一定的韧性;材料的强化机制包括马氏体相强化、固溶强化、碳化物颗粒沉淀强化、氮化物和碳氮化物颗粒沉淀强化.     

微钛低碳钢板的微观组织观察与分析

利用金相显微镜和电子显微镜等方法对微Ｔｉ低碳钢板的微观组织和第二相粒子的沉淀行为进行了研究。结果表明，基体组织由极细晶铁素体和亚晶粒组成，铁素体晶粒平均尺寸为４．８７μｍ。细小的第二相粒子在铁素体中沉淀析出，粒子的平均尺寸为１２．４ｎｍ，沉淀的粒子体积百分数为０．０３６％。在亚晶界上观察到大粒子的沉淀，位错被细小呈球形的粒子所钉扎．相分析表明，这些粒子为ＴｉＮ，Ｔｉ（Ｃ、Ｎ）或ＴｉＣ．经计算，沉淀强化与细晶强化值分别为４０ＭＰａ和２４０ＭＰａ。     

时效对SiCw／Al—Li—Cu—Mg—Zr复合材料组织和性能的影响

对挤压铸造法制备的ＳｉＣｗ／Ａｌ－Ｌｉ－Ｃｕ－Ｍｇ－Ｚｒ复合材料经１９０℃时效不同时间的微观组织和性能进行了研究，结果表明，复合材料在该时效温度下的主要沉淀强化相为δ′相，第二强化相为Ｓ′相，复合材料中的高密度位错促进了δ′相的长大和Ｓ′相的沉淀析出过程，时效对复合人有明显的强化作用，而对复合材料拉伸断口的影响甚微。     

稀土镁合金沉淀析出行为研究进展

概述了稀土镁合金(Mg-RE)沉淀析出行为的研究进展。根据析出序列的不同将稀土镁合金分为Mg-Gd、Mg-Y、Mg-Nd及Mg-MM四种类型,对不同类型Mg-RE的沉淀析出序列及析出相的形貌、晶体学特征参数、转变动力学机制和沉淀强化行为做了较为详尽的综述。此外还指出了Mg-RE沉淀析出行为研究中存在的不足,并展望了其发展前景及今后的研究方向。     

微合金化3.5Ni钢的强化机理

从固溶强化、析出强化和细晶强化三个方面对微合金化 3.5Ni 钢的强化机理进行了分析研究,同时计算了三种强化方式对强度的贡献.结果表明:3.5Ni 钢进行 Nb,Ti微合金化后,通过适当的工艺控制,钢中可以析出较多均匀细小的 Nb(C,N),NbTi(C,N) 球形颗粒和 TiN 方形颗粒.这些细小粒子一方面产生析出强化的效果;另一方面钉扎奥氏体晶界,阻止晶粒长大,从而产生强烈的细晶强化效果.强度的理论计算值和实测值非常接近,同时,与国家标准 CCS1996 <钢质海船入级与建造规范>中的要求相比,有超过 20% 的余量.     

Microstructure and strength modelling of Al–Cu–Mg alloys during non-isothermal treatments: Part 1 – Controlled heating and cooling

Abstract

A model is developed to predict the precipitation kinetics and strengthening in Al–Cu–Mg alloys during non-isothermal treatments consisting of controlled heating and cooling. The prediction of the precipitation kinetics is based on the Kampmann and Wagner model. The precipitation strengthening by the shearable Cu–Mg co-clusters is modelled on the basis of the modulus strengthening mechanism and the strengthening by the non-shearable S phase precipitates is based on the Orowan looping mechanism. The model predictions are verified by comparing with hardness, transmission electron microscopy and differential scanning calorimetry data on 2024-T351 aluminium alloys. The microstructural development and strength predictions of the model are generally in close agreement with the experimental data.     

The effect of deformation-induced-ferrite-transformation on nanometre-sized carbides in Ti–Mo ferritic steel

In this study, the effect of deformation-induced-ferrite-transformation (DIFT) rolling on precipitation in Ti–Mo ferrite matrix micro-alloyed steel was investigated by comparing to rolling in austenite non-recrystallisation region. The precipitate volume fraction and precipitation-starting time-temperature (PTT) curves under two kinds of process were calculated by thermodynamic and kinetic calculation, and the effects of non-recrystallisation rolling and DIFT rolling on the contribution of strengthening mechanisms were quantitatively analysed. The results showed that comparing with rolling in the austenite non-recrystallisation region, carbides in the steel by DIFT rolling were finer and more uniform. Moreover, DIFT rolling could enhance fine grain strengthening and precipitation strengthening simultaneously, and the increments of fine grain and precipitation strengthening were 34 and 63.7?MPa, respectively.     

Fe-Al金属间化合物材料的强化机理及其高温性能研究现状

对Fe-Al金属间化合物的高温力学性能和抗氧化性能的研究现状进行了回顾.归纳和描述了固溶强化、析出强化、有序强化、弥散强化等强化机理以及Fe-Al材料抗氧化的机理.并对Fe-Al材料研究的发展进行了展望.     

Critical Assessment 9: Wrought magnesium alloys

This assessment is focussed on wrought magnesium alloys for lightweight applications, particularly in the transport sector. The challenges to their wider use are summarised, including poor low temperature formability, corrosion issues, dissimilar metal joining, and limited precipitation strengthening. The fundamental origins of these challenges, and current research to address them, are highlighted. Key developments such as the use of dilute rare earth additions to manipulate texture for improved formability are discussed. Opportunities to exploit the unique properties of wrought magnesium alloys where further research is required are identified.     

Microstructure characterizations and strengthening mechanism of multi-principal component AlCoCrFeNiTi0.5 solid solution alloy with excellent mechanical properties

It was reported that AlCoCrFeNiTi_0.5 alloy exhibits excellent comprehensive mechanical properties. In this letter, this alloy was further studied on its microstructures and strengthening mechanism. The super-high strength and good plasticity of AlCoCrFeNiTi_0.5 alloy should be attributed to its microstructure of intrinsic strong body-centered cubic solid solution, and effective multiple strengthening mechanisms like solid solution strengthening, precipitation strengthening, and nano-composite strengthening effects, etc.     

Joint effect of quasicrystalline icosahedral and L12-strucutred phases precipitation on the grain structure and mechanical properties of aluminum-based alloys

Dispersoid hardening is a key factor in increasing the recrystallization resistance and mechanical strength of non-heat treatable aluminum-based alloys.Mn and Zr are the main elements that form dispersoids in commercial Al-based alloys.In this work,the annealing-induced precipitation behavior,the grain struc-ture,and the mechanical properties of Al-3.0Mg-1.1 Mn and Al-3.0Mg-1.1 Mn-0.25 Zr alloys were studied.The microstructure and the mechanical properties were significantly affected by annealing regimes after casting for both alloys.The research demonstrated a possibility to form high-density distributed quasicrystalline-structured I-phase precipitates with a mean size of 29 nm during low-temperature annealing of as-cast alloys.Fine manganese-bearing precipitates of Ⅰ-phase increased recrystallization resistance and significantly enhanced the mechanical strength of the alloys studied.The estimated strengthening effect owing to Ⅰ-phase precipitation was 150 MPa.Due to the formation of L12-structured Al3Zr dispersoids with a mean size of 5.7 nm,additional alloying with Zr increased yield strength by about 90 MPa.The L12-phase strengthening effect was estimated through the dislocation bypass looping and shearing mechanisms.     

金属材料的抗蠕变机理及方法综述

本文分析了传统金属材料抗蠕变性能的不足以及研制抗蠕变性能优良的金属材料的必要性。通过分析影响蠕变的因素,得出蠕变温度和蠕变应力能够影响蠕变行为,而析出相又是影响蠕变行为的关键因素这一结论。综述了固溶强化、析出强化、弥散强化和晶界强化等几种提高材料抗蠕变性能的方法及机理,列举了几种常见的蠕变试验方法。最后展望了抗蠕变金属材料广泛的应用前景。     

Precipitation behavior and strengthening effect in thermomechanical treatments of Al‐Zn‐Mg alloys

Abstract

An investigation was carried out to determine the precipitation behavior and strengthening effect in various thermomechanical treatments of Al‐Zn‐Mg alloys containing high Zn and low Mg contents. The results show that the precipitation behavior is largely influenced by a plastic deformation in the thermomechanical treatment, and the final precipitate and dislocation structures are greatly related to the influenced precipitation behavior; hence the strengthening effect is determined. Different alloy contents also cause different influences. A super‐strengthening occurs in the T‐AHA (80°C) treatment attributed to the optimum combination of dislocation and precipitate structure.     

超高强度船体结构钢的开发现状与趋势

为了给超超高强度船体结构钢的开发提供理论指导,从性能要求、强韧化机制和焊接性几个方面综述了超高强度船体结构钢的特征,结合国内外超高强度船体结构钢的开发现状,阐述了强化机制的调整是超高强度船体结构钢总体的发展趋势,其中以析出强化的增加为主要特点.通过分析各种析出强化粒子的引入在高强钢中的作用特点,认为综合考虑析出粒子的引入带来的细晶优化效果、组织转变优化效果与析出强化效果对韧性的影响是超高强度船体结构钢开发的技术难点之一,同时保持良好的焊接性是超高强度船体结构钢开发的另一技术难点.