利用最小晶格错配和强有序效应发展超强金属材料（英文）

本文概括总结了传统超高强度钢的强韧化机制,针对2 GPa以上超高强度钢强韧性匹配不足、成本昂贵等突出问题,提出了最小化晶格错配和强有序效应以发展新型超强金属材料,并协同利用高密度共格粒子、高密度位错、弹性畸变中心等多重效应,克服传统共格析出强化合金低塑韧性问题,实现超高强度钢良好强韧性匹配.     

Al-Zn-Mg-Cu系超高强度铝合金的研究进展

Al-Zn-Mg-Cu系超高强度铝合金具有低密度、高比强度、高韧性和良好的抗腐蚀性能的特点,广泛应用于航空航天、交通运输和兵器领域。本文主要介绍近年来国内外Al-Zn-Mg-Cu系超高强度铝合金的最新研究进展。超高强度铝合金基体上分布着纳米级的晶内时效析出相、亚微米级的高温析出相、微米级的结晶析出相和晶界析出相,这些相的形态、数量、尺寸和分布对合金的综合力学性能和抗腐蚀性能有直接的影响;主元素成分含量对超高强度铝合金综合力学性能有影响,合金的综合力学性能随Zn/Mg和Cu/Mg比值的变化而变化;微量元素能够提高超高强度铝合金的综合力学性能。微量元素对铝合金的影响主要体现在提高沉淀相的过饱和度,改变沉淀析出过程,促进或抑制沉淀相的析出和促进新相的沉淀析出。新制备技术能够显著细化晶粒、抑制偏析、析出相均匀分布和提高各种元素的过饱和度,从而改善超高强度铝合金的综合力学性能。强化固溶处理能够提高时效析出程度,从而提高铝合金的力学性能。三级时效处理后的超高强度铝合金具有峰值时效T6态的强度和优异的抗腐蚀性能。     

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.     

高强度低合金钢(HSLA)的研究进展

高强度低合金钢是在普通碳素钢基础上发展起来的,由于其强度适中、加工性好且经济适用而在汽车、船舶与海洋工程以及桥梁等基础设施建设方面得到了广泛的应用。由于对钢材性能要求的不断提高,尤其是焊接性能和低温韧性,因此铜沉淀强化高强度低合金钢受到极大的重视而迅速发展起来。首先介绍了高强度低合金钢的发展历程,结合强化机制重点介绍了双相高强度低合金钢和含铜高强度低合金钢的开发思想,并对高强度低合金钢的基体相显微结构控制和强化方式进行了评述;随后对等温冷却和连续冷却过程中高强度低合金钢的相变尤其是铜沉淀相的析出过程进行了介绍;最后介绍了富铜纳米相的概念以及表征纳米相的方法,评述了合金元素对富铜纳米相形成的影响。     

超快冷对碳素钢中渗碳体析出强化行为的影响*

用超快速冷却技术并控制轧后冷却温度, 研究了3种碳含量不同的碳素钢热轧后组织中渗碳体的析出行为和强化机制。结果表明, 在超快速冷却条件下0.04%C和0.5%C(质量分数, 下同)实验钢的主要强化方式分别是细化晶粒和细化珠光体片层间距, 没有纳米级渗碳体颗粒析出, 而在0.17%C实验钢的组织中则有大量弥散的纳米级渗碳体析出, 颗粒直径范围为10-100 nm, 通过超快速冷却技术实现了在不添加微合金元素的条件下纳米级渗碳体的析出。随着超快速冷却终冷温度的降低纳米渗碳体的析出强化作用使0.17%C钢的屈服强度提高110 MPa, 强化效果明显。在超快速冷却的工艺基础上若继续采用形变热处理工艺, 可进一步提高0.17%C实验钢的位错密度, 促进渗碳体均匀形核, 实现纳米级渗碳体颗粒在整个组织中更加均匀弥散的分布, 达到更好的均匀强化效果。在超快速冷却和形变热处理工艺条件下0.17%C钢的屈服强度可达到650 MPa以上, 强化效果提高300 MPa以上。     

飞机起落架用超高强度不锈钢的研究及应用进展

本文结合飞机起落架的设计理念,梳理了飞机起落架用超高强度钢及高强不锈钢的应用及发展历程,重点阐述了典型超高强度不锈钢的成分、组织和力学性能以及强韧化机理。建议通过材料热力学动力学计算创新设计新的超高强度不锈钢钢种;提出新型超高强度不锈钢的组织设计,将更关注多类型或高密度的共格析出强化以及高力学稳定性残余奥氏体的强韧化作用机制;最后指出采用最新的一些加工工艺技术,如等温多向锻造工艺技术,可显著提高超高强度不锈钢的综合力学性能。     

热轧双相钢的发展现状及高强热轧双相钢的开发

介绍了热轧双相钢的发展现状及存在问题,指出低成本热轧双相钢、高延伸凸缘型铁素体+贝氏体热轧双相钢(F-B热轧双相钢)及高强度热轧双相钢的开发及应用,将促进我国热轧双相钢的发展,推动汽车工业的"以热代冷"进程。同时,探讨了纳米析出强化型热轧双相钢的强化机理及工艺控制原理,并在实验室进行了中试,开发出铁素体基体析出强化型的热轧双相钢,其抗拉强度达770~830 MPa,屈强比0.75,组织为铁素体+马氏体,且铁素体基体中存在大量细小的纳米级尺寸的TiC过饱和析出和相间析出。     

基于S35140钢的超低碳成分设计和力学性能研究

S35140钢是一种基于25Ni-20Cr的奥氏体耐热钢,为了获得高强度,通常会提高碳含量,但碳含量较高不利于高温时效稳定性和长期耐腐蚀性能.本文在S35140钢的基础上,大幅度降低碳含量,并通过调控N和Nb等微合金元素含量,以及加入Ti元素,促使析出新的强化相,弥补减少碳含量所导致的强度降低.同时引入一定量的Al元素...     

一种新型高强度钢—低含金TRIP钢

前言 在目前大量研究与应用的固溶强化、弥散析出强化,加工强化及组织强化等几种类型的高强度钢中,双相钢的强度高,同时塑性也较好,双相钢的强度取决于马氏体的数量与形态,如果双相钢的强度极限(σ_0)800MPa,马氏体的含量大约30％以上,此时钢的塑性较差,以冷轧薄钢板为例,当σ_b=80OMPa时,拉伸延伸率δ大约20％,当σ_b=1000MPa时,δ则只有15％。为了发展强度极限在800MPa上,而塑性也较好的钢种,国外近几年研制一种含有较多残留奥氏体的新型高强度钢—低含金TRIP钢。 在钢的Ms—Md温度范围内,应变诱发马氏体相变,此时钢呈现较高塑性,称为相变诱导塑性(Transformationinduced plasticity)。V.F.Zackay教授首先利用此效应研制高强度、高塑性的合金并命名为TRIP钢,但由于合金元素含量高,外理工艺复杂,一直没有工业应用。残留奥氏体也具有TRIP效应,也可利用残留奥氏体的TRIP效应发展高强度、高塑性钢。为了与V.F.Zackay等人研究的高合金化的TRIP钢相区别,我们称此种含有残留奥氏体高强度低合金钢为低合金TRIP钢。该钢目前主要     

低合金及微合金高强度钢

本文论述第三世界国家发展低合金及微合金高强度钢方面的优势及应注意事项,利用少量或微量合金元素控制轧制、控制冷却工艺,取代昂贵的进口热处理合金钢,发挥现有设备的潜力,节约基建投资。铌不仅通过细化晶粒,而且也通过析出相使强度韧性都得到提高;钒主要通过析出强化提高强度,与铌相比,钒的品粒细化作用较小,因而随着强度的提高缺口冲击试样的脆性转变温度随之增高;钛的细化晶粒作用和析出强化作用都较小,只有在较高的含量下才会起到抑制再结晶的作用,但钛可以控制硫化物的形态。这些合金元素的特点被用来改进控制轧制和控制冷却,从而发展出更经济合理的RCR(再结晶控制轧制)和OLAC(在线加速冷却)生产工艺。     

New developments in carbon and alloy steels

Recent developments in carbon and alloy steels outlined in this paper include those pertaining to low-carbon mild steels, high-strength low-alloy (HSLA) steels, dual-phase steels, low-carbon bainitic steels, ultrahigh strength steels and ferritic stainless steels. The factors that improve the cold-forming characteristics of low carbon sheets and strips are outlined. The physical metallurgy principles governing the ferrite grain refinement in HSLA steels are discussed, pointing out how it can be achieved by the controlled rolling process. The importance of sulphide shape control in imparting the necessary through-thickness ductility in HSLA steels is discussed and the various methods available for inclusion shape control are outlined. Improved formability coupled with adequate strength characterizes the dualphase steels. Among the ultrahigh strength steels, two recent developments,viz. TRIP steels and maraging steels are outlined. It is pointed out how the improved formability of ferritic stainless steels is making them compete with the more expensive austenitic stainless steels. The scope for future developments in these steels is discussed at the end.     

Zum Einfluss des Schweißens auf das Kriechverhalten moderner Stähle für die thermische Energieerzeugung

The influence of welding on creep behaviour of modern steels for thermal power generation Un‐ and low alloyed ferritic/bainitic Chromium steels as well as high alloyed ferritic/martensitic 9–12 % Chromium steels are widely used for high temperature components in thermal power generation. Welding in all its variety is the major repair and joining technology for such components. The weld thermal cycle has significant influence on the base material microstructure and its properties. The Heat Affected Zone is often regarded as the weakest link during high temperature service. While weldments of un‐ and low alloyed ferritic Chromium steels can show significant susceptibility to Reheat Cracking in the coarse grained heat affected zone, weldments of high alloyed ferritic Chromium steels generally fail by Type IV Cracking in the fine grained heat affected zone during long term service. In this paper the influence of the weld thermal cycle on the base material microstructure is described. Long‐term creep behaviour of weldments is directly related to the main failure mechanisms in creep exposed ferritic weldments and implications for industries using heat resistant ferritic steels are shown.     

Mechanisch-technologische Eigenschaften nickelhaltiger Superferrite

Mechanical and Technological Properties of Nickel Containing Superferrites High chromium ferritic stainless steels with molybdenum and nickel additions, containing low amounts of interstitials, show remarkably good mechanical properties besides their excellent corrosion behaviour. Yield strengths of these materials can be more than the twofold, compared with that of austenitic stainless steels. In contrary to commercial ferritic stainless chromium steels, the Superferrites exhibit remarkable notch impact toughness also at temperatures below 0 °C. These properties as well as their permanent toughness after a welding process permit a good technological workability and, because of the high strength properties, the application of thinner dimensions in construction.     

薄板坯连铸连轧低成本高性能微合金化钢的研发进展

近年,薄板坯连铸连轧这一崭新的钢铁短流程生产线在我国得到迅速发展,目前在生产线数量、产能以及年产量等方面中国都位居世界前列,并在薄板坯连铸连轧的工艺特征和组织性能控制机理研究等方面开展了大量工作.简要说明了薄板坯连铸连轧工艺的冶金材料学特征,综述了近年我国在利用薄板坯连铸连轧工艺进行低成本高性能微合金化钢的研发方面的进展,重点介绍了薄板坯连铸连轧研究开发的微合金化高强和超高强耐候钢、工程机械用低碳贝氏体超高强钢、高强汽车结构用钢、冷冲压用钢和高性能管线钢等微合金化板带产品的成分、组织和性能.     

高合金超高强度钢的发展

超高强度钢是在普通合金结构钢的基础上发展起来的一种超高强度、高韧性合金钢,在现代工业中占有重要地位,在航空、航天部门也被广泛使用.本文介绍了超高强度钢,特别是高合金超高强度钢的发展和应用情况,指出了现今在这一领域的研究热点.     

High strength-superplasticity combination of ultrafine-grained ferritic steel:The significant role of nanoscale carbides

There is currently a gap in our understanding of mechanisms that contribute to high strength and high plasticity in high strength UFG ferritic steel with nano-size Fe3C carbides in situations that involve com-bination of various strain rates and high temperature.In this regard,we describe the mechanistic basis of obtaining high strength-high plasticity combination in an ultrafine-grained(UFG)(～500±30 nm)ferritic steel with nano-size carbides,which sustained large plastic deformation,exceeding 100％elon-gation at a temperature significantly below 0.5 of the absolute melting point(Tm).To address the missing gap in our knowledge,we conducted a series of experiments involving combination of strain rate and temperature effects in conjunction with electron microscopy and atom probe tomography(APT).Strain rate studies were carried out at strain rates in the range of 0.0017-0.17 s-1 and at different temperatures from 25℃to 600℃.Dynamic recrystallization occurred at 600℃,resulting in a significant decrease in yield and tensile strength.Nevertheless,the UFG ferritic steels had an advantage in tensile strength(σUTS)and elongation-to-failure(εf)at 600℃,especially at strain rate of 0.0017 s-1,with high σUTS of 510 MPa and excellent low temperature(＜0.42Tm)superplasticity(εf=110％).These mechanical properties are significantly superior compared to similar type of steels at identical temperature.A mechanistic under-standing of mechanical behavior of UFG ferritic steels is presented by combining the effect of strain rate,temperature,and nano-size carbides.     

Brittle fracture of high-strength steels at very low temperatures

High-strength steels are used to increase the load carrying capacity of components. However, to guarantee a safe design, it is also necessary to combine high strength with adequate fracture toughness. In this paper, fracture toughness of three high-strength steels with yield strengths ranging from 460 to 890 MPa has been studied at very low temperatures. Taking into account experimental evidence, a new mechanism of cleavage at very low temperatures is proposed. This mechanism considers the possibility of reaching the ideal strength (the stress at which the lattice of a single crystal losses its stability) in the immediate vicinity of the fatigue crack tip. Moreover, a computational model able to calculate the external load needed to produce a catastrophic failure of these steels has been developed.     

Prevention of the overestimation of long-term creep rupture life by multiregion analysis in strength enhanced high Cr ferritic steels

Long-term creep rupture life is often evaluated from short-term data by a time–temperature parameter (TTP) method. However the conventional TTP methods sometimes fail in understanding creep rupture behavior of strength enhanced high Cr ferritic steels and overestimate creep rupture life in long-term creep. In the present paper, creep rupture data of seven kinds of heat resistant steels with different W and Cr concentrations have been analyzed. The conventional TTP method like Orr–Sherby–Dorn analysis evaluates long-term creep rupture life assuming a unique value of activation energy for all the creep rupture data. This analysis is called single region analysis in this paper. The single region analysis can represent well the creep rupture data of steels containing less than 8% Cr. The creep rupture analyses of steels containing more than 8% Cr exhibit that apparent activation energy changes from a high value in short-term creep region to a low value in long-term creep region. In each case a creep data was divided into several data sets, and then the conventional single region analysis was applied to each divided data set. This analysis is referred to as multiregion analysis. The multiregion analysis describes very well all the data points, whereas regression curves of the single region analysis deviate from the data points, resulting in overestimation of long-term rupture life. The difference between the two activation energies of short-term and long-term creep increases with increasing Cr concentration. Therefore, the overestimation due to singles region analysis is expected to be more serious at higher Cr concentration.     

Effect of microstructure on cleavage resistance of high-strength quenched and tempered steels

The relationship between microstructure and cleavage resistance in quenched and tempered high-strength bainitic and martensitic steels is investigated by means of Charpy-V tests, uniaxial tensile test on unnotched specimens and electron back scattered diffraction (EBSD). Steels under investigation are low/medium carbon (C = 0.10-0.40%) steels with yield strength in the range YS = 500-1000 MPa.Results show that the tensile strength and the cleavage resistance of quenched and tempered (Q&T) steels appear to be controlled by different structural parameters and not, as in the case of polygonal ferritic steels, by the same structural unit. In particular, yield strength is controlled by the mean subgrain size, whereas the structural unit controlling the critical cleavage stress is the covariant (bainitic or martensitic) packet, whose size is slightly lower than the average unit crack path (UCP). The critical stage in the fracture process appears to be the propagation of a Griffith crack from one packet to another, and the resistance offered by high-angle boundaries is approximately the same as that of low-C steels with bainitic or polygonal ferrite microstructure.