Strong and ductile Mg alloys developed by dislocation engineering

Dislocation engineering concept has been successfully employed to tackle the strength-ductility trade-off in steels, resulting in the development of high-strength high-ductility deformed and partitioned (D&P) steel. The present perspective proposes to employ such dislocation engineering concept to develop strong and ductile magnesium (Mg) alloys. High density of?<?c?+?a?>?dislocations could be generated at appropriate temperature and retained in the Mg alloy after quenching to room temperature. Those?<?c?+?a?>?dislocations inherited from the warm deformation could provide?<?c?+?a?>?dislocation sources when the Mg alloy is deformed at room temperature, resulting in good ductility. The high dislocation density generated at warm deformation provides dislocation forest hardening, leading to improved yield strength of Mg alloy.     

Stabilisation of ferrite in hot rolled δ-TRIP steel

Abstract

A steel has recently been designed to benefit from the deformation induced transformation of retained austenite present in association with bainitic ferrite. It has as its major microstructural component, dendrites of δ-ferrite introduced during solidification. The δ-ferrite replaces the allotriomorphic ferrite present in conventional alloys of this kind. The authors examine here the stability of this δ-ferrite during heating into a temperature range typical of hot rolling conditions. It is found that contrary to expectations from calculated phase diagrams, the steel becomes fully austenitic under these conditions and that a better balance of ferrite promoting solutes is necessary in order to stabilise the dendritic structure. New alloys are designed for this purpose and are found suitable for hot rolling in the two-phase field over the temperature range 900–1200°C.     

Alloy design with the aid of molecular orbital method

A molecular orbital approach to alloy design has recently made great progress. This is applicable not only to structural alloys, but also to functional alloys. In this paper we have focussed on two materials as examples: high Cr ferritic steels and hydrogen storage alloys.     

Q&P热处理工艺对含Cu TRIP钢组织和性能的影响

随着能源的短缺和环境污染的日益严重,汽车轻量化需求日益迫切,如何通过工艺及成分设计革新、获得兼具高强度和高塑性的钢板尤为重要.尝试将Cu作为合金元素加入TRIP钢中,采用淬火配分(QP)工艺对含Cu TRIP钢进行一步法和两步法热处理,通过拉伸试验、X射线衍射分析、扫描电镜、透射电镜等实验手段,对热处理后的组织及性能进行测试和观察,探究了不同热处理工艺对组织和性能的影响.研究结果表明:一步法处理后的显微组织为铁素体、马氏体和残余奥氏体,两步法处理后不仅包含上述3种组织,还含有贝氏体.一步法处理后,抗拉强度达2 200 MPa,拉伸延展率为15%,强塑积为33 GPa·%;两步法处理后综合力学性能优于一步法,在400℃等温5 min后,抗拉强度为1 300 MPa,拉伸延展率为43%,强塑积超过55 GPa·%.实验钢良好的综合力学性能得益于铁素体、马氏体/贝氏体和残余奥氏体的合理配比,变形过程中残余奥氏体的相变诱导塑性效应,以及马氏体位错与Cu粒子的交互作用.     

Process control maps to design an ultra-high strength-ductile steel

Steel with 2.4–2.5 GPa tensile strength and elongation to fracture of 4.8–5.7%, is produced by designing a novel heat treatment identical to quenching and tempering, in less than a few minutes. Since addition of Si to Fe–Mn steel promotes the austenite stabilisation by carbon enrichment, the elongation to fracture of 0.6C–1.6Si–1.2Mn (wt-%) steel treated by different quenching and partitioning (Q&P) routes is improved. Results demonstrated by process control maps give a good overview of the final microconstituents. By using higher partitioning temperatures, the tempering of martensite, stabilisation of austenite and improvement of the mechanical properties, could effectively be accelerated. This approach results in significant time and cost reduction which makes this heat treatment attractive for industries.     

Generic research for design of made-to-order engineering products

The paper identifies those design research issues which, while being of particular interest to the made-to-order (MTO) sector, have a wide applicability. An overview of the Newcastle EDC research programme is provided and the research topics are set in the context of two themes— design strategies and design integrity. The process of adapting the results of research aimed at producing generic results in a form suitable for application to specific product types is illustrated by describing two projects in detail. Finally, the hetrogenous nature of the Newcastle EDC environment is described and particular references are made to industrial collaboration, technology transfer, training and education.     

Methods and tools for decision making in engineering design

This paper describes the background to the setting up of the Cambridge Engineering Design Centre. An overview of the design research and applications programme of the Cambridge EDC is given. Four research themes are identified: functional modelling, configuration and manufacturing optimization, materials and process selection, and process interpretation and management. Application areas include aerospace systems, heavy duty vehicles and medical equipment.     

Alloy optimisation of bainitic steel for large plastic mould

Based on the phase transformation theories, especially the T₀ concept of bainite transformation, alloy optimisation of bainitic steel with carbides has been carried out aiming at the produce of plastic mould with large cross-section. The effect of manganese and silicon on proeutectoid ferrite and bainite transformation is explored by dilatometric analysis, XRD and different microscopy techniques. The results show that after the alloy optimisation, the transformation of proeutectoid ferrite is suppressed and when the cooling rate is lower than 0·1°C?s^??1, the new lower bainite transformation appears by decreasing carbon capacity of austenite and promoting carbide precipitation. Industrial production proves that the optimised alloy SDP1 can meet the demand for the plastic mould with the thickness of 1050?mm.     

Application of a systematic design methodology: an engineering case study

The basic steps of a design process have been reviewed and applied to seek an optimum solution for an industrial design problem. The problem was about a mechanical swivel-joint in a sea-current-metering system for underwater marine use. It was expensive ($200) and not functioning properly because of rattling and high friction between parts. The objective was to design another joint of better performance and lower cost, if possible. Ten steps were defined and carefully followed to solve the problem. This led to the design and production of a good quality swivel-joint as far as performance, appearance and other aspects were concerned and the cost reduced by 40%. This design method, in addition to yielding good results, is suitable for the organization of the activities of new designers and design students.     

Optimization strategies in robust engineering design and computer-aided design

This paper reviews the fundamental ideas involved in robust engineering design (RED), and how they relate to computer-aided design. There are several areas of RED that may be successfully resolved by the use of statistical methods or ideas. This paper gives a general overview of several popular statistical strategies in RED and discusses how these strategies approach the statistical problems involved.     

A cross-disciplinary technology transfer for search-based evolutionary computing: from engineering design to software engineering design

Although object-oriented conceptual software design is difficult to learn and perform, computational tool support for the conceptual software designer is limited. In conceptual engineering design, however, computational tools exploiting interactive evolutionary computation (EC) have shown significant utility. This article investigates the cross-disciplinary technology transfer of search-based EC from engineering design to software engineering design in an attempt to provide support for the conceptual software designer. Firstly, genetic operators inspired by genetic algorithms (GAs) and evolutionary programming are evaluated for their effectiveness against a conceptual software design representation using structural cohesion as an objective fitness function. Building on this evaluation, a multi-objective GA inspired by a non-dominated Pareto sorting approach is investigated for an industrial-scale conceptual design problem. Results obtained reveal a mass of interesting and useful conceptual software design solution variants of equivalent optimality—a typical characteristic of successful multi-objective evolutionary search techniques employed in conceptual engineering design. The mass of software design solution variants produced suggests that transferring search-based technology across disciplines has significant potential to provide computationally intelligent tool support for the conceptual software designer.     

A chemical engineering design view of biotechnology

The possibilities of biotechnology are being widely discussed and promoted. Because of this there will be many studies directed at evaluating biotechnology projects. At some stage this will require the generation of potential process plant designs. The paper provides an introduction to those aspects of biotechnology which will be the concern of the chemical engineer, with an emphasis on design tasks. This is supported by a commentary on the similarities with and differences from mainline chemical engineering design. In addition the principal material relating to design has been drawn together from the available literature and summarized for engineers new to the area of biotechnology.     

Bond graph analysis in robust engineering design

Within engineering design, optimization often involves building models of working systems to improve design objectives such as performance, reliability and cost. Bond graph models express systems in terms of energy flow and can be used to identify key factors that influence system behaviour. Robust Engineering Design (RED) is a strategy for the optimization of systems through experimentation and empirical modelling; however, experiments can often be prohibitively expensive for large or complex systems. By using bond graphs as a front‐end to RED, experiments on systems could be designed more efficiently, reducing the number of experiments required for accurate empirical modelling. Two case study examples are given which show that bond graphs can be used to good effect in the empirical analysis of engineering systems. Copyright © 2000 John Wiley & Sons, Ltd.     

Si对中锰钢淬火配分组织和性能的影响

将20Mn5钢和20Mn5Si2钢进行淬火和配分(Q&P)工艺处理,用扫描电镜观测其微观组织,用X射线法测量残余奥氏体量,研究了Si对其微观组织和力学性能的影响.结果表明,试验钢中的奥氏体含量明显高于传统的TRIP钢和Q&P 工艺处理钢;在相同Q＆P工艺条件下,20Mn5Si2钢比20Mn5有较多的残余奥氏体,析出物数...     

热轧C-Si-Mn系TRIP钢的组织与力学性能

为了探讨热轧TRIP钢的制备工艺与其组织及力学性能的关系,采用热轧控冷工艺在实验室制备了C-Si-Mn系TRIP钢,利用光学显微镜、扫描电镜及透射电镜对试验钢的组织进行了观察,利用能谱仪对试验钢中的夹杂进行了观察.研究得到试验钢的力学性能为:σb=605 Pa,σs=440 Pa,δ=28.4%,σs/σb=0.73.定量金相检测结果表明,试验钢中三相含量分别为:残余奥氏体5.6%,铁素体67.6%,贝氏体26.8%.