Metallurgical Aspects of Deformation Processing

建议的研究完全集中在高温变形上，分为五个子部分： 1.奥氏体相场中高温下的奥氏体动态转变这一新发现的机制将从以下几个方面进行研究：1)应力对变种选择的影响；2)成分对临界应变和铁素体体积分数的影响；3)相变过程中的间隙和置换分配特征；4)魏氏铁素体的聚集和再转变为奥氏体；5)动态相变的热力学。 2.钛、锆合金的动态相变。最近在McGill的研究表明，钛和锆合金对动态转变很敏感。而在铁素体合金中，形变提高了Ae3，在六方相材料中，形变降低了β相变。这种转变遵循Burgers关系，因此不同于适用于钢的置换机制。这些材料中的动态转变机制尚不清楚，将被确定。这些因素包括热力学背景以及微观结构、织构和成分效应。 3.镁钛合金中的孪晶、变种选择和动态应变时效在第一次、第二次和第三次双胞胎过程中，将继续研究菌株适应在变异选择过程中的作用。特别令人感兴趣的是在剪切带附近发生的调节以及负速率敏感性对这一过程的影响。另一个方面涉及与稀土和常规溶质有关的动态应变时效。这样做的目的是使用价格较低的合金元素，如钙，生产出理想的“稀土”质地。将确定和探索实现这一目标的机制。 4.扭转测试力学及其在热轧模拟中的应用。亨基应变继续用于剪切实验的分析，如扭转，仍然是一个有争议的话题。申请人将通过澄清使用Hencky菌株的正当理由来促进这场辩论。将对带钢(短中间时间)和中厚板(长中间时间)两种轧制计划进行模拟。将阐明动态转变在工业轧制中的作用，以及修改轧制表模型的必要性，以考虑动态转变的影响。 5.连续和不连续动态再结晶。对钢材加工的精确控制有赖于对静态和动态再结晶的详细了解。将继续在这一重要领域开展研究，更详细地研究连续动态再结晶在多向锻造和其他严重塑性变形(SPD)途径中的作用。

The research proposed is focused entirely on high temperature deformation, with five sub-components: 1. Dynamic Transformation of Austenite at Temperatures High in the Austenite Phase Field. The following aspects of this newly discovered mechanism will be investigated: i) effect of stress on variant selection; ii) effect of composition on critical strain and ferrite volume fraction; iii) characteristics of interstitial and substitutional partitioning during transformation; iv) coalescence of Widmanstä tten ferrite and retransformation to austenite; and v) thermodynamics of dynamic transformation. 2. Dynamic Transformation of Ti and Zr Alloys. Ti and Zr alloys have recently been shown at McGill to be susceptible to dynamic transformation. While in ferritic alloys, deformation raises the Ae3, in the hexagonal materials, deformation lowers the beta transus. This transformation follows the Burgers relation and is thus unlike the displacive mechanism that applies to steel. The mechanisms of dynamic transformation in these materials are unknown and will be determined. These include the thermodynamic background as well as the microstructural, textural and compositional effects. 3. Twinning, Variant Selection and Dynamic Strain Aging in Mg and Ti Alloys. The role of strain accommodation on the variant selection process will continue to be investigated during primary, secondary and tertiary twinning. Of particular interest is the accommodation taking place in the vicinity of shear bands and the effects of negative rate sensitivity on this process. Another aspect concerns the dynamic strain aging associated with both rare earth and conventional solutes. This has the aim of enabling the production of desirable "rare-earth" textures using less expensive alloying elements such as Ca. The mechanisms that permit this to be achieved will be identified and explored. 4. Mechanics of Torsion Testing and Application to Simulation of Hot Rolling. The Hencky strain continues to be employed in the analysis of shear experiments such as torsion and remains a controversial topic. The applicant will contribute to this debate by clarifying the cases where use of the Hencky strain is justified. Simulations will be carried out of both strip (short interpass time) and plate (long interpass time) mill schedules. The role of dynamic transformation in industrial rolling will be clarified together with the need to modify runout table models so as to take the effect of dynamic transformation into account. 5. Continuous and Discontinuous Dynamic Recrystallization. The accurate control of steel processing relies on a detailed understanding of static and dynamic recrystallization. Research will continue to be carried out in this important area, with more detailed examinations of the role of continuous dynamic recrystallization in multi-directional forging and other avenues of severe plastic deformation (SPD).