Metallurgical Aspects of Deformation Processing

该研究完全集中在高温变形上，有五个子部分：*1。 奥氏体相场中高温奥氏体的动态转变。 这一新发现的机制的以下方面将进行研究：i）变量选择的应力的影响; ii）临界应变和铁素体体积分数的组成的影响; iii）在转变过程中的间隙和替代分配的特点; iv）魏氏铁素体的合并和再转变为奥氏体;和v）动态转变的热力学。 *2。 Ti和Zr合金的动态相变。 最近在麦吉尔的研究表明，Ti和Zr合金易受动态相变的影响。 而在铁素体合金中，变形会提高Ae 3，而在六方晶系材料中，变形会降低β转变。 这种转换遵循Burgers关系，因此与适用于钢的位移机制不同。 在这些材料中的动态转变机制是未知的，将被确定。 这些包括热力学背景以及微观结构、结构和成分效应。* 3. Mg和Ti合金中的孪晶、变体选择和动态应变时效。 在初级、二级和三级双胞胎期间，将继续研究菌株调节对变体选择过程的作用。 特别感兴趣的是在剪切带附近发生的调节和负速率敏感性对这个过程的影响。 另一方面涉及与稀土和常规溶质两者相关的动态应变老化。 这具有使得能够使用较便宜的合金元素如Ca来生产期望的“稀土”织构的目的。 将确定和探讨实现这一目标的机制。4. 扭转试验力学及其在热轧模拟中的应用。 亨基应变继续被用于分析剪切实验，如扭转，仍然是一个有争议的话题。 申请方将通过澄清使用Hencky菌株的合理性来促进这一辩论。 将对带材（短道次间时间）和板材（长道次间时间）轧机计划进行模拟。 阐明了动态变换在工业轧制中的作用，并提出了修正跳动台模型以考虑动态变换影响的必要性。*5。 连续和不连续动态再结晶。 钢加工的精确控制依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，更详细地审查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 Widmanstätten 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).**