Metallurgical aspects of deformation processing

这项研究涵盖了以下五个不同的主题。 非平衡相图。在制定轧钢规程时，一般采用Fe-C相图。它是基于未变形奥氏体相(高温相)的存在。然而，当奥氏体在轧钢厂发生变形时，这种“平衡”图就不再适用了。我们正在进行高达100度的测试。温度高于预测的转变温度并形成铁素体(低温相)，表明常规相图不适用。在对各种钢的实验中，我们正在确定实际相图如何依赖于应变、成分等。 动态再结晶条件下的高温流动曲线。轧钢厂的精确建模和控制要求能够准确地预测钢材的流动应力(变形抗力)。当钢在变形过程中开始再结晶时，这一过程被称为动态再结晶，这一目标变得更加难以实现。我们已经开发了使用Avrami动力学对这类曲线进行精确建模的方法，并正在继续改进这一方法。 镁合金的物理冶金。机械孪晶在镁合金中很常见。尽管这种双胞胎有六个对称的变种，但只有少数几个形成。我们正在确定支配它们形成的“变种选择”的“法则”。另一个重要的关注点是稀土添加对这类合金行为的影响。这些都是通过机械试验进行研究的。 钛合金的线性摩擦焊接钛压缩机叶片可以通过固态工艺(不熔化)连接到压缩机盘上。制造坚固焊缝所需的条件正在通过适当的试验来确定。 轧制过程的扭转模拟。我们正在继续进行扭转模拟，以确定各种钢的热轧三个临界温度，以期改进轧制规程。

The research proposed covers the following five distinct topics. Non-Equilibrium Phase Diagrams. The Fe-C phase diagram is generally employed in the planning of steel rolling schedules. It is based on the presence of undeformed austenite (the high temperature phase). However, when austenite is being deformed in rolling mills, this "equilibrium" diagram no longer applies. We are carrying out tests as much as 100 deg. C above the predicted transformation temperature and forming ferrite (the low temperature phase), indicating the inapplicability of the conventional diagram. In experiments on various steels, we are determining how the actual phase daigram depends on strain, composition, etc. The High Temperature Flow Curve under Conditions of Dynamic Recrystallization. The accurate modeling and control of rolling mills requires the ability to predict the flow stress (deformation resistance) of steel with accuracy. When steel begins to recrystallize during deformation, a process known as dynamic recrystallization, this goal becomes more difficult to achieve. We have developed methods for the accurate modeling of such curves using what are known as Avrami kinetics and are continuing to improve this approach. Physical Metallurgy of Mg Alloys. Mechanical twinning is very common in Mg alloys. Although there are six symmetrical varieties of such twins, only a few of them form. We are determining the 'laws' of "variant selection" that govern their formation. Another important focus is on the effect of rare earth additions on the behaviors of such alloys. These are being investigated using mechanical tests. Linear Friction Welding of Titanium Alloys. Titanium compressor blades can be joined to compressor discs by solid state processes (without melting). The conditions that are required to make strong welds are being determined by means of appropriate tests. Torsion Simulation of Rolling. We are continuing to do torsion simulations to determine the three critical temperatures of hot rolling in a variety of steels with a view to improving rolling schedules.