Development of Novel Cyclic Rotating Bending Process for Control of Microstructure and Grain Refinement of Metal Tubes

作为一种新型的晶粒细化和组织控制方法，本文提出并研究了金属管的循环旋转弯曲加工方法。该原理是根据金属管的严重应变机理，采用连续方案与CRB方法，如Ono型旋转弯曲疲劳试验方法。为了验证该方法的有效性和正确性，研制了一种新的CR B加工装置，并利用该装置对镁合金管AZ31进行了实验。AZ31的CRB实验在恒定转速为20 rpm，温度为150 ~ 350℃的条件下进行。结果表明，与任意温度下热处理的CRB相比，较低加工温度下的CRB变形能有效细化晶粒尺寸。此外，镁合金管在室温下的拉伸性能，在200℃下进行CRB变形，导致最大的强度和延展性的提高。

As a novel grain refinement and microstructure control method, a cyclic rotating bending processing (CRB) method for metal tubes is proposed and investigated in the present study. The principle is on the basis of the severe straining mechanism of metal tube by using a continuous scheme with the CRB method such as Ono- type rotating bending fatigue testing method. To verify the validity and confirmation of the method, a new CR B processing apparatus is developed and then experiments with magnesium alloy tube AZ31 were carried out using the developed apparatus. CRB experiments for AZ31 are conducted under constant rotation speed of 20 rpm and under different temperatures from 150 to 350°C. As a result, it is seen that CRB deformation at the lower processing temperature is effective to refine the grain size compared with the case of heat treated ones at any temperature. In addition,tensile properties at room temperature of the magnesium alloy tube, which is subjected to CRB deformation at 200 °C, result in the most enhancements in the strength and ductility.