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

作为一种新型的细晶组织控制方法，本文提出并研究了金属管材的循环旋转弯曲加工方法。其原理是基于金属管材的强烈应变机理，采用连续的CRB方法，如Ono型旋转弯曲疲劳试验法。为了验证该方法的有效性和有效性，研制了一种新型的CR-B加工装置，并利用该装置对AZ31镁合金管材进行了试验。在恒定转速20rpm和150~350℃不同温度下对AZ31进行了CRB试验。结果表明，与任何温度下的热处理相比，在较低的加工温度下进行CRB变形可以有效地细化晶粒度。此外，在200°C进行CRB变形的镁合金管材在室温下的拉伸性能导致强度和塑性得到最大程度的提高。

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.