【作者】 王斌；

【导师】 王进； 马大衍；

【作者基本信息】 青岛理工大学 ， 机械工程（专业学位）， 2018， 硕士

【摘要】 金属材料的许多性能,如机械性能,物理、化学性能等都受到材料晶粒尺寸的影响。细化晶粒,可以从很大程度上提高材料的性能,但由于技术水平及加工工艺的限制,在很长时间内人们只能将晶粒细化至微米级,强化效果不尽如人意。等通道转角挤压(Equal Channel Angular Pressing,简称ECAP)技术是一种通过近似纯剪切的剧烈塑性变形使金属材料的晶粒尺寸细化至纳米级的一种制备超细晶材料的一种重要手段。目前,人们已经应用ECAP技术对多种纯金属和合金进行了试验,有着重要的研究价值。本文探索的是对T2的ECAP变形,但由于在进行ECAP挤压变形时,需要较大的变形力,且铜的变形抗力也相对较大,因此对设备的要求往往较高。为降低对试验设备需求,确保试验能够连续进行,本文首先通过计算设计了一套新的挤压模具,为分析这套模具的优劣,利用Deform-3D软件进行了不同角度、不同形状的模具在挤压过程中的应力、应变状态及其挤压力进行了比较,其模拟结果表明,圆形截面试样,在其模具内角为120°时,其所需的变形力最小,其应变的均匀程度也相对较好。为了验证数值模拟结果得有效性,本文选择圆形截面,模具内角为120°的设计加工生产了模具实物,并对圆形试样进行了ECAP挤压试验,并对挤压完成后的试样进行了性能试验,试验结果表明,所生产模具能够在630kN压力机上完成直径为12mm圆形截面试样得ECAP挤压,经ECAP挤压后的试样的硬度、强度都有了明显的提高,且其提高的程度与模拟结果的应变量呈正相关关系。更多还原

【Abstract】 Many properties of metallic materials,such as mechanical,physical and chemical properties,are affected by grain size.Grain refinement can greatly improve the properties of the material,but due to the technical level and processing technology constraints,people can only refine the grain to micron size for a long time,and the strengthening effect is not satisfactory.Equal Channel Angular Pressing(ECAP)technology is an important method for preparing ultrafine grained materials by means of severe plastic deformation of approximate pure shear to refine the grain size of metal materials to nanometer scale.At present,many pure metals and alloys have been tested by ECAP technology,which has important research value.In this paper,the ECAP deformation of T2 is explored,but due to the large deformation force is needed in ECAP extrusion,and the deformation resistance of copper is relatively large,the requirement of equipment is always high.In order to reduce the demand for test equipment and ensure that the test can be carried out continuously,a new extrusion die is designed by calculation.In order to analyze the advantages and disadvantages of this set of dies,different angles are carried out by using Deform-3D software.The stress,strain and extrusion force of die with different shapes during extrusion are compared.The simulation results show that the deformation force of circular section specimen is the smallest when the internal angle of the die is 120°.The strain uniformity is also relatively good.In order to verify the validity of the numerical simulation results,the design and manufacture of the round cross section with 120° inner angle of the die was carried out in this paper.The ECAP extrusion test was carried out on the circular specimen,and the properties of the finished specimen were tested.The test results show that the die can be extruded by ECAP on the 630 kN press with a diameter of 12 mm circular section,and the hardness and strength of the samples after ECAP extrusion have been obviously improved.The degree of improvement is positively correlated with the strain of simulation results.更多还原