成型尺寸对电子束选区熔化成型TC4合金性能与组织的影响

Research on effects of molding size on the properties and micro-structure of TC4 alloy formed by electron beam selective melting

采用电子束选区熔化制造技术制备不同成型尺寸的Ti-6Al-4V(TC4)钛合金试样,通过金相显微镜、扫描电镜、万能试验机和X射线衍射仪等研究设备,探究了不同成型尺寸对电子束选区熔化成型TC4钛合金试样的显微组织与力学性能的影响。结果表明:在R05、R06和R07这3种不同成型尺寸的试样中,成型尺寸越大,则拉伸强度和屈服强度越大,同时弹性模量和延伸率越小,即塑性越差;试样R05、R06和R07均发生韧窝断裂,但试样R05断口塑性较差,更接近脆性断裂;试样R07上下段分别形成双态组织和等轴组织,且距离打印基板位置越远,试样的层间结合率和粉末熔化率越低,即打印情况越差;对于成型尺寸最大的试样R05,由于其每层扫描时间长、热传递效果好,故其β柱状晶内形成了细针状马氏体和魏氏组织,而成型尺寸较小的R06试样则由于较高加工温度中的冷却,形成了网篮组织和片状α相组织。

Ti-6Al-4V(TC4)titanium alloy samples with different molding sizes were prepared by Electron Beam Selective Melting(EBSM)manufacturing technology.The influence of different molding sizes on the microstructure and mechanical properties of TC4 titanium alloy samples formed by EBSM was explored by means of metallographic microscopy,scanning electron microscopy,universal testing machine,X-ray diffractometer and other research equipments.The results show that in the three samples with different molding sizes of R05,R06 and R07,the larger the molding size,the greater the tensile strength and yield strength,and the smaller the elastic modulus and elongation,that is,the worse the plasticity;R05,R06 and R07 samples all have ligament fractures,but the fracture of R05 sample has less plastic,which is closer to brittle fracture;the upper and lower sections of R07 sample form bimorphic and isometric structures,and the farther away from the position of the printing substrate,the lower the bonding rate between the layers and the melting rate of the powder of the sample,that is,the worse the printing situation;the R05 sample with the largest molding size has fine needle martensitic and widmanstaten structure formed in itsβcolumnar lens due to the long scanning time of each layer and the good heat transfer effect,while the R06 sample with a smaller molding size forms basket structure and flakyαtissue due to the cooling in the high processing temperature.