γ-TiAl基合金压缩损伤与断裂行为的研究  

Compression Damage and Fracture Behaviors of γ-TiAl Based Alloys

作　　者：林有智 傅高升[1,2] 曹睿[3] 陈剑虹[3] 胡大为 

机构地区：[1]宁德职业技术学院机电工程系,福建宁德355000 [2]福州大学机械工程及自动化学院,福建福州350002 [3]兰州理工大学甘肃省有色金属新材料省部共建国家重点实验室,甘肃兰州730050 [4]Interdis-ciplinary Research Central, University of Birmingham, Birmingham, UK

出　　处：《稀有金属》2014年第2期334-340,共7页Chinese Journal of Rare Metals

基　　金：国家自然科学基金项目(50471109)资助

摘　　要：通过对γ-TiAl基合金压缩断裂及压缩卸载试验和试样断口与表面的扫描电镜(SEM)观察,分析压缩应力对裂纹产生、扩展及裂纹形态的影响,进而对该材料的压缩损伤与断裂行为进行较为深入的研究。压缩试验是室温下在Instron 1341试验机上进行的。结果表明,损伤起始于材料的塑性区载荷下降阶段,材料在断裂前发生很大的塑性变形,其压缩时有较大的塑性缓冲;随着压缩卸载应力的增大,观察到的试样表面裂纹依次增多或扩展增长,材料损伤的程度与压缩应力成正比。在压缩试样断口的中部发现存在的一个纵向韧带,当外加载荷增加,两个由压缩接触端面起裂的倾斜剪切裂纹扩展到试样中部,然后通过剪切穿过纵向韧带而连接,并诱发试样的完全脆性断裂。两个端面的切应力是裂纹形成的主要控制因素。该材料的压缩性能比拉伸性能更佳的主要原因是由于压缩时材料的损伤起始于塑性阶段,产生沿45°方向剪应力最大方向的剪切断裂和沿着压缩轴方向的准解理断裂的混合形式,而普通拉伸时材料损伤起始于弹性阶段,发生完全脆性解理断裂,在低应力下试样就会断裂。Based on the results of loaded crack and loaded-unloaded compression testing, and scanning electron microscopy （SEM） observations of corresponding cracks and fracture surfaces for γ-TiAl based-alloys, analyzing the effect of compression stress on crack initiation, propagation and crack morphology, the material compression damage and fracture behaviors were studied. The compression tests were performed on the Instron 1341 testing machine at room temperature. The results showed that the damage initiated in plastic zone load-descending stage on compression of material, and the material still had great plastic deformation and plastic buffer before fracture; with the increase of the compression stress, the cracks were observed to increase successively and cause connection. The damage of material was in direct ratio with compression stress. A longitudinal ligament was found usually in central of compression frac- ture surfaces. With the load increasing, two slant shear cracks initiated on compression contact surface and extended to the central ofsample, and then were connected by shear through the longitudinal ligament, and induced completely brittle fracture of the sample. The shear stress on eompression contact surfaces was the main factors for controlling the initiation of cracks. The eompression perform- ante of the material was much better than the tensile properties. The main reason was the damage initiation in plastic stage on compres- sion of material, and the deformation mechanisms in compressive tests were controlled by shear stress along the 45°direction and axis stress, and fracture mechanisms of compressive tests were quasi-cleavage fracture. And the damage initiation in the elastic stage on ten- sile of material, fracture mechanisms of tensile tests were completely brittle cleavage fracture under low stress.

关 键 词：TIAL基合金 压缩 损伤行为 断裂行为 裂纹 

分 类 号：TG146[一般工业技术—材料科学与工程]