加载速度对TiAl基合金缺口弯曲断裂机制的影响  

Effect of Loading Speed on the Notch Bending Fracture Mechanism of TiAl-Based Alloys

作　　者：曹睿[1] 雷明霞[1] 陈剑虹[1] 张继[2] 

机构地区：[1]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 [2]钢铁研究总院,北京100081

出　　处：《稀有金属材料与工程》2008年第7期1257-1260,共4页Rare Metal Materials and Engineering

基　　金：国家自然科学基金(50471109);甘肃省自然科学基金(3ZS061-A25-037)

摘　　要：主要就加载速度对TiAl基合金2种组织缺口弯曲断裂机制的影响进行了详细研究。研究结果表明:在缺口弯曲试验中,裂纹沿着局限于缺口根部中心线上的高应力区起裂并扩展;全层组织断裂韧性随加载速度的变快而增加,而双态组织断裂韧性随加载速率的增大几乎没有变化,这主要是由于在不同加载速度下全层组织在加载速度快和慢时的断裂过程不同,双态组织则是相同的;全层组织试样具有较差的拉伸性能,但是具有较高的断裂韧性,这是由于2种试验时的断裂机制不同。在拉伸试验时大层团晶粒引起严重的损伤和低的强度;然而在3PB试验中大层团形成更大的分叉裂纹以及形成穿过主裂纹扩展的更大阻碍物。Based on the results of notch 3 point bending （3PB） tests with various loading speeds and the observation of fracture surfaces, the effects of loading speed on the damage and fracture mechanisms of fully lamellar （FL） and duplex phase （DP） TiAl alloys are studied. It is shown that the main crack propagates by the stretching of a bifurcated crack through the strip with high normal stress, which is narrowly constrained near the centerline. With loading speed deceasing, the notch fracture toughness of FL specimens decreases, and the notch fracture toughness of DP alloy is nearly the same, because the fracture process in FL specimens is different at the different loading speeds, however, the fracture process in DP specimens is the same. The coarse FL TiAl alloy specimen has a poorer tensile strength but a higher fracture toughness due to the different fracture mechanisms for the tensile test and 3PB notched test. The large lamellar grains cause a heavy damage and a low strength for the tensile tested specimen, however a large bifurcated crack and a bigger obstacle to be bypassed by the main crack for the fracture toughness test.

关 键 词：TIAL基合金 加载速率 缺口韧性 断裂机制 

分 类 号：TG115.5[金属学及工艺—物理冶金]