低温条件下QTD900-8的力学性能研究

Investigation on Mechanical Properties of QTD900-8 under Low Temperature Condition

以QTD900-8材料为研究对象,采用拉伸、冲击、布氏硬度测试以及扫描电镜的分析方法,研究其在低温条件下的力学性能和断口形貌特征,结果表明:(1)随着温度的降低,QTD900-8的力学性能变化很大,在-60℃时,相对于常温条件抗拉强度提高了19.8%,伸长率降低了33.0%,冲击韧度下降超过了70%,硬度提高了18.4%;(2)随着温度的降低,QTD900-8发生了韧性断裂、混合型断裂、脆性断裂变化的过程;(3)低温下,拉伸断裂过程中首先在石墨处产生裂纹,进而扩散至整个截面,导致材料断裂。

By using QTD900-8 material as investigation object,adopting tensile test,impact test,HB test and SEM analysis,the mechanical properties,fracture morphology characteristics of the material were investigated,the result showed:(1)With the decrease of temperature,the mechanical properties of QTD900-8 vary greatly:compared with normal temperature condition,at -60 ℃,the tensile strength was increased by 19.8%,the elongation decreased by 33.0%,the impact toughness decreased by more than 70%,the hardness elevated by 18.4%.(2)As the temperature drops,the process of ductile fracture,mixed mode fracture and brittle fracture occurred with QTD900-8.(3)At low temperature,cracks first occur in graphite in the process of tensile fracture,and then spread to the whole section,which led to the fracture of the material.