时效温度对Monel K500合金微观结构与性能的影响

Effect of aging temperature on microstructure and properties of Monel K500 alloy

采用固溶+时效工艺对Monel K500合金进行了时效处理,通过显微硬度和拉伸性能测试,以及OM、SEM、TEM、XRD等分析表征,研究了时效温度对Monel K500合金组织结构以及性能的影响。结果表明,时效处理后形成的多边形TiC颗粒强化相主要分布在晶界处,同时晶界处Al元素含量增多,过饱和固溶体发生脱溶分解,Al、Ti元素以Ni_(3)(Al,Ti)第二相形式析出,合金硬度与强度提高。经电化学腐蚀后,该合金生成腐蚀产物NiO和CuO。随着时效温度的升高,第二相含量逐渐增加,但过高的温度导致第二相长大,故时效温度为560~700℃时,强化效果随着温度升高呈先升高后降低趋势。时效温度为630℃时,合金的硬度(HV)为329.26,强度994.56 MPa,均达到最大值,但耐腐蚀性能在该温度下反而有所降低。

The heat treatment of solution + aging process was conducted on Monel K500 alloy. For investigating the effect of aging temperature on the microstructure and properties of Monel K500 alloy,the micro-hardness and tensile properties were measured and the microstructure of the samples was analyzed by OM, SEM, TEM and XRD. The results showed that hardening phase of polygonal TiC particles mainly distributed at grain boundaries. Meanwhile, Al content at the grain boundary increases after aging treatment, and precipitation decomposition in the supersaturated solid solution occurred,which caused Al and Ti elements to precipitate in the form of Ni_(3)(Al, Ti) second phase. The corrosion products NiO and CuO formed after electrochemical etching. With the increasing aging temperature, the volume fraction of precipitates increases, but the high temperature causes the coarsening of precipitates.So, the strengthening effect firstly increases and then decreases with the increase of aging temperature in the range of 560~700 ℃. After aging treatment at 630 ℃, the hardness(HV) and strength of the Monel K500 alloy can reach the maximum value of 329.26 and 994.56 MPa, respectively. However, the corrosion resistance decreases when alloy subject to aging treatment at this temperature.