热处理对Fe-36Ni因瓦合金箔热膨胀及力学性能的影响

Effect of heat treatment on thermal expansion behavior and mechanical properties of Fe-36Ni Invar alloy foil

研究了60μm厚Fe-36Ni因瓦合金箔冷轧态、退火态及淬火态的热膨胀行为及力学性能演变规律和作用机理。结果表明,冷轧态合金具有最小的热膨胀系数,淬火态次之,退火态热膨胀系数最大;热处理可有效提高合金的居里温度Tc,从而增大使用温度范围,900℃保温1.5 h淬火试样具有最优的热膨胀性能(α¯_((20-100℃))=1.02×10^(-6) K^(-1),T_(c)=276℃),自由取向晶粒的增加是导致合金热膨胀系数增大的原因。与冷轧态相比,热处理后合金发生完全再结晶,并产生退火孪晶伴随有晶粒尺寸的变化和∑3n晶界比例快速升高,其中800℃保温1.5 h淬火试样的晶粒最细小(6.6μm),∑3^(n)晶界占比最高,具有最高的屈服强度(267 MPa)和抗拉强度(414 MPa)。淬火处理试样的综合性能优于退火试样。相同热处理方式下,升高热处理温度,一方面降低热膨胀系数,提高居里温度;另一方面也降低了强度。

Evolution of thermal expansion behavior and mechanical properties of Fe-36Ni Invar alloy foil with thickness of 60μm under cold rolled,annealed and quenched conditions was investigated,respectively.The results show that the cold rolled alloy has the smallest thermal expansion coefficient,the quenched state is second,and the annealed state has the largest thermal expansion coefficient.Heat treatment can effectively increase the Curie temperature Tc of the alloy to increase the service temperature range,and the specimen quenched at 900℃for 1.5 h has the best thermal expansion properties(α¯_((20-100℃))=1.02×10^(-6) K^(-1),T_(c)=276℃).The rise in the number of free oriented grains is the main reason for the increase of thermal expansion coefficient.Compared with cold rolled state,complete recrystallization and annealing twinning of the alloy occur after heat treatment,accompanied by change in grain size and a rapid increase in the proportion of∑3^(n) grain boundaries.The specimen quenched at 800℃for 1.5 h has the smallest grain size(6.6μm)and the highest proportion of∑3^(n) grain boundaries,giving the highest yield strength(267 MPa)and tensile strength(414 MPa).In summary,the comprehensve properties of the quenched specimen are better than that of the annealed specimen.However,under the same heat treatment method,increasing the heat treatment temperature on the one hand reduces the coefficient of thermal expansion and increases the Curie temperature,and on the other hand reduces the strength.