Effect Of Pretreatment Of Furnace And Heat Treatment Processes On Damping Performance Of ADI

Austempered ductile iron(ADI)is an excellent material with excellent comprehensive mechanical properties.At the same time,benefit by its special microstructure is composed of acicular ferrite,retained austenite and graphite spheres,it has good vibration and noise reduction,it can be used as transmission parts of facilities.In the past,people only focused on the study of mechanical properties of ADI,the study of damping performance of ADI is rarely reported,thus,this paper studies and analyzes the effect of pretreatment of furnace and heat treatment processes on the damping performance of ADI systematically,lay the foundation for the development of high damping ADI.In this paper,dynamic mechanical analyzer(DMA)was used to test the damping performance of ADI samples which are under different pretreatment of furnace and heat treatment processes,and microstructures were analyzed by metallographic microscope and X ray diffractometer(XRD).The strain-internal friction curves of different pretreatment of furnace processes showed that: when the strain is 0.05 %,when the amount of primary inoculant is 1.0~1.4 %,the damping performance is better than others,the internal friction value Q-1 is more than 0.02;when the amount of post inoculant is 0.2 %,the damping performance is best,the internal friction values Q-1 reached about 0.025;when the amount of spheroidizing agent is 1.1~1.5 %,the damping performance is better than others,the internal friction value Q-1 is more than 0.018;Combined with microstructures analysis: when the differences of shape,size and spheroidization rate of graphite nodule in ADI are not huge,the higher of the number of graphite spheres,the more beneficial to improve the damping performance of ADI.The strain-internal friction curves of different heat treatment processes showed that: when the strainis 0.05 %,when the austenitizing temperature is 900 ?,the damping performance is the best,the internal friction value Q-1 reached about 0.017;when the first step isothermal quenching temperature is 240~260 ?,the damping performance is better than others,the internal friction value Q-1 is more than0.014;when the second step isothermal quenching temperature is 320 ?,the damping performance is best,the internal friction value Q-1 is more than 0.017;when the first step isothermal quenching time is 10~15 min,the damping performance is better than others,the internal friction value Q-1 is more than0.016;when the second step isothermal quenching time is 40~60 min,the damping performance is better than others,the internal friction value Q-1 is more than 0.017,completely accord with the standard of high damping alloy(Q-1>0.01);Combined with microstructures analysis: the more nucleation number in matrix of ADI,the smaller of the grain size,the more beneficial to improve the damping performance of ADI,at the same time,the residual austenite content in the matrix has some influence on the damping performance of ADI.The paper found that the damping performance of ADI is sensitive to the test temperature and frequency,test results showed that: with the increase of the test temperature,the damping performance of ADI gradually increased,the internal friction peak value is reached in the range of 180~220 ?,Q-1 is about0.029,with the increase of temperature,the damping performance decreases gradually;when the test frequency range is 1~100 Hz,with the increase of the test frequency,the damping performance of ADI has a rising trend.