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使用微机自动控制相变内耗仪,以0.7Hz频率测量Cu-25.83wt-％Zn-3.96wt-％Al合金在贝氏体相变温区等温过程中的内耗和频率随时间的变化,实验结果显示,在孕育期内随时间出现内耗峰值Q_(max)~(-1)且Q_(max)~(-1)随等温温度升高(孕育期缩短)而升高,达到Q_(max)~(-1)所需时间却随等温温度升高而缩短.在等温初期频率最低,随时间延长逐渐上升至稳定值.在施加8×10~5Pa拉应力的条件下,重复上述等温测量表明,Q_(max)~(-1)升高,达到Q_(max)~(-1)所需的时间缩短,且初期频率下降更为显著. 本文揭示:Cu-Zn-Al合金贝氏体相变存在类似于热弹性马氏体相变的点阵软化现象。在贝氏体相变孕育期内存在预相变的主要过程为形核。等温内耗的变化规律可根据相变理论和局部软化理论,通过孕育期内形核率J~*的变化作出解释。
The internal friction and frequency of Cu-25.83wt-% Zn-3.96wt-% Al alloy in the isothermal process of bainite transformation temperature were measured at 0.7Hz by using microcomputer automatic control system. The experimental results Showed that the peak of internal friction peak Q_ (max) ~ (-1) and Q_ (max) ~ (-1) increased with increasing isothermal temperature (shortening of incubation period) and reaching Q max ~ (-1) is shortened with the increase of isothermal temperature.The frequency is the lowest at the beginning of isothermal and gradually increases to a stable value with the extension of time.Under the application of tensile stress of 8 × 10-5Pa, the isotherm measurement is repeated, The time required to reach Q max (-1) is shortened and the initial frequency decrease is more significant when the Q max (-1) increases.It is revealed that the bainite transformation of Cu-Zn-Al alloy There is a lattice softening phenomenon similar to the thermoelastic martensitic transformation. The main process of pre-phase transformation during the bainite transformation incubation period is nucleation. The variation law of isothermal internal friction can be explained by the phase change theory and the local softening theory through the change of the nucleation rate J ~ * during the inoculation period.