Modified tin-phosphor bronze alloy and a preparation method thereof

A preparation method of a modified tin-phosphor bronze alloy, wherein, the preparation method comprises:

• subjecting a pretreated tin-phosphor bronze alloy workpiece to modification treatment so as to obtain the modified tin-phosphor bronze alloy;
• wherein, the modification treatment comprises a cold rolling deformation step and a heat treatment step carried out sequentially;
• wherein, the average grain size of the pretreated tin-phosphor bronze alloy workpiece is 1-3 μm;
• the deformation amount of the cold rolling deformation step is 7-15%;
• the temperature of the heat treatment step is 380-500° C.;
• the heat preservation time of the heat treatment step is 1-4 hours;
• the preparation method further comprises a preparation process flow of the pretreated tin-phosphor bronze alloy workpiece, which comprises a batching step, a horizontal continuous casting step, a homogenization annealing step, a face milling step, a cold rolling cogging step, a first recrystallization annealing step, an intermediate rolling deformation step, a second recrystallization annealing step, a finish rolling deformation step, a third recrystallization annealing step, a bottom reservation rolling step, and a fourth recrystallization annealing step carried out sequentially, wherein the temperature of the homogenization annealing step is 650-690° C.;
• the temperature of the third recrystallization annealing step is 650-750° C., and the heat preservation time of the third recrystallization annealing step is preferably 20-60 seconds;
• the temperature of the fourth recrystallization annealing step is 600-650° C., and the heat preservation time of the fourth recrystallization annealing step is preferably 20-60 seconds;
• the atmospheres for the third recrystallization annealing step and the fourth recrystallization annealing step are each independently a second mixed gas of nitrogen and hydrogen, and the second mixed gas comprises 3-5% of H2 and 95-97% of N2 in percentage by volume;
• the modified tin-phosphor bronze alloy comprising the following elements in percentage by mass:
• 4.0-10 wt % of Sn, 0.01-0.3 wt % of P and the balance of Cu and inevitable impurity elements, wherein, the average grain size of the modified tin-phosphor bronze alloy is 1-3 μm, the grain size is in normal distribution, and the standard deviation of the grain size is below 0.8 μm;
• the proportion of the total low-ΣCSL grain boundary in the modified tin-phosphor bronze alloy in the whole grain boundary is 66-74%, and in the total low-ΣCSL grain boundary, the ratio range of (Σ9+Σ27)/Σ3 is 0.12-0.23:1.