Enhanced Mechanical Properties of QAl9-4 Aluminum Bronze for High-Speed-Rail Brake Systems with a Pulsed Magnetic Field.

To improve the mechanical properties and wear resistance of QAl9-4 aluminum bronze alloy parts of high-speed rail brake calipers, the solid aluminum bronze alloy was treated with a pulsed magnetic field in which the magnetic induction intensity was 3T at room temperature. After that, a tensile test and a friction and wear test were carried out on the alloy. The results indicate that the magnetic field promotes the movement of low-angle grain boundaries less than 2° and splices to form subcrystals or fine crystals, which reduces the mean grain size of the alloy. The disordered dislocation changed into a locally ordered dislocation line, the dislocation distribution became uniform, and the dislocation density increased, which simultaneously improved the alloy's tensile strength and elongation. The elongation increased by 10.2% compared with that without the magnetic field. The increase in strength can provide strong support for the wear-resistant hard phase, and the enhancement of plasticity can increase the alloy's ability to absorb frictional vibration. Therefore, it was hard for cracks to form and extend, and the specimen's average friction coefficient was reduced by 22.05%. The grinding crack width and depth decreased, the wear debris became more uniform and fine, and the alloy's wear resistance increased.