Optimization of Heat Treatment Process for QBe2 Beryllium Bronze Based on Orthogonal Experimental Design

The heat treatment process parameters of QBe2 beryllium bronze alloy were systematically optimized using L₉(3³) orthogonal experimental design. Under the condition of solution treatment time of 10 min, the effects of solution temperature (780, 800, 820℃), aging temperature (300, 325, 350℃), and aging time (1, 2, 3 h) on the hardness and microstructure of the alloy were investigated. The results show that aging temperature has the most significant effect on alloy hardness (range R=28.7), followed by solution temperature (R=27.0), and aging time has a relatively small effect (R=14.3). Analysis of variance reveals that aging temperature and solution temperature have a highly significant effect on hardness (P < 0.01), while aging time has a significant effect (P < 0.05). The optimal process parameters are solution treatment at 800℃ for 10 min + aging at 325℃ for 3 h, and the Vickers hardness of the alloy reaches 385±6 HV_0.1. Microstructural analysis reveals that the alloy consists of an α-Cu matrix, a small amount of residual β phase, intragranular γ′ precipitates, and grain boundary discontinuous precipitates. At 325℃ aging, the size of the γ 'phase is nanoscale and evenly distributed, achieving the best precipitation strengthening effect. At 350℃, over-aging occurs, characterized by precipitate coarsening and discontinuous precipitation, leading to a reduction in hardness. The strengthening mechanisms mainly include the Orowan looping mechanism, coherency strain strengthening, and solute strengthening, with multiple mechanisms working synergistically to achieve high strength.