模具铜合金材料热处理工艺的研究

【作者】 刘明朗；

【导师】 路阳； 苏义祥；

【作者基本信息】 兰州理工大学 ， 材料科学与工程， 2004， 硕士

【摘要】 铝青铜因具有优良的力学性能和耐磨性、耐蚀性和抗氧化性在机械工业、飞机和汽车制造工业、船舶和海洋工业中都得到了广泛的应用。随着现代工业的飞速发展，机械产品对铝青铜的性能要求也越来越高，传统的牌号的铝青铜如QAl10-3-1.5和QAll10-4-4等已经难以满足某些特殊工况条件下的使用要求。 因此，许多科研人员正致力于新型铝青铜的开发，本课题组也研究开发一种应用于制造模具的、高强度的、高硬度的新型铝青铜合金。本文研究了该模具铜合金在铸态下的组织结构与力学性能的关系、均匀化退状态下的组织演变过程及优化其热处理工艺。结果表明： 1．该铝青铜铸态下的组织为（α+β′+γ₂+K）。铸态下存在不平衡相、存在着过饱和的难溶元素和枝晶偏析，除了以上三种情况外，晶界和枝晶界上还有难溶元素的金属间化合物、杂质相、非金属夹杂等。该铝青铜铸态下硬度、强度较高，韧性较低。晶粒大小、α相含量、γ₂相分布及K相的形状等影响着铝青铜铸态下的力学性能。铸态下铝青铜的晶粒为0.000475cm，晶粒粗大会使该铝青铜的塑性和韧性同时降低；α相含量少，γ₂粗大并沿晶界分部是导致该铜合金脆性的主要原因：合金中的K相，主要起弥散强化的作用，合金中花状K相较大，在一定程度上恶化了合金的性能。 2．低温均匀化退火态的组织仍为β′、α、γ₂、K，该铝青铜低温退火下仍表现为强度、硬度高，冲击韧性有明显下降的趋势。 3．在加热温度变化，保温时间不变的一组均匀化退火实验中，980℃均匀化退火转变的最完全，但由硬度实验和冲击韧性实验可以看出在950℃时性能最好。 4．在加热温度不变，保温时间变化的一组均匀化退火实验中发现保温时间对k相影响较大，当950℃、20h保温时k相完成了析出、长大、分裂、再聚集的过程，完全均匀化；当950℃、2h保温时基体相为（α+γ₂）、α、γ₂，均匀化完全，保温时间继续增加时初晶的γ₂相粗化。从测得的硬度可以看出，在950℃、2h保温时硬度最高。 5．最佳的热处理工艺是：（950℃、2h、油淬）+（500℃、5h、空冷），在此工艺下硬度为41.17HRC，冲击韧性为0.713kgf．m，抗拉强度为625Mpa。达到硬度最大值45.84 HRC的工艺是（950℃、2h、油淬）+（580℃、5h、空冷）；达到冲击韧性最大0.723 kgf.m的工艺是（950℃、2h、油淬）+（460℃、1h、空冷）。更多还原

【Abstract】 Multi-aluminum bronze has been widly applied in some area such as machine industry, automobile and plane manufacture, shipbuilding industry and ocean industry because it possesses some super properties, for example mechanical properties wear-resistant, corrosive resistance, oxidation resistance. With the rapid development of modern industry, traditional trademark’s aluminum bronze don’t accord with usefulness request in the certain situation. So, many people who research science are exploiting a new- aluminum bronze and our team are researching a new- aluminum bronze that possesses high strength, high hardness and is made with die. In this paper the effect of as-cast microstructure on mechanical properties of multi-aluminum bronze, the transformation of microstructure of multi-aluminum bronze with homogenizing annealing were studied and optimizing technics of heat treatment. The results shows as following:1.The as-cast microstructure of multi-aluminum bronze are a phase,B ’ phase, Y 2 phase and K phase. There are imbalance phases and supersaturational insoluable element and dendrite segregation in the as-cast microstructure, besides those, there are also insoluable element, intermetallic composite, impurities phase, nonmetallic lard on grain boundary. The as-cast of multi-aluminum bronze possesses high strength, high hardness but low toughness. Grain size, content of a phase, distributing of r2 phase ,shape of K phase impact on mechanical properties of as-cast multi-aluminum bronze. Grain size of as-cast multi-aluminum bronze is 0.000475cm, and it make the plasticity and toughness decrease; lack of a phase and coarse Y 2 phase distributing along grain boundary cause the brittleness of alloy. The main function of the K phase is dispersion-strengthening and the coarse flowery K phase deteriorate the mechanical properties of alloy to a certain extent.2.In low temperature homogeneous annealing, microstructure of multi-aluminum bronze are same to it’s as-cast, and the alloy still possesses high strength, high hardness, but toughness has evidently declined trend.3.In a set of experiment that didn’t vary time but temperature , the microstructure transformed most complete than others processes at 980 C homogeneous annealing, but at 950C homogeneous annealing hardness is highest than others.4.In a set of experiment that didn’t vary temperature but time, we found the K phase were easily affected by the heat holding-time. At heating temperature 950 C,holding time 20h, the k phases have completed the homogeneous process from precipitating, growing to splitting, re-assembling,; At heating temperature 950C,holding time 2h, the ( a + Y 2) phase , a phase, y 2 phase have completed the homogeneous process. With increasing holding time, the Y 2 phase become coarse. According data of hardness, at heating temperature 950C .holding time 2h, the hardness arrive at the top.5.The Multi-aluminum bronze which had been oil quenched after holding 950 for 2h then tempered 500 for 5h had the best tensile strength 625MPa, hardness 41.17HRC,toughness 0.713kg f. m. The Multi-aluminum bronze which had been oilquenched after holding 950 for 2h then tempered 460 for Ih had the best toughness 0. 723 kg f. m, which had been oil quenched after holding 950 for 2h then tempered 580 for 5h had the best hardness 45.84HRC.更多还原