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微细晶粒超塑性通常只有当合金在高温下的变形过程中能保持接近等轴而稳定的超细晶粒时才能实现。本文介绍了金属材料在高温下加热时晶粒长大的普遍规律,特别着重阐明利用适当尺寸和体积分数的第二相粒子来稳定材料基体的超细晶粒的基本原理。用第二相粒子来稳定材料的超细晶粒时,除要求第二相粒子应有适当的尺寸和体积分数外,还要求第二相粒子在高温下的超塑变形过程中不会迅速粗化,这就要求组成第二相粒子的合金元素在基体中应具有低的固溶度和低的扩散系数。晚近国外发展出的,用 ZrAl_3粒子来稳定铝基固溶体超细晶粒的超塑铝合金,就是应用这种原理的极好例子。
Fine grain superplasticity is usually achieved only when the alloy is maintained near equiaxed and stable ultra-fine grains during deformation at high temperatures. In this paper, the general rule of grain growth when the metal material is heated at high temperature is introduced. Particular emphasis is placed on the basic principle of stabilizing the ultrafine grain of the material matrix by using the second phase particles of suitable size and volume fraction. The use of second-phase particles to stabilize the ultra-fine grains of the material requires that the second-phase particles, in addition to being of suitable size and volume fraction, require that the second-phase particles do not rapidly grow during superplastic deformation at elevated temperatures This requires that the alloying elements that make up the second-phase particles should have a low solubility in solids and a low diffusion coefficient in the matrix. Recently developed abroad, the use of ZrAl_3 particles to stabilize ultra-fine grain aluminum-based solid solution super-alloy aluminum alloy is an excellent example of the application of this principle.