HIGH TEMPERATURE DEFORMATION OF POLYCRYSTALS WITH FEW EQUIVALENT SLIP SYSTEMS

研究了镁铝固溶体的高温塑性变形行为。材料是一种主要滑移系少于5个的模型，即多晶体塑性变形所需的最少独立滑移系。在两个温度范围内，应变速率的温度依赖性是不同的。在不同的温度范围内，应变率的应力依赖关系也不同。在较低的温度范围内，观察到应变速率的应力依赖性不同的两个应力范围之间的逐渐变化。对形变后位错结构的电子显微镜观察表明，位错的Burgers矢量在不同的温度范围内是不同的。A位错和a c位错分别在较低和较高温度范围内观察到。在较低温度下位错形状的变化在…范围内进一步的研究表明，不同滑动面上溶质气氛位错的分离应力是不同的。基于该模型的晶体结构、滑移面和扩散各向异性的数值模拟，定量地证明了实验得到的高温变形行为的转变条件。实验还确定了应力方向对织构较强的镁铝合金蠕变行为转变的影响。结果表明，在较低的温度下，两个应力范围之间的渐变是位错从溶质环境中逐渐脱离的结果，多晶固溶体的宏观变形方面与立方固溶体不同，多晶固溶体具有较少的等效一次滑移系。这是由于不同滑移面上的溶质原子与位错相互作用的差异造成的。较少

High temperature plastic deformation behavior of magnesium-aluminum solid solutions has been investigated. The materials are a model whose primary slip systems are fewer than five,i.e. the least number of independent slip systems required for plastic deformation of polycrystals. There are two temperature-ranges where the temperature dependence of strain rate is different. The stress dependence of strain rate is also different in each temperature range. Gradual change between two stress-ranges, where the stress dependence of strain rate is different, was observed at lower temperature range. The differences of concentration dependence are also observed at each stress and temperature range.TEM observations of the dislocation structures after deformation show that the burgers vector of dislocations differ at each temperature range. The a and a+c dislocations are mainly observed at lower and higher temperature range, respectively. The change in shape of dislocations at lower temperature ran … More ge suggests that the break-away stresses of dislocations from solute atmosphere on different slip planes are different from each other. The transition conditions of high temperature deformation behavior, obtained by experiments, are proved quantitatively by means of the numerical simulations of dragging force and solute distribution based on the model including crystalline structure, slip plane and anisotropy of diffusion. The effects of stressing direction on the transition of creep behavior of magnesium-aluminum-alloys, which have strong texture, are also determined experimentally. It is concluded that the gradual change between two stress-ranges at lower temperature is caused by the gradual break-away of dislocations from solute atmosphere.As a conclusion, the aspects of macroscopic deformation of polycrystalline solid solutions, which have few numbers of equivalent primary slip systems, are different from that of cubic solid solutions. It is caused by the difference of interactions between solute atoms and dislocations on different slip planes. Less