Abstract: Equal-channel angular pressing was conducted on a 7475 aluminum alloy at temperature from room temperature to 773K up to an equivalent true strain of 12. The grain refinement limit was dependent upon the precise pressing temperature, and the grain was refined to within the range from 0.29 to 1.9μm by ECAP at these different temperatures. At higher temperature, it is apparent that these precipitates may be important in pinning the grain boundaries and thus increasing the thermal stability of the sub-micrometer-grained structure.
Microstructure and grain refinement limit of 7475 aluminum alloy after equal-channel angular pressing
Abstract:
Equal-channel angular pressing was conducted on a 7475 aluminum alloy at temperature from room temperature to 773 K up to an equivalent true strain of 12. The grain refinement limit was dependent upon the precise pressing temperature, and the grain was refined to within the range from 0.29 to 1.9 μm by ECAP at these different temperatures. At higher temperature, it is apparent that these precipitates may be important in pinning the grain boundaries and thus increasing the thermal stability of the sub-micrometer-grained structure.
图1 7475铝合金在273 K经C方式ECAP 5道次后 的典型微观组织和选区电子衍射谱 Fig.1 Typical microstructure and SAED pattern for 7475 aluminum alloy after ECAPed at 273 K for 5 passes using route C
图2 7475铝合金在523 K经BC方式ECAP 12道次后 的典型微观组织和选区电子衍射谱 Fig.2 Typical microstructure and SAED pattern for 7475 aluminum alloy after ECAPed at 523 K for 12 passes using route BC
图3 7475铝合金在523 K经BC方式ECAP 12道次后的典型沉淀相组织 Fig.3 Typical bright(a) and dark field(b) images showing distribution of precipitates in 7475 aluminum alloy after ECAPed at 523 K for 12 passes using route BC
图4 7475铝合金在573 K经BC方式ECAP 12道次后的典型组织及选区衍射谱 Fig.4 Typical microstructure and SAED pattern(a) and sub-micrometer-grained structure(b) for 7475 aluminum alloy after ECAPed at 573 K for 12 passes using route BC
图5 7475铝合金在573 K经BC方式 ECAP 12道次后的沉淀相分布 Fig.5 Distribution of precipitates after ECAPed at 573 K for 12 passes using route BC
图6 7475铝合金在773 K经BC方式 ECAP12道次后的典型组织 Fig.6 Typical microstructure after ECAPed at 773 K for 5 passes using route BC
图7 7475铝合金ECAP后亚微晶晶粒尺寸 与变形道次的关系 Fig.7 Relation between average grain size and ECAP passes for 7475 aluminum after ECAPed at 523 and 573 K using route BC
图8 7475铝合金在523, 573, 773 K下经BC方式 ECAP后晶粒细化极限与温度的关系 Fig.8 Relation of grain size limit with temperature for 7475 aluminum after ECAPed at 523, 573 and 773 K using route BC