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首页> 美国政府科技报告 >Production of Dense Compact Billet From Ti-Alloy Powder Using Equal Channel Angular Extrusion.
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Production of Dense Compact Billet From Ti-Alloy Powder Using Equal Channel Angular Extrusion.

机译：用等通道角挤压法生产Ti合金粉末致密致密坯料。

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摘要

The project was aimed at an investigation of the potential for cost-effective, efficient consolidation of pre-alloyed 'PA' Ti-6Al-4V (HDH) powder at temperatures of 400 deg C and below using Equal Channel Angular Extrusion (ECAE), with applied back pressure. The limit on processing temperature was imposed to minimize the contamination of powder and compact with gaseous constituents known to be harmful to resultant properties. An analysis of existing published investigations of current processing techniques, most notably those involving hot isostatic pressing (HIP), reveals that relative densities of 98-100% can only be obtained at processing temperatures in excess of 800C. For such methods, and temperatures below 400 deg C, the relative densities achievable are typically of the order of 77%, when starting with an initial 'tape' density of 63%. In this context, the project goals, of reducing the processing temperature of PA powder compaction below 400 deg C while achieving a relative density above 98%, are to be seen as quite challenging. The novelty of the approach arises from the notion that severe shear deformation could prove an important factor for improving consolidation at relatively low processing temperatures. It has been shown that the use of ECAE with back pressure at 400C permits production of compacts with relative densities in the range 98.3-98.6% and green strengths up to 750 MPa. The improvements in density and green strength are attributed to enhancement of self-diffusion rates at low temperatures that are in turn the result of an excess of structural defects created during severe shear deformation and the effects of imposed hydrostatic pressure (back pressure).

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