Development of High Strength Metallic Materials Controlled for Nanostructure Using Severe Plastic Deformation

(1)为了使金属材料在高压下发生剧烈塑性变形（SPD），本研究建立了高压扭转装置（HPT）。该设备允许在较高温度下使用圆盘型和圆柱形样品。(2)对Al-3%Mg-0.2%Sc合金进行HPT处理。研究了旋转和施加压力对两种试样硬度和显微组织的影响。硬度随旋转和施加压力的增加而增加，但两种类型的试样都存在饱和。试样外缘晶粒尺寸减小至0.15 μm。高温拉伸试验表明，盘状试样的超塑性伸长率为~ 500%，圆柱形试样的超塑性伸长率为~ 1600%。(3)镁合金在150℃高温热处理后，晶粒尺寸由22 μm减小到0.22 μm，在200℃高温下的超塑性伸长率为~ 620%，应变率为3.3 × 10^<-3> s^<-1>。(4)碳钢经高温高温热处理后，圆盘试样外缘硬度显著提高。这种趋势不同于铝合金和镁合金。HPT试样的抗拉强度为1.2 GPa。(5)采用等通道角压（ECA）对时效硬化铝合金进行SPD处理。经ECAP处理的合金在100℃时效后，硬度和均匀伸长率均有提高。SPD试样在较低温度下进行时效处理，强度和延展性都有很大的提高潜力。

(1)In this study, a facility for high pressure torsion (HPT) was established in order to impose severe plastic deformation (SPD) on metallic materials under high pressure. This facility permits use of disk-type and cylindrical type of specimens at elevated temperatures for the former type of specimens.(2)HPT was conducted on an Al-3%Mg-0.2%Sc alloy. The effect of rotation and imposed pressure on the hardness and microstructure was examined for both types of specimens. The hardness increased with an increase in rotation and applied pressure but there was a saturation of both types of specimens. The grain size was reduced to 0.15 μm at the outer edges of the specimens. Tensile tests at high temperatures revealed superplastic elongation, of 〜500% for the disk specimens and 〜1600% for the cylindrical specimens.(3)HPT at 150℃ for Mg alloys showed that the grain size was reduced from 22 μm to 0.22 μm which then resulted in a superplastic elongation of 〜620% at 200℃ with a strain rate of 3.3x10^<-3> s^<-1>.(4)A carbon steel processed by HPT exhibited an significant increase in hardness at outer edges of the disk specimens. This trend was different from Al alloys and Mg alloys. Tensile strength of 1.2 GPa was attained from the HPT specimens.(5)Age-hardenable Al alloys were subjected to SPD through equal-channel angular pressing (ECA). Aging at 100℃ for the ECAP processed alloys led to an increase in hardness and also an increase in uniform elongation There was a great potential for an increase in both strength and ductility when SPD specimens are subjected to aging treatment at lower temperatures.