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151.
R.K Mahidhara 《Journal of Materials Engineering and Performance》1995,4(6):674-678
Specimens of a super plastic 7475 aluminum alloy with grain sizes ranging between 9 and 35 |xm were tensile tested at a strain
rate of 1 × 10
- 4/s at 457 and 517 °C. At 517 °C, the ductility was found to decrease with an increase in grain size. At 457 °C, on the other
hand, the ductility was found to increase initially and then decrease for grain sizes larger than 14 μm. The latter decrease
in ductility is attributed to the lowered ability for grain- boundary sliding with decreasing grain- boundary area. In the
as- received material (grain size of 9 μm), the observed low ductility is attributed to an inhomogeneous microstructure. 相似文献
152.
用挤压铸造法制成SiC_w/LD2复合材料,在470℃下进行热挤压得到板材,挤压比为1:22.在570℃进行超塑拉伸实验,拉伸速度由1mm/min逐步升至5mm/min时获得了最大延伸率280%.用X射线衍射法对超塑拉伸过程中基体和晶须的织构变化进行了研究.结果表明,在超塑拉伸过程中基体的织构要发生漫散,同时有再结晶织构出现,这种再结晶织构也会随拉伸的进行而漫散.晶须在拉伸过程中要发生转动,这种转动主要是θ转动,基本上不发生ω转动. 相似文献
153.
154.
1 INTRODUCTIONRecently , the use of magnesium alloys asstructural materials has significantlyincreased,forits good damping capacity , di mension stability ,machinability and lowcasting costs . But magnesi-umalloys normally exhibit lowductility near roomtemperature because of their HCP structure .Therefore ,it is necessary to i mprove the ductilityof these alloys for their use as structural compo-nents[1 3].In manufacturing,superplastic forming is of-ten combined with diffusion bonding, w… 相似文献
155.
研究了镁基复合材料超塑性变形过程中SiC晶须织构的演化规律,并分析了其对孔洞行为的影响。超塑性拉伸试验在613K~723K,8.3×10-4s-1~8.3×10-2s-1条件下进行。在613K,1.67×10-2s-1初始应变速率下,获得了200%的延伸率。SiC晶须在超塑性变形过程中发展出强烈的<111>//ED纤维织构。SiC晶须的这种取向对晶界滑动有阻碍作用,不仅使孔洞易于萌生,也加速了其长大与连接。 相似文献
156.
157.
Peter N. Comley 《Journal of Materials Engineering and Performance》2004,13(6):660-664
Superplastic forming (SPF) of Ti-6Al-4V has traditionally been performed at 900 °C. Although SPF equipment and dies have been
developed to withstand this high temperature, their life is limited and maintenance is high. In addition, the formed sheets
need chemical milling after processing to remove a significant layer of alpha case, and parts require hand polishing due to
a rough die surface caused by high temperature oxidation. The recent development of a Ti-6Al-4V alloy with a grain size of
around 1 μm has led to the possibility of superplastic forming at a much lower temperature than regular Ti-6Al-4V. In addition,
the forming speed can be increased. This work looks at some of the SPF attributes of fine-grain titanium, in particular, the
optimum forming temperature, the thinning characteristics, alpha case formation, and forming speeds. The authors also address
manufacturing advantages, such as die life, equipment needs, and operator comfort. Some prototype and preproduction aircraft
components on Boeing airplanes are presented. The results show that the new fine-grain material could significantly lower
the cost of SPF Ti-6Al-4V part production for the aerospace industry.
This paper was presented at the International Symposium on Superplasticity and Superplastic Forming, sponsored by the Manufacturing
Critical Sector at the ASM International AeroMat 2004 Conference and Exposition, June 8–9, 2004, in Seattle, WA. The symposium
was organized by Daniel G. Sanders, The Boeing Company. 相似文献
158.
本文用密栅云纹实验法显示和观测了具有应变速率强化效应与应变强化效应材料的应变产生、发展及传播过程,并对两种强化效应传播应变的能力进行了分析比较。 相似文献
159.
通过高温拉伸实验研究TC18钛合金在温度为720~950℃,初始应变速率为6.7×10~(-5)~3.3×10~(-1)s~(-1)时的超塑性拉伸行为和变形机制。结果表明:TC18钛合金在最佳超塑性变形条件下(890℃,3.3×10~(-4)s~(-1)),最大伸长率为470%,峰值应力为17.93MPa,晶粒大小均匀。在相变点Tβ(872℃)以下拉伸,伸长率先升高后下降,在温度为830℃,初始应变速率为3.3×10~(-4)s~(-1)时取得极大值373%,峰值应力为31.45MPa。TC18钛合金在两相区的超塑性变形机制为晶粒转动与晶界滑移,变形协调机制为晶内位错滑移与攀移;在单相区的超塑性变形机制为晶内位错运动,变形协调机制为动态回复和动态再结晶。 相似文献
160.
Superplastic behaviors of quasicrystal phase containing Mg-5.8Zn-1Y-0.48Zr alloy sheets fabricated by combination of extrusion and hot-rolling processes have been investigated at temperature ranging from 623 to 753 K and at the strain rates ranging from 10-4 to 10-2 s-1 by uniaxial tensile tests. An excellent superplasticity with the maximum elongation to failure of 1020% was obtained at 753 K and the strain rate of 1.04×10-3 s-1 and its strain rate sensitivity, m, is as high as up to 0.75. The microstructure was stable during superplastic deformation due to the uniformly distributed fine quasicrystal particles. In addition, micro-cavities and their coalescences were observed in the superplastic deformation of the ZW61 magnesium alloy. Grain boundary sliding (GBS) was considered to be the main deformation mechanism during the superplastic deformation. Dislocation creep controlled by atom diffusion through grain boundaries or interior grains is suggested mainly to accommodate the GBS in super-plastic deformation. 相似文献