Experimental evaluation of the plane stress fracture toughness for ultra-fine grained aluminum specimens prepared by accumulative roll bonding process
Experimental evaluation of the plane stress fracture toughness for ultra-fine grained aluminum specimens prepared by accumulative roll bonding process
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DOI：
10.1016/j.msea.2017.09.085
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发表时间：
2017-12
期刊：
影响因子：
6.4
通讯作者：
D. Rahmatabadi;R. Hashemi;B. Mohammadi;T. Shojaee
中科院分区：
文献类型：
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作者：
D. Rahmatabadi;R. Hashemi;B. Mohammadi;T. Shojaee
在这项研究中，首次研究了通过累积轧制工艺生产的超细晶粒铝试样的平面应力断裂韧性。在室温下，在不使用润滑剂的情况下，通过 ARB 工艺成功生产了多达 7 个周期的样品，每个周期的厚度减少了 50%。使用 ASTM E561 标准和紧凑拉伸样品评估退火和不同 ARB 循环的断裂韧性。此外，还通过单轴拉伸试验、显微硬度测量、扫描电子显微镜和 X 射线衍射评估了超细晶粒铝 ARBed 样品的机械性能、拉伸断裂面和晶粒尺寸。通过增加ARB循环次数，断裂韧性得到提高，并且该参数在最后一个循环中达到最大值，约为25.4 MPam1/2，比退火样品提高了155%。 X 射线衍射结果表明，通过增加 ARB 循环次数，微晶尺寸减小，第 7 个循环 ARBed 样品的微晶尺寸从退火样品的 1341 nm 达到 175 nm。此外，通过将 ARB 循环次数增加到第 7 次循环，超细晶粒铝的拉伸强度和显微硬度分别增加到 232 MPa 和 51VHN。伸长率值先减小后增大。 SEM结果表明，退火态试样中出现大韧窝的韧性断裂模式，经过ARB处理后，转变为具有细长二次剪切和细韧窝的剪切韧性断裂。
In this research, the plane stress fracture toughness of ultra-fine grained aluminum specimens produced through accumulative roll bonding (ARB) process was investigated for the first time. The specimens were produced successfully by the ARB process up to 7 cycles with the amount of 50% thickness reduction in each cycle at room temperature without using lubricant. The fracture toughness was evaluated for the annealed and different ARB cycles using ASTM E561 standard and compact tension specimens. Additionally, mechanical properties, tensile fracture surfaces and crystallite size of ultra-fine grained aluminum ARBed specimens were evaluated by uniaxial tensile tests, microhardness measurements, scanning electron microscopy and X-ray diffraction. By increasing the number of the ARB cycles, fracture toughness was increased and the maximum value of this parameter was achieved in the last cycle, which was approximately 25.4 MPam1/2that it increased by 155% higher than the annealed specimen. Results of X-ray diffraction demonstrated that by increasing the number of the ARB cycles, crystallite size decreased so that it reached 175 nm for the 7th cycle ARBed specimen from 1341 nm for annealed samples. Furthermore, by increasing the number of the ARB cycles up to the 7th cycle, tensile strength and microhardness of ultra-fine grained aluminum increased to 232 MPa and 51VHN, respectively. At first, the value of elongation decreased and then increased. The SEM results showed that ductile fracture mode with large dimples occurring in the annealed specimen, changed to shear ductile fracture with elongated sophomoric shear and fine dimples after the ARB process.