以即時中子研究CoCrFeMnNi等莫耳高熵合金疲勞行為

Abstract

鈷鉻鐵錳鎳等莫爾高熵合金在常溫常壓下為單一面心立方材料，也是目前所知擁有最高韌性之材料，本研究藉由即時中子繞射實驗研究鈷鉻鐵錳鎳五元等莫耳高熵合金在拉伸及循環應力下的塑變形為差異。藉由比較鈷鉻鐵鎳及鈷鉻鐵錳鎳高熵合金室溫之拉伸性質以研究錳的添加對高熵合金的影響，本研究發現錳的添加雖使降伏強度及最大拉伸強度上升，但同時也降低合金的伸長率；另外，鑄造態合金所擁有之大晶粒使得鈷鉻鐵鎳及鈷鉻鐵錳鎳兩合金在室溫下便觀察到雙晶對其塑性變形的影響。在低週疲勞實驗中，差排、雙晶及差排牆間的互動主宰了鈷鉻鐵錳鎳等莫爾高熵合金之疲勞行為。

Equiatomic CoCrFeMnNi high entropy alloy(HEA) is single phase FCC material under room temperature and pressure, also known as the material with highest toughness. This research aims to investigate a five-element HEA CoCrFeMnNi plastic deformation behavior under tensile and cyclic stress by using in-situ neutron diffraction. Then compare the tensile properties at room temperature between CoCrFeNi and CoCrFeMnNi in order to study the effect of adding manganese to HEA. The result shows the addition of manganese increases yield strength and ultimate tensile strength, but at the same time decreases the HEA elongation. Besides, the large grains in as-cast alloy allows the observation of the effect of twinning on plastic deformations of both HEA, CoCrFeNi and CoCrFeMnNi at room temperature. In low cycle fatigue experiment, the interaction between dislocation, twinning and dislocation wall dominates the fatigue behavior of CoCrFeMnNi.