(1. 重慶大學(xué) 材料科學(xué)與工程學(xué)院, 重慶 400045；
2. 重慶大學(xué) 國(guó)家鎂合金材料工程技術(shù)中心, 重慶 400045)
摘 要: 在不同溫度下，采用雙向雙通道變通徑擠壓(DDE)對(duì)AZ31鎂合金進(jìn)行擠壓，研究該工藝對(duì)其組織、力學(xué)性能、拉壓不對(duì)稱性和斷裂行為的影響。結(jié)果表明：與均勻態(tài)AZ31鎂合金相比，擠壓后所得試樣的晶粒顯著細(xì)化，力學(xué)性能和拉壓不對(duì)稱性得到改善；與采用等通道角擠壓工藝多道次擠壓試樣的力學(xué)性能相比，該工藝具有一定的優(yōu)勢(shì)。此外，隨著擠壓溫度的升高，晶粒尺寸逐漸增大，顯微硬度、抗拉強(qiáng)度和壓縮率逐漸降低。從250 ℃到450 ℃，晶粒尺寸從6 μm增大到26 μm，硬度值(HV)從67降低到56，抗壓強(qiáng)度從400 MPa降低到343MPa，壓縮率從14.8%降低到9.7%。均勻態(tài)AZ31和擠壓態(tài)AZ31的壓縮斷口均為穿晶斷裂，前者斷裂機(jī)理為脆性解理斷裂，后者為韌脆結(jié)合型準(zhǔn)解理斷裂。
關(guān)鍵字: AZ31鎂合金；雙向雙通道變通徑擠壓；顯微組織；力學(xué)性能；斷裂行為
（1. College of Materials Science and Engineering, Chongqing University, Chongqing 400045, China;
2. National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400045, China）
Abstract:The AZ31 magnesium alloy was extruded by dual-directional extrusion (DDE) at different temperatures. Then, the microstructures, mechanical properties, tension and compression asymmetry and the rupture behaviors were studied. The results indicate that, compared with homogenized samples, the grain sizes of the extruded ones are all refined, thereby improving the mechanical properties and tension and compression asymmetry. The improved mechanical properties are comparable or even superior to those of the alloys subjected to the equal-channel angular extrusion several passes. Further more, with the increase of extrusion temperature from 250 to 450 ℃, the grain size increases from 6 to 26 μm, and the microhardness, ultimate compressive strength(UCS) and compressive ratio decrease from 67 to 56(HV), 400 to 343 MPa, 14.8% to 9.7%, respectively. The microstructures of fracture show that both homogenized and as-extruded AZ31 alloys cut through the grains, while the fracture mechanism of homogenized AZ31 and as-extruded AZ31 are brittle cleavage fracture and ductile-brittle quasi-cleavage fracture, respectively.
Key words: AZ31 magnesium alloy; dual-directional extrusion; microstructure; mechanical property; rupture behavior
