(1. 青海大學(xué) 金屬材料研究所，西寧 810016；
2. 哈爾濱工業(yè)大學(xué) 材料科學(xué)與工程學(xué)院，哈爾濱 150001)
摘 要: 對35%(體積分?jǐn)?shù))的Mg2B2O5w/AZ31復(fù)合材料分別在外加應(yīng)力為7、14、21和42 MPa時進(jìn)行加載熱循環(huán)實(shí)驗(yàn)，研究其蠕變行為。結(jié)果表明：加載熱循環(huán)分為初始蠕變階段、穩(wěn)定蠕變階段和失穩(wěn)變形階段；外加載荷為42 MPa時，熱循環(huán)由穩(wěn)定蠕變階段迅速進(jìn)入失穩(wěn)變形階段；當(dāng)外加載荷為21 MPa時，應(yīng)變速率的急劇變化對累積殘余應(yīng)變影響較小；熱循環(huán)滯后環(huán)傾角隨外加載荷的增大而減小；Mg2B2O5w/AZ31復(fù)合材料的外加載荷越低，應(yīng)變速率敏感指數(shù)越高，而在400 ℃的高溫蠕變雖也呈現(xiàn)超塑性行為，但應(yīng)變速率比加載熱循環(huán)大幅下降。在加載熱循環(huán)過程中，300 ℃時基體中的平均內(nèi)應(yīng)力接近于零，熱循環(huán)殘余應(yīng)變的產(chǎn)生主要發(fā)生在熱循環(huán)的高溫階段。
關(guān)鍵字: 鎂基復(fù)合材料；硼酸鎂晶須；熱循環(huán)；超塑性；應(yīng)變速率
（1. Institute of Metal Research, Qinghai University, Xining 810016, China;
2. School of Materials Science and Technology Engineering, Harbin Institute of Technology, Harbin 150001, China）
Abstract:The creep behavior of the 35% (volume fraction) Mg2B2O5w reinforced AZ31 magnesium matrix composites was investigated under thermal cycling conditions with varied external applied stresses of 7, 14, 21 and 42 MPa, respectively. The results show that the creep behavior of Mg2B2O5w/AZ31 under the thermal cycling with external applied stress is primary creep stage at first, followed by steady creep stage and finally unsteady and quick creep. The composite sample subjected to thermal cycling and applied stress of 42 MPa occurs an unsteady and quick creep after a shortly steady creep. The drastic fluctuation of strain rates has less effect on the strain increment trend when the composite sample subjected to thermal cycling and applied stress of 21 MPa. The tilt angles of hysteresis loops decrease with increasing the applied stresses. The lower the applied stress is, the higher the strain rate sensitivity exponent m is. Superplasticity behavior also occurs for the composite isothermal creep experiment at 400℃. However, the strain rate of the composite isothermal creep is much lower than that of the composites creeps when the composite samples are subjected to thermal cycling and applied stresses. The average thermal residual stress in the matrix Mg alloy approaches null at elevated temperature of about 300 ℃. The residual strains mainly appear at upper temperature during the heating of cycling.
Key words: Mg based composites; Mg2B2O5 whisker; thermal cycling; superplasticity; strain rate
