Improvement of strength of B／Al composite by thermal-mechanical cycling

The mechanical properties of B/Al composite were measured at room temperature in the as-fabricated condition and after thermal-mechanical cycling(TMC). The effects of TMC on microstructure and tensile fracture behavior of B/Al composite were studied using transmission electron microscope(TEM) and scanning electron microscope(SEM). The fibers/matrix interfaces are degraded during TMC, the extent of which is enhanced with increasing the cycles, causing a measurable decrease of stage I modulus of the B/Al composite. The TMC induces the dislocation generation in the aluminum matrix and the dislocation density increases with the cycles. The synergistic effect of the matrix strengthening and the interracial degradation during TMC is found to play an important role in controlling the changes of tensile strengths and fracture behavior of the composite. The ultimate tensile strength of the composite increases with the cycles increasing. The interfaces in the B/Al composite change from the stronglybonded states toward the appropriately-bonded ones with increasing the cycles. TMC will provide an approach of improving the strength of B/Al composites.     

Effect of homogenization treatment in electric field on microstructure and properties of 1420 Al-Li alloy

0　ＩＮＴＲＯＤＵＣＴＩＯＮＢｙｖｉｒｔｕｅｏｆｔｈｅｉｒｌｏｗｄｅｎｓｉｔｙ ,ｈｉｇｈｓｔｒｅｎｇｔｈ/ｗｅｉｇｈｔｒａｔｉｏ ,ｈｉｇｈｍｏｄｕｌｕｓａｎｄｈｉｇｈｃｏｒｒｏｓｉｏｎａｎｄｆａｔｉｇｕｅｒｅｓｉｓ ｔａｎｃｅ ,Ａｌ Ｌｉａｌｌｏｙｈａｓｂｅｅｎｄｅｖｅｌｏｐｅｄａｓｓｔｒｕｃｔｕｒｅｍａｔｅｒｉ ａｌｆｏｒａｉｒｃｒａｆｔａｎｄｓｐａｃｅｃｒａｆｔ[1～ 3] .Ｂｕｔｉｔｉｓｄｉｆｆｉｃｕｌｔｆｏｒｃｏｎｖｅｎｔｉｏｎａｌｈｅａｔ ｔｒｅａｔｍｅｎｔｔｅｃｈｎｏｌｏｇｙｔｏｆｕｒｔｈｅｒ…     

真空热循环对单向M40J/5228A复合材料质损率和线膨胀系数的影响

对单向M40J/5228A复合材料进行了真空热循环试验 ( 93~413 K,10-5Pa)。分别测试了经不同次数真空热循环后材料的质损率及线膨胀系数。通过所建二维细观损伤模型分析了真空热循环次数对材料线膨胀系数曲线影响的原因。试验结果表明,随真空热循环次数的增加,质损率增大,并经约48次真空热循环后趋于平缓;横向线膨胀系数随温度升高而线性增大,真空热循环次数对其没有影响;纵向线膨胀系数在原始状态时随温度升高而线性减小,经113次真空热循环后表现出先下降后上升的非线性特征,真空热循环次数对纵向线膨胀系数的影响,与界面脱粘程度和残余应力的消除密切相关。      

热机械循环对B/Al复合材料拉伸性能及显微结构的影响

热机械循环是复合材料所面临的苛刻空间环境因素.对B/Al复合材料进行温度变化范围为-125～125℃,外加拉伸载荷为30MPa的热机械循环试验,通过室温拉伸试验测量了B/Al复合材料的拉伸性能,利用SEM及TEM分析了复合材料的拉伸断口形貌及显微结构,研究了热机械循环对B/Al复合材料拉伸性能及显微结构的影响.研究表明,热机械循环造成了B纤维与Al基体之间界面的弱化,产生了可测的弹性模量的降低;同时,引起基体塑性应变,造成基体内位错密度增加.在热机械循环初期,B/Al复合材料的抗拉强度是增加的,但随即随热机械循环周次的增加而下降.     

Effect of aging in an electric field on microstructures and properties of 1420 Al-Li alloy

0　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｏｕｇｈｉｔｓｓｔｒｅｎｇｔｈｉｓｎｏｔｖｅｒｙｈｉｇｈ ,ｔｈｅ 14 2 0Ａｌ -Ｌｉａｌｌｏｙｈａｓｍａｎｙａｄｖａｎｔａｇｅｓｓｕｃｈａｓｂｅｔｔｅｒｐｌａｓｔｉｃｉｔｙ ,ｌｏｗｅｒｄｅｎｓｉｔｙａｎｄｉｔｃａｎｗｏｒｋｕｎｄｅｒｃｏｒｒｏｓｉｖｅａｎｄｌｏｗｔｅｍ ｐｅｒａｔｕｒｅｃｏｎｄｉｔｉｏｎｓ[1] .Ｍｕｃｈｅｆｆｏｒｔｈａｓｂｅｅｎｄｅｖｏｔｅｄｏｎｉｍｐｒｏｖｉｎｇｔｈｅｐｒｏｐｅｒｔｉｅｓｏｆｔｈｅ 14 2 0Ａｌ -Ｌｉａｌｌｏｙ ,ｓｏｉｔｉｓｄｉｆｆｉｃｕ…