CTO/PCL-3057共混软段聚氨酯弹性体的相分离和力学性能

以蓖麻油(CTO)/聚己内酯三醇(PCL-3057)共混物为软段,三羟甲基丙烷为小分子交联剂,与多亚甲基多苯基多异氰酸酯(PAPI)反应,制备了软段中CTO质量分数分别为30%、50%、60%、70%和100%的聚氨酯弹性体(PUE),研究软段组成对PUE相分离结构和力学性能的影响。结果表明:CTO主要促进硬段之间氢键的形成,PCL-3057主要促进软硬段之间氢键的形成;两者各占50%时,PUE结晶性好,氢键度大,微相分离程度较完善,交联程度适当,所以力学强度高且韧性好。CTO柔顺性好,可以降低PUE软段的玻璃化转变温度(T_(gs)),而PCL-3057中极性基团过多会降低T_(gs);两者各占50%时,T_(gs)最大。PCL-3057都能显著提高PUE的动态力学性能。

Deformation and heat treatment ability of three-layer 6009/7050/6009 Al alloy clad slab prepared by direct-chill casting

Three-layer6009/7050/6009aluminum alloy clad slab was fabricated by an innovative direct-chill casting process.To study the response of the clad slab to plastic deformation and heat treatments,homogenization annealing,hot rolling,solution and aging were successively performed on the as-cast6009/7050/6009clad samples.The results revealed that excellent metallurgical bonding between7050alloy layer and6009alloy layer was achieved under optimal parameters.The clad ratio obviously decreased when the annealed sample was rolled to55%hot reduction level,and then changed slightly with further rolling.Furthermore,the content of rodlike Zn-rich phases increased significantly in7050alloy layer in the homogenized clad samples after rolling at55%,65%and75%hot reduction levels,and the higher level of hot reduction resulted in narrower diffusion layer.Subsequent solution and aging significantly improved the hardness in7050alloy layer,interfaces and6009alloy layers of the rolled samples except for the thin side for the75%hot reduction sample.

喷丸强化与固溶强化复合处理对2024铝合金耐蚀性能的影响

研究了喷丸强化、固溶强化、喷丸强化+固溶强化3种工艺对初始时效态2024铝合金耐盐雾腐蚀性能的影响。结果表明,原始试样组织内存在大量第二相颗粒,颗粒尺寸最长约为83μm。经固溶处理后,部分第二颗粒溶解于基体,剩余颗粒尺寸减小至17μm。采用喷丸强化和固溶强化复合处理后,材料近表面组织的第二相颗粒几乎全部溶解。当盐雾腐蚀时间为3 h时,原始试样的腐蚀坑直径约为?90μm,喷丸+固溶强化试样的腐蚀坑直径约为?50μm;喷丸试样的腐蚀深度约为38.75μm,而喷丸+固溶强化试样的腐蚀深度降低至12.5μm。这表明喷丸强化和固溶强化复合处理有助于第二相颗粒的溶解,改善材料组织和成分的均匀性,进而提升铝合金的耐蚀性能。

AlCr_(1.3)TiNi_(2)共晶高熵合金的高温摩擦学性能及磨损机理

采用电磁悬浮熔炼+直接铸造的方法制备了千克级的AlCr_(1.3)TiNi_(2)共晶高熵合金,借助TEM、APT等表征手段分析了该合金的微观组织与成分分布,使用HT-1000摩擦试验机对比研究了该合金与GH4169镍基高温合金的高温摩擦学性能。结果表明:该共晶高熵合金具有超细的层片状共晶组织(层片间距约350 nm),其共晶两相为晶格错配度只有约2%的bcc相与L2_(1)相,L2_(1)相中还存在大量的纳米析出相;≤600℃时,共晶高熵合金的磨损机理以磨粒磨损为主,其磨损率均低于GH4169合金;800℃时,共晶高熵合金的磨痕表面塑性变形加剧,其摩擦系数明显高于GH4169合金,但2者的磨损率相差不大。GH4169合金高温耐磨性的提高得益于其磨损表面氧化物膜的形成,而共晶高熵合金出色的耐磨性主要与其良好的高温组织稳定性及力学性能有关。