Al-Si合金/高钙粉煤灰基高温相变蓄热球的制备及应用性能

以高钙粉煤灰为基体材料,Al-Si共晶合金粉为相变介质,利用干压成型及混合烧结法制备了直径为15 mm蓄热球,研究了成型压力及合金粉含量对蓄热球综合性能的影响,并对其堆积承载高度及性价比进行了估算和分析。结果表明:相同成型压力下,合金粉含量越高,蓄热球的相变潜热、密度及开裂载荷越高。合金粉含量相同时,蓄热球密度及开裂载荷随成型压力的增大而增大,而相变潜热基本不受成型压力影响。蓄热球相变潜热越高其熔化功率越大,说明其相对导热性能越好,而密度对熔化功率影响不大。以单个蓄热球常温下开裂载荷的大小作为堆积体底层接触力的理论峰值,估算出对应的最大理论堆积高度范围为47.7~287.2 m,而蓄热球在高温下的堆积高度均不小于20 m。利用层次分析法(AHP)对蓄热球进行综合性价比分析,当合金粉含量为40%,成型压力为8 MPa时,蓄热球综合应用性价比较优。

Microstructure and compressive deformation of hypereutectic Al-Si-Fe based P/M alloys fabricated by spark plasma sintering

Al-Si-Fe based alloys are attractive light-weight structural materials for automotive engine components because of their high wear resistance, low density and low thermal expansion. Al-17Si 5Fe-2Cu-lMg-lNi-lZr alloys were produced in compact form by a spark plasma sintering （SPS） technique using gas atomized powders. The mean grain size of the compact was 530 nm, and fine equiaxed grains and uniformly distributed precipitates were observed in the compact. The compressive deformation behavior of the SPSed materials was examined at various temperatures and strain rates. All the true stress-true strain curves showed steady state flow after reaching peak stress. The peak stress decreased with increasing test temperature and decreasing strain rate. In the deformed specimens, the equiaxed grain morphology and the dislocation microstructure within the equiaxed grains were observed. These facts strongly indicated the occurrence of dynamic recrystallization during high temperature deformation of the present alloy.

AZ91D镁合金表面激光熔覆Al-Si合金涂层

用Nd:YAG脉冲激光器在镁合金AZ91D表面激光熔覆Al-Si合金,运用XRD、SEM、EDS等分析测试手段对合金层进行组织分析,并对合金层进行了显微硬度、耐磨性、耐腐蚀性等性能测试。研究表明激光熔覆Al-Si能够提高镁合金的硬度、耐磨性和耐腐蚀性。

Effect of Ni on microstructure and mechanical properties of Al−Mg−Si alloy for laser powder bed fusion

The microstructures and mechanical properties were systematically studied for the high-strength Al−5Mg_(2)Si−1.5Ni alloy fabricated by laser powder bed fusion(L-PBF).It is found that the introduction of Ni(1.5 wt.%)into an Al−5Mg_(2)Si alloy can significantly improve the L-PBF processibility and provide remarkable improvement in mechanical properties.The solidification range of just 85.5 K and the typical Al−Al3Ni eutectics could be obtained in the Ni-modified Al−5Mg_(2)Si samples with a high relative density of 99.8%at the volumetric energy density of 107.4 J/mm^(3).Additionally,the refined hierarchical microstructure was mainly characterized by heterogeneousα-Al matrix grains(14.6μm)that contain the interaction between dislocations and Al−Al3Ni eutectics as well as Mg_(2)Si particles.Through synergetic effects of grain refinement,dislocation strengthening and precipitation strengthening induced by Ni addition,the L-PBFed Al−5Mg_(2)Si−1.5Ni alloy achieved superior mechanical properties,which included the yield strength of(425±15)MPa,the ultimate tensile strength of(541±11)MPa and the elongation of(6.2±0.2)%.

相变介质组成对粉煤灰基高温定形复合相变材料蓄热性能的影响

分别以Al粉、Al-12Si、Al-20Si合金粉为相变介质,粉煤灰为基体材料,采用混合烧结法在空气、真空两种烧结氛围下制备金属/陶瓷基高温定形复合相变材料,探讨相变介质中硅铝相对含量及烧结氛围对材料蓄热性能的影响。结果表明:分别用三种金属粉制备复合相变材料时,Al的氧化难以避免,致使Si的相对含量均超过共晶点组成,凝固时其状态点始终处于共晶相+Si相的两相区,未被氧化的Al都转变成为Al-Si共晶相。空气中烧结有利于Al形成致密氧化膜从而阻止其进一步反应,材料的密度、相变潜热都比真空中烧结高。三种复合相变材料中,由Al粉制备的热稳定性最差,由Al-12Si合金粉制备的相变潜热、保留率最高,热稳定性及蓄热性能突出。