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The microstructure evolution and mechanical properties under different temperature of as-cast Al-La alloys with varying La contents were investigated by X-ray diffraction (XRD), field-emission scanning electron microscope (FESEM), energy dispersive spectrometer (EDS) and tensile test (Gleeble 3500). The results revealed that the phase compositions of Al-xLa (x = 10, 15, 20) alloys were α-Al and Al 11 La 3 . Comparing with Al-10La, the mechanical properties of Al-15La and Al-20La were deteriorated due to the formation of strip-shaped and particle-shaped primary Al 11 La 3 phase respectively. The influence of Al 11 La 3 phase on tensile strength has a downward trend with the increasing temperature, and elevated temperature is more helpful to increase the plasticity of Al-La alloys with high La content. According to the tensile fracture of the three Al-La alloys at temperature range from 200 °C to 500 °C, Al-10La tended to be highly dimples driven, and dimples became larger and deeper with increasing temperature, which demonstrated a growing ability to avoid crack extension. There was a transformation from cleavages to dimples in Al-15La and Al-20La with increasing temperature, but the dimples were small and shallow indicating lower plasticity than Al-10La. [ABSTRACT FROM AUTHOR]

"SPS pre-sintering + SPS reactive hot extrusion" (SPSHE) is a promising technique for manipulating the orientation of TiB whiskers (TiBw) in discontinuously reinforced titanium matrix composites (DRTMCs). In the current study, (12.4 vol % TiBw +2.9 vol % TiC)/Ti6Al4V composites were prepared using SPSHE technology, successfully achieving both the normalization of TiBw orientation and a high aspect ratio. Specifically, the [010] axis of TiBw was aligned with the extrusion direction, and the average aspect ratio was 24.86. Tensile tests were conducted on the DRTMC samples at temperatures of 873 K, 923 K, and 973 K. The results demonstrate that SPSHE significantly enhances the high-temperature strength of the composite. At 873 K, the DRTMC exhibited an exceptionally high tensile strength of 732.2 ± 20 MPa. The main strengthening mechanisms of the DRTMC include load transfer strengthening from TiBw and TiC particles, solution strengthening, fine grain strengthening and dislocation strengthening. Moreover, at 873 K and 923 K, the dominant failure mode of the reinforcement was a load-bearing fracture. However, as the test temperature increased to 973 K, a mixed failure mode of load-bearing fracture and interface debonding was observed in the reinforcement. [ABSTRACT FROM AUTHOR]

In this work, 3.5 vol% TiB/Ti6Al4V composites with aligned TiB whiskers are synthesized by spark plasma sintering-hot extrusion (SPSHE). The effects of deformation temperature and deformation amount on the microstructure evolution and tensile properties are systematically investigated in composites. The results suggest that the dispersion of TiB whiskers is gradually improved with the deformation increasing from 30%, 50%–70%. TiB whiskers obtain a highly consistent orientation as the composite is deformed by 70%. The multiplication of more dislocations induced by TiB whiskers provides the driving force for dynamic recovery and dynamic recrystallization of the composite during SPSHE. In addition, the matrix microstructure of the composite is composed of α phase, β phase and interface L phase. The interface L phase decreases the mean free path of dislocation slip and improves the strength of the composite manipulated by SPSHE. The tensile strength (1294 ± 20 MPa) and elongation (5.0% ± 0.5%) of the composite with a deformation amount of 70% at 950 °C are well combined. According to the analysis results of the microstructure and fracture, the strengthening mechanism of the composite is the TiB load transfer strengthening effect and the matrix strengthening effects including interface L phase strengthening, fine grain strengthening, substructure strengthening and texture strengthening. [ABSTRACT FROM AUTHOR]