The effect of Mn content on the microstructure evolution and mechanical properties of Al–Cu–Mg–x Mn alloys at ambient temperature was investigated. The findings show that in the Mn-containing alloys at the as-cast state, the blocky primary T(Al₂₀Cu₂Mn₃) phase coexisting with the Al₂Cu phase appeared. With the increase in Mn content, the majority of the Al₂Cu phase dissolved, nd a minor amount of the T phase remained at the grain boundary after solution treatment. The rod-like T_Mn (Al₂₀Cu₂Mn₃) nanoprecipitate was simultaneously distributed at grain boundaries and the interiors, while a high density of needle-like θ″ (Al₃Cu) nanoprecipitate was also observed in the T6 state. Further increases in Mn content promoted the dispersion of the T_Mn phase and inhibited the growth and transformation of the θ″ phase. Tensile test results show that 0.7 wt.% Mn alloy had excellent mechanical properties at ambient temperature with ultimate tensile strength, yield strength, and fracture elongation of 498.7 MPa, 346.2 MPa, and 19.2%, respectively. The subsequent calculation of strengthening mechanisms elucidates that precipitation strengthening is the main reason for the increase in yield strength of Mn-containing alloys.

Precipitation coarsening characteristics at elevated temperature have a powerful influence on the thermodynamics properties of TiB₂ particles reinforced aluminium-copper matrix composites (PRAMCs), aging precipitation of θ-Al₂Cu is stable at room temperature, but coarsening occurs at elevated temperature, In this paper, Al-4.5Cu matrix composites with different content TiB₂ are prepared via the molten salt reaction to evaluate the microstructures transformation and the related elevated temperature mechanical properties. Experimental results show that yield strength (YS) and ultimate tensile strength (UTS) of TiB₂/Al-4.5Cu composites increase with the augment of TiB₂ mass fraction, while the elongation decreases gradually both at elevated-temperature of 453k and 493k. The analysis suggests that the remarkable α-Al grain refinement along with pinning effect of TiB₂ particles has a great effect on the grain boundary sliding and migration at high temperature. Additionally, interface debonding also affects the damage and fracture of the composites.

Mechanical performance of TiB₂/Al-4.5%Cu composites at elevated-temperature were evaluated by means of tensile behaviors and fracture mechanisms. Results indicated that the composite reinforced by nano-sized TiB₂ particles exhibited excellent mechanical ability during deformation at elevated temperatures, the optimum addition level for dispersion, refinement and modification was 5wt.% TiB₂/Al-4.5%Cu at 473K, i.e., yield strength is 358MPa and elongation is 4 %. The enhanced resistance of the composite was mainly attributed to Orowan strengthening and load transfer enhancement, additionally, interface debonding increasingly affects the damage and fracture of the composites.