Abstract
The effect of the addition ofAlB12particles to gravity cast Al-Zn alloys was studied and related to the composite deformation at high temperature. The characterization techniques of choice were thermomechanical analysis (TMA), Brinell hardness (HB), and optical microscopy. After homogenization treatment, Al-5 wt.% Zn and Al-10 wt.% Zn with 0, 2.08, 4.16 wt.% B samples were quenched in ice water and tested using a thermomechanical analyzer at different temperatures. It was found that after TMA treatment, Brinell hardness of the composites increased for higher concentrations of zinc andAlB12particles, as expected. Such increment was not, however, uniform for all samples at higher temperature levels, suggesting a nonequilibrium interaction between reinforcing particles and zinc. This was further corroborated by TMA experiments, which revealed that for samples with Al-10 wt.% Zn, high temperature deformation augmented as moreAlB12particles were present. After high temperature treatment, precipitation of zinc-rich allotriomorphs was observed by the optical microscopy performed on the samples near or on the aluminum grain boundaries, which discarded the potential effect of fine precipitation due to aging.
Highlights
Cast aluminum matrix composites have been widely used in the automotive and aerospace industry due to their weightto-strength ratio [1,2,3,4,5]
AlB2 particles are an alternative to SiC reinforcement particles in aluminum [6], because SiC/Al composites can have inconsistent wear resistance. is behavior has been attributed to the weak interface between SiC and the Al matrix [7] with potential deleterious aluminum carbide formation
We propose using a Zncontaining Al matrix reinforced with hard aluminum dodecaboride particles, which a prior research proved to strengthen aluminum solid solution matrices [10]
Summary
Cast aluminum matrix composites have been widely used in the automotive and aerospace industry due to their weightto-strength ratio [1,2,3,4,5]. Because of such application of these types of composites, studying their behavior at high temperatures is mandatory. Researchers demonstrated that the addition of hard boride particles to an aluminum matrix can enhance the composite strength. By adding hard boride particles to an Al matrix, the wear rate of the composite is lower when compared to unreinforced aluminum [2]. Such precipitation of a second phase improves hardness, Young’s modulus, and yield
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