<p>Aluminum alloys
have broad applications in aerospace, automotive, and defense industries as
structural material due to the low density, high-specific strength, good
castability and formability. However,
aluminum alloys commonly suffer from problems such as low yield strength, low
stiffness, and poor wear and tear resistance, and therefore are restricted to
certain advanced industrial applications. To overcome the problems, one
promising method is the fabrication of aluminum matrix composites (AMCs) by
introducing ceramic reinforcements (fibers, whiskers or particles) in the metal
matrix. AMCs typically possess advanced properties than the matrix alloys such
as high specific modulus, strength, wear resistance, thermal stability, while
remain the low density. Among the AMCs, particulate reinforced aluminum matrix
composites (PRAMCs) are advantageous for their isotropic properties, ease of
fabrication, and low costs. Particularly, the PRAMCs with in-situ particulate
reinforcements have received great interest recent years. The in-situ
fabricated particles are synthesized in an aluminum matrix via chemical
reactions. They are more stable and finer in size, and have a more uniform
distribution in the aluminum matrix and stronger interface bonding with
aluminum matrix, compared to the ex-situ particulate reinforcements. As a consequence,
the in-situ PRAMCs have superior strength and mechanical properties as advanced
engineering materials for a broad range of industrial applications.</p>
<p>This dissertation
focuses on the investigation of high strength aluminum matrix composites
reinforced with in-situ particulates. The first chapter provides a brief
introduction for the studied materials in the dissertation, including the
background, the scope, the significance and the research questions of the
study. The second chapter presents the literature review on the basic
knowledge, the fabrication methods, the mechanical properties of in-situ
PRAMCs. The strengthening mechanisms and strategies of in-situ PRAMCs are
summarized. Besides, the micromechanical simulation is introduced as a
complementary methodology for the investigation of the
microstructure-properties relationship of the in-situ PRAMCs. The third chapter
shows the framework and methodology of this dissertation, including material
preparation and material characterization methods, phase diagram method and
finite element modelling. </p>
<p>In Chapter 4,
the microstructures and mechanical properties of in-situ Al<sub>3</sub>Ti
particulate reinforced A356 composites are investigated. The microstructure and
mechanical properties of in-situ 5 vol. % Al<sub>3</sub>Ti/A356 composites are
studied either taking account of the effects of T6 heat treatment and strontium
(Sr) addition or not. Chapter 5 studies the evolution of intermetallic phases
in the Al-Si-Ti alloy during solution treatment, based on the work of Chapter
4. The as-cast Al-Si-Ti alloy is solution treated at 540 °C for different
periods between 0 to 72 h to understand the evolution of intermetallic phases.
In Chapter 6, a three-dimensional (3D) micromechanical simulation is conducted
to study the effects of particle size, fraction and distribution on the
mechanical behavior of the in-situ Al<sub>3</sub>Ti/A356 composite. The
mechanical behavior of the in-situ Al<sub>3</sub>Ti/A356 composite is studied
by three-dimensional (3D) micromechanical simulation with microstructure-based
Representative Volume Element (RVE) models. The effects of hot rolling and heat
treatment on the microstructure and mechanical properties of an in-situ TiB<sub>2</sub>/Al2618 composite
with minor Sc addition are investigated in Chapter 7. TiB<sub>2</sub>/Al2618 composites ingots were fabricated <i>in-situ</i> via salt-melt reactions and
subjected to hot rolling. The microstructure and mechanical properties of the TiB<sub>2</sub>/Al2618 composite are
investigated by considering the effects of particle volume fraction, hot
rolling thickness reduction, and heat treatment. </p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/14498514 |
| Date | 06 May 2021 |
| Creators | Siming Ma (10712601) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/thesis/HIGH_STRENGTH_ALUMINUM_MATRIX_COMPOSITES_REINFORCED_WITH_AL3TI_AND_TIB2_IN-SITU_PARTICULATES/14498514 |
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