Solid State Processing of Aluminum Matrix Composites Reinforced with Nanoparticulate Materials

Abstract

A simple powder metallurgy route is investigated at Empa for producing aluminum matrix nanocomposites. High energy ball milling has proven to be an efficient method for dispersing the nanoparticles into the matrix even up to high amount. The compaction of these blends at moderate temperature leads to dense nanocomposite materials with high strength whatever the nature of the reinforcement. Hot pressing, spark plasma sintering, and hot isostatic pressing induce the same tensile properties at rupture but higher yield strength can be observed for the simple hot pressing process. High strength can be only combined with high ductility for nanoparticle content below 1 vol%. These outstanding properties are achieved thanks to a homogenous nanoparticle dispersion as well as a bimodal grain size distribution with fine (<300 nm) and coarser grains (a few microns). The materials do not require subsequent heat or work hardening treatment and exhibit better or similar properties as the conventional high strength aluminum alloys. Finally, it is demonstrated that friction stir welding is a valuable process for joining these nanocomposites.

Carbon Nanotube‐Reinforced Aluminum Matrix Composites

“…The issues associated with liquid‐phase process such as agglomeration, nonuniform microstructure, and interfacial reaction at higher melt temperatures lead to detrimental effect on the properties of composites. This stimulated the researchers to seek alternate methods of processing MMCs . The other common way of blending the composites is solid‐state processing including PM‐based techniques.…”

“…This stimulated the researchers to seek alternate methods of processing MMCs. [52] The other common way of blending the composites is solid-state processing Figure 4. a) A TEM image of ball-milled CNTs used in a pressureless infiltration process, [45] b) HRTEM image showing Al 4 C 3 in Al matrix near the CNT/matrix interface in a friction stir processed 3 wt% CNT/AA2009, [46] c) silicon carbide layer on CNT surface in HVOF formed MWCNT/Al-Si composite, [47] d) TEM image showing the deformation of a CNT during cold spraying, [48] e) SEM image of CNT/Al composite powders with several typical CNTs (indicated by arrows) dispersed in Al powders by CVD, [49] f ) HRTEM image showing poor graphitization having reacted with Al at 650 C, [50] and g) the agglomerated CNTs and pores on the fracture surface of 1.8 vol% CNT/alumina nanocomposite.…”

Mechanical Anisotropy Investigated in the Complex SLM‐Processed Sc‐ and Zr‐Modified Al–Mg Alloy Microstructure

“…Based on a two‐tailed Student's t‐Test, the differences between the FG and CG regions are significant (95% confidence) for both <xy> and <xz>/<yz> planes for the as‐processed condition, and the <xy> plane of the annealed condition. For the as‐processed condition, as no intragranular Al 3 (Sc x ,Zr 1‐ x ) particle precipitation takes place within the utilized processing window, the hardness is affected by precipitation‐based strengthening from pre‐existing oxides, the local dislocation density, and grain boundary (GB) effects . As the nano‐indents have an indent side length which is larger than the typical FG dimension, a measurement within the FG region will deform several GBs.…”

A Cold-Pressing Method Combining Axial and Shear Flow of Powder Compaction to Produce High-Density Iron Parts

“…The possible reason why the quality of obtained preforms after single-load scheme of compaction cannot be sufficient at a pressure above 800 MPa can be specific zones of resistances-micron-sized cavities or macro-pores [44][45][46][47]. They can be interpreted as arch construction composed from particles that can withstand high stresses, when the load increases, the arch (of a pore) formed by adhesion and chemical bonds of atoms of particles' surface only becomes denser and stronger, this inhibits further preform compaction [20,31,32,34,48,49].…”