Microstructural Analysis of the Reinforced Al‐Cu5mgti/Tib₂ 5 wt % Alloy for Investment Casting Applications

Abstract

The Al-Cu5MgTi alloy is a heat treatable alloy that presents good machining properties. It is mainly used in aircraft parts when better mechanical properties than those provided by Al-Si alloys such as Al-Si7Mg0.3 are required. Nevertheless it is not so extensively applied as the latter due to its lower castability. Its solidification range is very large and this makes it prone to hot tearing related problems. The Al-Cu5MgTi alloy is mainly applied when high mechanical properties are needed at high temperatures. Magnesium alloying increases the strength and hardness of this alloy through thermal treatment and titanium is used as a grain refiner so that the insoluble constituents can be better dispersed as well as the porosity and defect distribution decrease.The use of grain refiners in these alloys is highly recommended due to the clear benefits they provide. The hot tearing related problems become reduced, mechanical properties get improved, and surface quality and the response to thermal treatments is better. Al-Ti-B type grain refiners have been used with this alloy in different foundry processes. Their use is even more essential in the case of low cooling rate processes like sand casting or lost wax processes as the large solidification intervals of the alloy (450-650 8C) [1] tends to create problems related to hot tearing and poor mechanical properties.TiB 2 particles incorporated in Al-Ti-B grain refiners are extensively used by aluminum foundries to promote heterogeneous nucleation and formation of equiaxed microstructure thus to improve the mechanical properties of the castings. The addition of only 0.15 wt% TiB 2 is enough to get a significant refinement of the grains. [2,3] Even though the main effect of the addition of TiB 2 particles into aluminum alloys is the refinement of the aluminum grains, there are other additional microstructural changes such as an increase in the modulus and ductility of the base alloy as well as a change in the thermal properties that can also be explained by the presence of these particles. The alloy studied in this work contains up to 5 wt% of TiB 2 particles. This amount largely exceeds the levelThe paper describes the influence of 5 wt % titanium diboride (TiB 2 ) particles on the microstructure of an Al-Cu alloy produced by plaster casting process. The elaboration route leads to a composite material with 1% of in situ TiB 2 particles and 4% ex situ of TiB 2 particles. The comparison of the reinforced alloy with the corresponding non-reinforced counterpart makes clear that the presence of TiB 2 particles has a large influence in the observed microstructure. The presence of TiB 2 particles decreases the grain sizes and the porosity level. It is also found that TiB 2 particles play an important role in the precipitation events of Al 2 Cu precipitates that are formed during solidification at the TiB 2 /aluminum matrix interfaces.504

Achieving Superior Strength–Ductility–Conductivity Combination in TiB2p/6201 Composites via Particle Rotation and Subgrain Refinement

“…In situ synthesized by the halide salt reaction method, [14][15][16][17][18][19] TiB 2 particles are the favorable reinforcement among many ceramic particles in PRAMCs. [20][21][22] This method is of great industrial interest because it can be easily integrated into the flow of foundry metallurgy and downstream processes to realize a massive production.…”

Analysis of the Solidification and Microstructure of Two Aluminium Alloys Reinforced with TiB2 Particles

“…Due to its inertness and good wetting behaviour with aluminium, TiB 2 can also be used as a reinforcing phase in metal matrix composites (MMCs). [1][2][3][4][5][6] When the amount of TiB 2 incorporated is increased in order to reinforce the materials, other solidification-related phenomena appear. In particular, TiB 2 particles are insoluble in aluminium and do not react chemically with it, but it has been observed that some solidification characteristics of the alloy are affected by the addition of TiB 2 : solidification events start earlier due to the lower undercooling required and the solidification time is reduced.…”