Microstructure and mechanical property of titanium-containing 6061 aluminum alloy prepared by selective laser melting

Abstract

The 6061 aluminium alloy is a heat treatable reinforced aluminium alloy containing magnesium and silicon as its main alloying elements. It is commonly used in the aerospace and automotive industries due to its excellent mass to strength ratio and high thermal conductivity, but is particularly susceptible to the formation of coarse columnar crystals and thermal tearing, particularly during SLM processing.TiH2/AA6061 aluminium-based composite powders were prepared by the low-energy ball milling assembly modification method, and the titanium-containing 6061 aluminum alloy specimens were prepared by selective laser melting technique.The microstructure and mechanical properties of the samples with different TiH2 contents were systematically investigates. The results show that the addition of 1% TiH2 (mass fraction, the same below) results in the formation of a continuous equiaxed crystal zone at the alloy melt pool boundary, the average grain size decreases from 59.8 μm to 2.53 μm, and the coarse columnar grains and cracks inhibit, and with the addition of 1.5% TiH2, the coarse columnar grains of the SLM specimens inhibit completely and only a few small columnar grains exist. The microstructure transformation is attributed to the enhancement of the constituent undercooling by Ti elements and the in-situ reaction to form L12-Al3Ti nucleation particles, which form a coherent interface with the Al matrix and have a strong heterogeneous nucleation effect, thus significantly promoting the transformation from columnar to equiaxed crystals and grain refinement of the Al matrix. After selective laser melting, the tensile strength of 6061 aluminum alloy with 1% TiH2 addition is 274 MPa, the yield strength is 238 MPa, and the elongation after break is 18%.

Keywords

• selective laser melting
• hot-tearing
• tih2
• 6061 aluminum alloy