Nearest-to-Net Shape Molding
While many processes claim “net shape”, Liquidmetal® Injection Molding produces precision parts within very close tolerances directly from the mold thanks to the extremely low shrinkage rate of the material when it cools in its amorphous form. Shrinkage rate is published at 0.4% for the LM105 alloy, which is far less than metal die cast components (>0.6%) and plastic injection molded components. When compared to conventional Metal Injection Molding (MIM) processes, the MIM sintering step typically shrinks the “green state” part by 15-20%, which can cause warping and requires secondary machining to meet precision tolerances.
In addition to precision net-shape molding, an as-molded Liquidmetal part typically has a surface roughness of less than 0.05 µm (2 µin). This is a significant benefit compared with other processes that require additional processing to meet a surface spec of this quality. Die cast alloys and MIM components typically have surface roughness values that range from 0.8 – 1.6 µm (32 – 64 µin). Liquidmetal alloys’ atomic structure allows incredibly precise replication of tool surfaces, allowing very fine details, textures or highly polished surfaces to be imparted in a single step during high rate production.
Liquidmetal alloys are stronger than high-strength titanium, with yield strength of 1524 MPa (231 KSI). High-strength titanium (Ti-6Al-4V) has yield strength of 830 Mpa (120 KSI) and an ultimate tensile strength of only 900 Mpa (130 KSI). Like most glasses, the yield strength of Liquidmetal alloys are nearly identical to its ultimate tensile strength, meaning that when the material is stressed to its yield limit, rather than plastically deforming, it will break, and is therefore technically considered brittle, even though it is highly elastic (see below).
The exceptional strength of Liquidmetal alloys is more remarkable when compared with other metal molding or casting processes. The ultimate tensile strength of die cast materials (zinc, aluminum, and magnesium) does not exceed the 425 Mpa (62 KSI) mark.
Liquidmetal alloys also have a very high hardness, which can prove beneficial for parts that require a durable scratch and wear resistant surface. The hardness value of LM105 is 563 Vickers (53 HRC), which is significantly harder than conventional metal alloys. Die cast alloys can achieve hardness of 130 Vickers, Titanium (Ti-6Al-4V) can reach 340 Vickers (34 HRC), and Stainless Steel (17-4 PH) can reach 325 Vickers (33 HRC).
While Liquidmetal alloy may be more brittle than some high strength materials, LM105 can undergo 1.8% of elongation before reaching its yield point. This is driven by the material’s Elastic Modulus, which is 93 GPa, and its unique amorphous atomic structure. Other high strength materials tend to be much stiffer, reflecting their higher modulus of elasticity. Only Liquidmetal alloys can provide this unique combination of high strength and elasticity.
Liquidmetal alloys perform very well with no corrosion evident during a salt spray test conforming to ASTM standard B-117 for over 336 hours. When measured on a Scanning Electron Microscope at 5,000x magnification, there were no visible changes in surface quality.
In a 30-day immersion test, solutions were analytically diluted to 1 liter and inductively coupled plasma mass spectrometry was performed to determine elemental concentrations. In comparison with stainless steel, the Liquidmetal alloy experienced roughly 1/14th the dissolution in 1N HCl, and 1/5th the dissolution in 1N H2 SO4. Liquidmetal alloys excelled in the salt spray test, and well outperformed stainless steel in this 30-day acidic submersion test – as seen in the chart below.
The Liquidmetal team is continuing to pursue corrosion studies going forward, to further grasp the potential of the material.