For those of you that need to use materials (physical not visual) for your parts and assemblies that aren't in the Inventor standard template, this one is for you. I will also explain how you can apply specific hatch patterns per material in your drawings.
Lets take a look at how to add the materials you need. First, open a template file or part that you want to add a new material to. Open up the "Style Editor" from the Manage tab in the ribbon. Expand the Material node to show all the materials available in the part. If there is a material similar to what you would like to use, select it in the left portion on the dialog box and select New towards the top of the dialog box. Specify a new name and make the appropriate changes to the material. You can often find material properties by doing a Google/Bing search to locate a density table or any other properties you need.
Notice towards the bottom of the dialog box you can specify the color you want for this material.
Select done and we will proceed to the drawing environment to link up a hatch style to this material. Open a drawing or drawing template and navigate to the "Style Editor" just as we did in the part file. On the left pane select the standard you want to use (in my case I will use Default Standard (ANSI). Select the "Material Hatch Pattern Defaults" tab and either import materials from an existing file or bring in all the styles from an existing Style Library. Once imported you can select each material and apply a different hatch pattern to it that will be applied when you section your part/assembly.