Revenue - Summary of Revenue by End-use Markets (Details) - USD ($) $ in Millions	12 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2022
Disaggregation of Revenue [Line Items]
Net sales	$ 2,759.7	$ 2,550.3	$ 1,836.3
Operating | Specialty Alloys Operations
Disaggregation of Revenue [Line Items]
Net sales	2,443.8	2,213.6	1,565.6
Operating | Performance Engineered Products
Disaggregation of Revenue [Line Items]
Net sales	411.0	433.7	344.5
Intersegment
Disaggregation of Revenue [Line Items]
Net sales	(95.1)	(97.0)	(73.8)
Aerospace and Defense
Disaggregation of Revenue [Line Items]
Net sales	1,538.8	1,290.7	790.2
Aerospace and Defense | Operating | Specialty Alloys Operations
Disaggregation of Revenue [Line Items]
Net sales	1,449.9	1,214.6	739.3
Aerospace and Defense | Operating | Performance Engineered Products
Disaggregation of Revenue [Line Items]
Net sales	111.1	108.0	76.7
Aerospace and Defense | Intersegment
Disaggregation of Revenue [Line Items]
Net sales	(22.2)	(31.9)	(25.8)
Medical
Disaggregation of Revenue [Line Items]
Net sales	375.6	301.6	212.3
Medical | Operating | Specialty Alloys Operations
Disaggregation of Revenue [Line Items]
Net sales	282.4	213.8	155.1
Medical | Operating | Performance Engineered Products
Disaggregation of Revenue [Line Items]
Net sales	144.9	123.4	79.9
Medical | Intersegment
Disaggregation of Revenue [Line Items]
Net sales	(51.7)	(35.6)	(22.7)
Transportation
Disaggregation of Revenue [Line Items]
Net sales	149.1	185.0	178.3
Transportation | Operating | Specialty Alloys Operations
Disaggregation of Revenue [Line Items]
Net sales	141.3	178.5	173.4
Transportation | Operating | Performance Engineered Products
Disaggregation of Revenue [Line Items]
Net sales	8.2	7.5	5.2
Transportation | Intersegment
Disaggregation of Revenue [Line Items]
Net sales	(0.4)	(1.0)	(0.3)
Energy
Disaggregation of Revenue [Line Items]
Net sales	185.8	163.3	113.0
Energy | Operating | Specialty Alloys Operations
Disaggregation of Revenue [Line Items]
Net sales	177.2	151.6	104.8
Energy | Operating | Performance Engineered Products
Disaggregation of Revenue [Line Items]
Net sales	8.6	11.6	8.1
Energy | Intersegment
Disaggregation of Revenue [Line Items]
Net sales	0.0	0.1	0.1
Industrial and Consumer
Disaggregation of Revenue [Line Items]
Net sales	415.3	487.2	417.2
Industrial and Consumer | Operating | Specialty Alloys Operations
Disaggregation of Revenue [Line Items]
Net sales	393.0	455.1	393.0
Industrial and Consumer | Operating | Performance Engineered Products
Disaggregation of Revenue [Line Items]
Net sales	40.3	60.6	49.1
Industrial and Consumer | Intersegment
Disaggregation of Revenue [Line Items]
Net sales	(18.0)	(28.5)	(24.9)
Distribution
Disaggregation of Revenue [Line Items]
Net sales	95.1	122.5	125.3
Distribution | Operating | Specialty Alloys Operations
Disaggregation of Revenue [Line Items]
Net sales	0.0	0.0	0.0
Distribution | Operating | Performance Engineered Products
Disaggregation of Revenue [Line Items]
Net sales	97.9	122.6	125.5
Distribution | Intersegment
Disaggregation of Revenue [Line Items]
Net sales	$ (2.8)	$ (0.1)	$ (0.2)